Emerging Multifunctional Metal-Organic Framework Materials

Rationally Integrating Charge-Transfer Cocrystal and Ni(II) Organometallics for Visualized Photo/Thermochromic Sensors

Smart materials demonstrate fascinating responses to environmental physical/chemical stimuli, including thermal, photonic, electronic, humidity, or magnetic stimuli, which have attracted intensive interest in material chemistry. However, their limited/harsh stimuli-responsive behavior or sophisticated postprocessing leads to enormous challenges for practical applications. Herein, we rationally designed and synthesized thermochromic Ni(II) organometallic [(C2H5)2NH2]2NiCl4-xBrx via a facile mechanochemical strategy, which demonstrated a reversible switch from yellow to blue color with a tunable phase-transition temperature from 75.6 to 61.7 °C. The simple electrospinning technology was applied to fabricate thermochromic Ni(II) organometallic-based nanofiber membranes for temperature monitoring. Furthermore, the organic charge-transfer cocrystal with a wide spectral absorption of 300-1950 nm and a high-efficiency photothermal conversion was combined with thermochromic Ni(II) organometallics for the desired dual-stimuli photo/thermochromism. This work supplies a new strategy for realizing multiple stimuli-responsive applications, such as thermal/light sensor displays and information storage.

Detection of acetaminophen and P-aminophenol simultaneously by an electrochemical sensor based on Fe-NC derivatives attached with Ti3C2 QDs

In this paper, Ti3C2 QDs and Fe-ZIF-8 were synthesized by a straightforward hydrothermal method. Fe-ZIF-8 was pyrolyzed at high temperatures to obtain Fe-nanoclusters (Fe-NC). Then Fe-NC is mixed with Ti3C2 QDs to form a new composite material (Ti3C2 QDs/Fe-NC), and its microstructure and composition were analyzed by technology. The proposed material can detect acetaminophen (PA) and P-aminophenol (4-AP) simultaneously with excellent detection performance. With the best conditions, the linear ranges and detection limits were 0.50-210.00 μM, 0.03 μM (S/N = 3) and 0.50-150.00 μM, 0.06 μM (S/N = 3) for PA and 4-AP, respectively. The sensor has lower detection limits and wider linear ranges, and can successfully detect 4-AP and PA in river water and acetaminophen tablets at the same time, showing potential practical application prospects. Especially, this study reports the modification of MOF derivatives with Ti3C2 QDs for the first time, which expands the application scope of Quantum Dots and MOF derivatives.

A Co-MOF encapsulated microneedle patch activates hypoxia induction factor-1 to pre-protect transplanted flaps from distal ischemic necrosis

Avoiding ischemic necrosis after flap transplantation remains a significant clinical challenge. Developing an effective pretreatment method to promote flap survival postoperatively is crucial. Cobalt chloride (CoCl2) can increase cell tolerance to ischemia and hypoxia condition by stimulating hypoxia-inducible factor-1 (HIF-1) expression. However, the considerable toxic effects severely limit the clinical application of CoCl2. In this study, cobalt-based metal-organic frameworks (Co-MOF) encapsulated in a microneedle patch (Co-MOF@MN) was developed to facilitate the transdermal sustained release of Co2+ for rapid, minimally invasive rapid pretreatment of flap transplantation. The MN patch was composed of a fully methanol-based two-component cross-linked polymer formula, with a pyramid structure and high mechanical strength, which satisfied the purpose of penetrating the skin stratum corneum of rat back to achieve subcutaneous vascular area administration. Benefiting from the water-triggered disintegration of Co-MOF and the transdermal delivery via the MN patch, preoperative damage and side effects were effectively mitigated. Moreover, in both the oxygen-glucose deprivation/recovery (OGD/R) cell model and the rat dorsal perforator flap model, Co-MOF@MN activated the HIF-1α pathway and its associated downstream proteins, which reduced reperfusion oxidative damage, improved blood supply in choke areas, and increased flap survival rates post-transplantation. This preprotection strategy, combining MOF nanoparticles and the MN patch, meets the clinical demands for trauma minimization and uniform administration in flap transplantation. STATEMENT OF SIGNIFICANCE: Cobalt chloride (CoCl2) can stimulate the expression of hypoxia-inducible factor (HIF-1) and improve the tolerance of cells to ischemia and hypoxia conditions. However, the toxicity and narrow therapeutic window of CoCl2 severely limit its clinical application. Herein, we explored the role of Co-MOF as a biocompatible nanocage for sustained release of Co2+, showing the protective effect on vascular endothelial cells in the stress model of oxygen-glucose deprivation. To fit the clinical needs of minimal trauma in flap transplantation, a Co-MOF@MN system was developed to achieve local transdermal delivery at the choke area, significantly improving blood supply opening and flap survival rate. This strategy of two-step delivery of Co2+ realized the enhancement of biological functions while ensuring the biosafety.

Recent advances in molecularly imprinted polymers (MIPs) for visual recognition and inhibition of α-dicarbonyl compound-mediated Maillard reaction products

α-Dicarbonyl compounds (α-DCs) are important intermediates and precursors of harmful Maillard reaction products (e.g., acrylamide and late glycosylation end-products), and they exist widely in thermoprocessed sugar- or fat-rich foods. α-DCs and their end-products are prone to accumulation in the human body and lead to the development of various chronic diseases. Therefore, detection of α-DCs and their associated hazards in food samples is crucial. This paper reviews the preparation of molecularly imprinted polymers (MIPs) enabling visual intelligent responses and the strategies for recognition and capture of α-DCs and their associated hazards, and provides a comprehensive summary of the development of visual MIPs, including integration strategies and applications with real food samples. The visual signal responses as well as the mechanisms for hazard recognition and capture are highlighted. Current challenges and prospects for visual MIPs with advanced applications in food, agricultural and environmental samples are also discussed. This review will open new horizons regarding visual MIPs for recognition and inhibition of hazards in food safety.

Porous organic crystals crosslinked by free-radical reactions

Two hydrogen-bonded crosslinked organic frameworks (HCOFs) were synthesized via free radical reactions utilizing butadiene and isoprene as crosslinkers. These HCOFs exhibit high crystallinity, enabling detailed structural characterization via single-crystal X-ray diffraction analysis. Subsequently, one of the olefin-rich HCOFs was converted to a hydroxylated framework through hydroboration-oxidation while maintaining the high crystallinity.

Metal-Organic Frameworks-Based Frustrated Lewis Pairs for Selective Reduction of Nitroolefins to Nitroalkanes

Nitroalkanes serve as essential intermediates in the synthesis of pharmaceuticals, agrochemicals, and functional materials. To date, nitroalkanes are mainly prepared from homogeneous catalysts such as noble transition metal catalysts with poor recyclability. Herein, we propose a metal-organic framework-frustrated Lewis pair (MOF-FLP) heterogeneous catalyst for selectively reducing nitroolefins to nitroalkanes under moderate reaction conditions. MOF enrichment effect can significantly improve the catalytic efficiency compared to homogeneous FLP catalysts. Benefiting from the strong interaction between FLP and MOF, the MOF-FLP catalyst exhibits outstanding recyclability. This work not only provides a convenient route for nitroalkane synthesis but also showcases the potential of porous heterogeneous FLP catalysts, offering inspiration for future catalytic design strategies.

Amorphous Engineering of Scalable Metal-Organic Framework-Derived Electrocatalyst for Highly Efficient Oxygen Evolution Reaction

The engineering of amorphous metal-organic frameworks (MOFs) offers potential opportunities for the construction of electrocatalysts for efficient oxygen evolution reaction (OER). Herein, highly efficient OER performance and durability in alkaline electrolyte are discovered for MOF-derived amorphous and porous electrocatalysts, which are synthesized in a brief procedure and can be facilely produced in scalable quantities. The structural inheritance of MOF amorphous catalysts is significant for the retention of catalytic sites and the diffusion of electrolytes, and the presence of Fe sites can change the electronic structure and effectively control the adsorption behavior of important intermediates, accelerating reaction kinetics. The obtained amorphous A-FeNi can be transformed from FeNi-MOF effortlessly and instantly, and it only needs low overpotentials of 152 and 232 mV at 10 and 100 mA cm-2 with a Tafel slope of 17 mV dec-1 in 1 m KOH for OER. Moreover, A-FeNi possesses high corrosion resistance and durability, therefore A-FeNi can work continually for at least 400 h at 100 mA cm-2. This work may pave a new avenue for the design of MOFs-related amorphous electrocatalyst.

Central Metal-Triggered Structural Transformation of a 2D Layered MOF: Mechanistic Studies and Applications

The structural transformation of metal-organic frameworks (MOFs) has attracted increasing interests, which has not only produced various new structures but also served as a fantastic platform for MOF-based kinetic analysis. Multiple reaction conditions have been documented to cause structural transformation; nevertheless, central metal-induced topological alteration of MOFs is rare. Herein, we reported a structural transformation of a 2D layered Cd-MOF driven by Cd(II) ions. After being submerged in the aqueous solution of cadmium nitrate, the twofold interpenetrated 2D network of [Cd(hsb-2)(bdc)·5H2O]n [HSB-W10; bdc: 1,4-benzenedicarboxylate; hsb-2:1,2-bis(4'-pyridylmethylamino)-ethane] was converted into a novel noninterpenetrated 2D network [Cd1.5(hsb-2)(bdc)1.5(H2O)2·H2O]n (HSB-W16). This partial dissolution-recrystallization process was investigated by integrating controlled experiments, 1H NMR spectra, and photographic tracking analysis. Furthermore, a novel strategy combining in situ multicomponent dye encapsulation and central metal-triggered structural transformation was developed for the fabrication of MOF materials with white-light emission. By adopting this strategy, different dye guest molecules were concurrently introduced into the HSB-W16 host matrix, leading to a range of white-light-emitting MOF composites. This work will enable detailed studies of solid-state transformations and demonstrate a promising application prospect for structural transformation.

A multifunctional protein pre-coated metal-organic framework for targeted delivery with deep tissue penetration

Targeted drug delivery using metal-organic frameworks (MOFs) has shown significant progress. However, the tumor microenvironment (TME) impedes efficient MOF particle transfer into tumor cells. To tackle this issue, we pre-coated nano-sized MOF-808 particles with multifunctional proteins: glutathione S-transferase (GST)-affibody (Afb) and collagenase, aiming to navigate the TME more effectively. The surface of MOF-808 particles is coated with GST-Afb-a fusion protein of GST and human epidermal growth factor receptor 2 (HER2) Afb or epidermal growth factor receptor (EGFR) Afb which has target affinity. We also added collagenase enzymes capable of breaking down collagen in the extracellular matrix (ECM) through supramolecular conjugation, all without chemical modification. By stabilizing these proteins on the surface, GST-Afb mitigate biomolecule absorption, facilitating specific tumor cell targeting. Simultaneously, collagenase degrades the ECM in the TME, enabling deep tissue penetration of MOF particles. Our resulting system, termed collagenase-GST-Afb-MOF-808 (Col-Afb-M808), minimizes undesired interactions between MOF particles and external biological proteins. It not only induces cell death through Afb-mediated cell-specific targeting, but also showcases advanced cellular internalization in 3D multicellular spheroid cancer models, with effective deep tissue penetration. The therapeutic efficacy of Col-Afb-M808 was further assessed via in vivo imaging and evaluation of tumor inhibition following injection of IR-780 loaded Col-Afb-M808 in 4T1tumor-bearing nude mice. This study offers key insights into the regulation of the multifunctional protein-adhesive surface of MOF particles, paving the way for the designing even more effective targeted drug delivery systems with nano-sized MOF particles.

Support based metal incorporated layered nanomaterials for photocatalytic degradation of organic pollutants

An effective approach to producing sophisticated miniaturized and nanoscale materials involves arranging nanomaterials into layered hierarchical frameworks. Nanostructured layered materials are constructed to possess isolated propagation assets, massive surface areas, and envisioned amenities, making them suitable for a variety of established and novel applications. The utilization of various techniques to create nanostructures adorned with metal nanoparticles provides a secure alternative or reinforcement for the existing physicochemical methods. Supported metal nanoparticles are preferred due to their ease of recovery and usage. Researchers have extensively studied the catalytic properties of noble metal nanoparticles using various selective oxidation and hydrogenation procedures. Despite the numerous advantages of metal-based nanoparticles (NPs), their catalytic potential remains incompletely explored. This article examines metal-based nanomaterials that are supported by layers, and provides an analysis of their manufacturing, procedures, and synthesis. This study incorporates both 2D and 3D layered nanomaterials because of their distinctive layered architectures. This review focuses on the most common metal-supported nanocomposites and methodologies used for photocatalytic degradation of organic dyes employing layered nanomaterials. The comprehensive examination of biological and ecological cleaning and treatment techniques discussed in this article has paved the way for the exploration of cutting-edge technologies that can contribute to the establishment of a sustainable future.

Unveiling the Power of Cloaking Metal-Organic Framework Platforms via Supramolecular Antibody Conjugation

Targeted drug delivery systems based on metal-organic frameworks (MOFs) have progressed tremendously since inception and are now widely applicable in diverse scientific fields. However, translating MOF agents directly to targeted drug delivery systems remains a challenge due to the biomolecular corona phenomenon. Here, we observed that supramolecular conjugation of antibodies to the surface of MOF particles (MOF-808) via electrostatic interactions and coordination bonding can reduce protein adhesion in biological environments and show stealth shields. Once antibodies are stably conjugated to particles, they were neither easily exchanged with nor covered by biomolecule proteins, which is indicative of the stealth effect. Moreover, upon conjugation of the MOF particle with specific targeted antibodies, namely, anti-CD44, human epidermal growth factor receptor 2 (HER2), and epidermal growth factor receptor (EGFR), the resulting hybrid exhibits an augmented targeting efficacy toward cancer cells overexpressing these receptors, such as HeLa, SK-BR-3, and 4T1, as evidenced by flow cytometry. The therapeutic effectiveness of the antibody-conjugated MOF (anti-M808) was further evaluated through in vivo imaging and the assessment of tumor inhibition effects using IR-780-loaded EGFR-M808 in a 4T1 tumor xenograft model employing nude mice. This study therefore provides insight into the use of supramolecular antibody conjugation as a promising method for developing MOF-based drug delivery systems.

Three-Component Construction of Mesoporous Metal-Organic Frameworks and Their Incorporation into Solid Polymer Electrolytes for Li-Ion Conduction

Solid electrolytes with high ionic conductivity and satisfactory electrochemical stability are essential for the development of solid-state batteries. However, current strategies, including polymer (and polymer-based composite) electrolytes, still face challenges in meeting the bar set by real operations. We seek to improve the Li-ion conduction of the electrolytes by incorporating mesoporous metal-organic frameworks (MOFs) into the polymer matrix. Specifically, MOFs with pores larger than 3.0 nm are constructed by three-component reactions that involve the construction of both coordinative and dynamic imine linkages. The MOFs allow polymer penetration and amorphization and efficient lithium salt dissociation in the confined channels. Numerous metal sites and organic functionalities in the MOF backbone further assist the ion migration by providing strong interactions with the fluorinated polymer and the Li+. Remarkable ionic conductivity (0.95 mS cm-1) and a large lithium transference number (0.64) are achieved. Overall, the study fully utilizes both the MOF structural units with atomic precision and the encompassed space at the mesoscale for solid-state electrolyte development.

Promoted hydrogenation of CO2 to methanol over single-atom Cu sites with Na+-decorated microenvironment

Although single-atom Cu sites exhibit high efficiency in CO2 hydrogenation to methanol, they are prone to forming Cu nanoparticles due to reduction and aggregation under reaction conditions, especially at high temperatures. Herein, single-atom Cu sites stabilized by adjacent Na+ ions have been successfully constructed within a metal-organic framework (MOF)-based catalyst, namely MOF-808-NaCu. It is found that the electrostatic interaction between the Na+ and Hδ- species plays a pivotal role in upholding the atomic dispersion of Cu in MOF-808-NaCu during CO2 hydrogenation, even at temperatures of up to 275°C. This exceptional stabilization effect endows the catalyst with excellent activity (306 g·kgcat-1·h-1), high selectivity to methanol (93%) and long-term stability at elevated reaction temperatures, far surpassing the counterpart in the absence of Na+ (denoted as MOF-808-Cu). This work develops an effective strategy for the fabrication of stable single-atom sites for advanced catalysis by creating an alkali-decorated microenvironment in close proximity.

Applications of Metals and Metal Compounds in Improving the Sensitivity of Microfluidic Biosensors - A Review

The enhancement of detection sensitivity in microfluidic sensors has been a continuously explored field. Initially, many strategies for sensitivity improvement involved introducing enzyme cascade reactions, but enzyme-based reactions posed challenges in terms of cost, stability, and storage. Therefore, there is an urgent need to explore enzyme-free cascade amplification methods, which are crucial for expanding the application range and improving detection stability. Metal or metal compound nanomaterials have gained great attention in the exploitation of microfluidic sensors due to their ease of preparation, storage, and lower cost. The unique physical properties of metallic nanomaterials, including surface plasmon resonance, surface-enhanced Raman scattering, metal-enhanced fluorescence, and surface-enhanced infrared absorption, contribute significantly to enhancing detection capabilities. The metal-based catalytic nanomaterials, exemplified by Fe3O4 nanoparticles and metal-organic frameworks, are considered viable alternatives to biological enzymes due to their excellent performance. Herein, we provide a detailed overview of the applications of metals and metal compounds in improving the sensitivity of microfluidic biosensors. This review not only highlights the current developments but also critically analyzes the challenges encountered in this field. Furthermore, it outlines potential directions for future research, contributing to the ongoing development of microfluidic biosensors with improved detection sensitivity.

A Copper-Based Metal-Organic Framework for Selective Separation of C2 Hydrocarbons from Methane at Ambient Conditions: Experiment and Simulation

C2 hydrocarbon separation from methane represents a technological challenge for natural gas upgrading. Herein, we report a new metal-organic framework, [Cu2L(DEF)2]·2DEF (UNT-14; H4L = 4,4',4″,4‴-((1E,1'E,1″E,1‴E)-benzene-1,2,4,5-tetrayltetrakis(ethene-2,1-diyl))tetrabenzoic acid; DEF = N,N-diethylformamide; UNT = University of North Texas). The linker design will potentially increase the surface area and adsorption energy owing to π(hydrocarbon)-π(linker)/M interactions, hence increasing C2 hydrocarbon/CH4 separation. Crystallographic data unravel an sql topology for UNT-14, whereby [Cu2(COO)4]···[L]4- paddle-wheel units afford two-dimensional porous sheets. Activated UNT-14a exhibits moderate porosity with an experimental Brunauer-Emmett-Teller (BET) surface area of 480 m2 g-1 (vs 1868 m2 g-1 from the crystallographic data). UNT-14a exhibits considerable C2 uptake capacity under ambient conditions vs CH4. GCMC simulations reveal higher isosteric heats of adsorption (Qst) and Henry's coefficients (KH) for UNT-14a vs related literature MOFs. Ideal adsorbed solution theory yields favorable adsorption selectivity of UNT-14a for equimolar C2Hn/CH4 gas mixtures, attaining 31.1, 11.9, and 14.8 for equimolar mixtures of C2H6/CH4, C2H4/CH4, and C2H2/CH4, respectively, manifesting efficient C2 hydrocarbon/CH4 separation. The highest C2 uptake and Qst being for ethane are also desirable technologically; it is attributed to the greatest number of "agostic" or other dispersion C-H bond interactions (6) vs 4/2/4 for ethylene/acetylene/methane.

Topology Prediction of Gas-Separating Metal-Organic Frameworks with Low Symmetry Vertices

Topology serves as a blueprint for the construction of reticular structures such as metal-organic frameworks, especially for those based on building blocks with highly symmetrical shapes. However, it remains a challenge to predict the topology of the frameworks from less symmetrical units, because their corresponding vertex figures are largely deformed from the perfect geometries with no "default" net embedding. Furthermore, vertices involving flexible units may have multiple shape choices, and the competition among their designated topologies makes the structure prediction in large uncertainty. Herein, the deformation index is proposed to characterize the symmetry loss of the vertex figure by comparing it with its ideal geometry. The mathematical index is employed to predict the shapes of two in situ formed Co-based metalloligands (pseudo-tetrahedron and pseudo-square), which further dictate the framework topology (flu and scu) when they are joined with the [Zr6O8]-based cuboid units. The two frameworks with very similar constituents provide an ideal platform to investigate how the pore shapes and interconnectivity influence the gas separation. The net with cylindrical channels outperforms the other with discreate cages in C3H8/C2H6/CH4 separation, benefiting from the facile accessibility of its interaction sites to the guests imposed by the specific framework topology.

In-situ growth of metal-organic frameworks on cellulose nanofiber aerogels for rapid adsorption of heterocyclic aromatic amines

Heterocyclic aromatic amines (HAAs) are the main carcinogens produced during thermal processing of protein-rich foods. In this paper, a composite aerogel (TOCNFCa) with a stabilized dual-network structure was prepared via a template for the in-situ synthesis of UiO-66 on cellulose for the adsorption of HAAs in food. The dual-network structure of TOCNFCa provides the composite aerogel with excellent wet strength, maintaining excellent compressive properties. With the in-situ grown UiO-66 content up to 71.89 wt%, the hierarchical porosity endowed TOCNFCa@UiO-66 with the ability to rapidly adsorb HAAs molecules with high capacity (1.44-5.82 μmol/g). Based on excellent thermal stability, adsorption capacity and anti-interference, TOCNFCa@UiO-66 achieved satisfactory recoveries of HAAs in the boiled marinade, which is faster and more economical than the conventional SPE method. Moreover, TOCNFCa@UiO-66 could maintain 84.55 % of the initial adsorption capacity after 5 times of reuse.

A Functionally Asymmetric Janus Hygro-Photothermal Hybrid for Atmospheric Water Harvesting in Arid Regions

Metal-organic frameworks (MOFs) are high-performance adsorbents for atmospheric water harvesting but have poor water-desorption ability, requiring excess energy input to release the trapped water. Addressing this issue, a Janus-structured adsorbent with functional asymmetry is presented. The material exhibits contrasting functionalities on either face - a hygroscopic face interfaced with a photothermal face. Hygroscopic aluminum fumarate MOF and photothermal CuxS layers are in-situ grown on opposite sides of a Cu/Al bimetallic substrate, resulting in a CuxS-Cu/Al-MOF Janus hygro-photothermal hybrid. The two faces serve as independent "factories" for photothermal conversion and water adsorption-desorption respectively, while the interfacing bimetallic layer serves as a "heat conveyor belt" between them. Due to the high porosity and hydrophilicity of the MOF, the hybrid exhibits a water-adsorption capacity of 0.161 g g-1 and a fast adsorption rate (saturation within 52 min) at 30% relative humidity. Thanks to the photothermal CuxS, the hybrid can reach 71.5 °C under 1 Sun in 20 min and desorb 97% adsorbed water in 40 min, exhibiting a high photothermal conversion efficiency of over 90%. CuxS-Cu/Al-MOF exhibits minimal fluctuations after 200 cycles, and its water-generation capacity is 3.21 times that of powdery MOF in 3 h in a self-designed prototype in one cycle.

High-Performance Ni3(HHTP)2 Film-Based Flexible Field-Effect Transistor Gas Sensors

Conductive metal-organic frameworks (MOFs) have received increasing attention in recent years and present high application potential as sensing elements in electronic sensors. In this study, flexible field-effect transistor (FET) sensors based on conductive MOF, i.e., Ni3(HHTP)2, have been constructed. This Ni3(HHTP)2 sensor has high sensitivity (detection limit of 56 ppb) as well as superior selectivity for NO2 detection at room temperature, which is demonstrated by accurate gas detection in a mixed gas atmosphere. Moreover, by employing six flexible substrates, i.e., polyimide (PI), tape (PET), facemask, paper cup, tablecloth, and take-out bag (textile), we successfully demonstrate the universality of the flexible sensor construction with conductive MOF as sensing film on various substrates. This study of conductive MOF-based flexible electronic sensors offers a new opportunity for a wide range of sensing applications with wearable and portable electronic devices.

From nano- to macroarchitectures: designing and constructing MOF-derived porous materials for persulfate-based advanced oxidation processes

Persulfate-based advanced oxidation processes (PS-AOPs) have gained significant attention as an effective approach for the elimination of emerging organic contaminants (EOCs) in water treatment. Metal-organic frameworks (MOFs) and their derivatives are regarded as promising catalysts for activating peroxydisulfate (PDS) and peroxymonosulfate (PMS) due to their tunable and diverse structure and composition. By the rational nanoarchitectured design of MOF-derived nanomaterials, the excellent performance and customized functions can be achieved. However, the intrinsic fine powder form and agglomeration ability of MOF-derived nanomaterials have limited their practical engineering application. Recently, a great deal of effort has been put into shaping MOFs into macroscopic objects without sacrificing the performance. This review presents recent advances in the design and synthetic strategies of MOF-derived nano- and macroarchitectures for PS-AOPs to degrade EOCs. Firstly, the strategies of preparing MOF-derived diverse nanoarchitectures including hierarchically porous, hollow, yolk-shell, and multi-shell structures are comprehensively summarized. Subsequently, the approaches of manufacturing MOF-based macroarchitectures are introduced in detail. Moreover, the PS-AOP application and mechanisms of MOF-derived nano- and macromaterials as catalysts to eliminate EOCs are discussed. Finally, the prospects and challenges of MOF-derived materials in PS-AOPs are discussed. This work will hopefully guide the design and development of MOF-derived porous materials in SR-AOPs.

Diverse Co(II) Coordination Polymers with the Same Mixed Ligands: Evaluation of Chemical Stability and Structural Transformation

Reactions of Co(OAc)2·4H2O, N'N'-bis(3-pyridylmethyl)oxalamide (L) and 4,4'-sulfonyldibenzoic acid (H2SDA) afforded four coordination polymers with the same mixed ligands, {[Co(L)(SDA)(H2O)2]·H2O·CH3OH}n, 1, {[Co(L)0.5(SDA)]·2H2O·0.5L}n, 2, {[Co(L)1.5(SDA)(H2O)]·H2O}n, 3, and {[Co2(L)1.5(SDA)2(H2O)2]·4H2O}n, 4, which have been structurally characterized using single-crystal X-ray crystallography. Complexes 1-4 are 2D layers, revealing topologies of sql, 2,6L1, (4,4)Ia, and 6L12, respectively, and demonstrating that the metal-to-ligand ratio, solvent system, and reaction temperature are important in determining the structural diversity. The immersion of these complexes into various solvents shows that the structural types govern the chemical stabilities of 1-4. Reversible structural transformation is shown for complexes 1 and 2 upon solvent removal and adsorption, while those of 3 and 4 are irreversible.

Spirobifluorene-Based Porous Organic Salts: Their Porous Network Diversification and Construction of Chiral Helical Luminescent Structures

Porous organic salts (POSs) are organic porous materials assembled via charge-assisted hydrogen bonds between strong acids and bases such as sulfonic acids and amines. To diversify the network topology of POSs and extend its functions, this study focused on using 4,4',4'',4'''-(9,9'-spirobi[fluorene]-2,2',7,7'-tetrayl)tetrabenzenesulfonic acid (spiroBPS), which is a tetrasulfonic acid comprising a square planar skeleton. The POS consisting of spiroBPS and triphenylmethylamine (TPMA) (spiroBPS/TPMA) was constructed from the two-fold interpenetration of an orthogonal network with pts topology, which has not been reported in conventional POSs, owing to the shape of the spirobifluorene backbone. Furthermore, combining tris(4-chlorophenyl)methylamine (TPMA-Cl) and tris(4-bromophenyl)methylamine (TPMA-Br), which are bulkier than TPMA owing to the introduction of halogens at the p-position of the phenyl groups with spiroBPS allows us to construct novel POSs (spiroBPS/TPMA-Cl and spiroBPS/TPMA-Br). These POSs were constructed from a chiral helical network with pth topology, which was induced by the steric hindrance between the halogens and the curved fluorene skeleton. Moreover, spiroBPS/TPMA-Cl with pth topology exhibited circularly polarized luminescence (CPL) in the solid state, which has not been reported in hydrogen-bonded organic frameworks (HOFs).

Charge-Assisted Ionic Hydrogen-Bonded Organic Frameworks: Designable and Stabilized Multifunctional Materials

Hydrogen-bonded organic frameworks (HOFs) are a class of crystalline framework materials assembled by hydrogen bonds. HOFs have the advantages of high crystallinity, mild reaction conditions, good solution processability, and reproducibility. Coupled with the reversibility and flexibility of hydrogen bonds, HOFs can be assembled into a wide diversity of crystalline structures. Since the bonding energy of hydrogen bonds is lower than that of ligand and covalent bonds, the framework of HOFs is prone to collapse after desolventisation and the stability is not high, which limits the development and application of HOFs. In recent years, numerous stable and functional HOFs have been developed by π-π stacking, highly interpenetrated networks, charge-assisted, ligand-bond-assisted, molecular weaving, and covalent cross-linking. Charge-assisted ionic HOFs introduce electrostatic attraction into HOFs to improve stability while enriching structural diversity and functionality. In this paper, we review the development, the principles of rational design and assembly of charge-assisted ionic HOFs, and introduces the different building block construction modes of charge-assisted ionic HOFs. Highlight the applications of charge-assisted ionic HOFs in gas adsorption and separation, proton conduction, biological applications, etc., and prospects for the diverse design of charge-assisted ionic HOFs structures and multifunctional applications.

Functionalization of Defective Zr Metal-Organic Frameworks for Water Decontamination: Mechanistic Insight into the Competitive Roles of -NH2 and -SH Sites in Removal of As(III) Species

Direct removal of trivalent arsenic, As(III), arsenite, or H3AsO3, is a great challenge in accessing clean sources of water. Different methodologies and materials were applied in this regard, but among them, direct removal of As(III) species using a metal-organic framework (MOF)-based adsorbent shows a great deal of potential. Although some studies were conducted on As(III) removal using MOFs, studies of functional groups are still quite rare. For this purpose, three novel functionalized defective Zr-MOFs, using UiO-66 [Zr6(OH)4O4(BDC)6, where BDC2- = benzene-1,4-dicarboxylate], were fabricated to investigate the competitive or cooperative roles of the free -NH2 and/or -SH site in the removal of As(III). UiO-66 was functionalized with monocarboxylate linkers, including glycine (Gly, NH2-CH2-COOH), cysteine [Cys, SH(CH2)-NH2(CH)-COOH], and mercaptopropionic acid [Mer, SH-(CH2)2-COOH]. Gly@UiO-66, Cys@UiO-66, and Mer@UiO-66 were applied for the direct removal of As(III) species. Although Cys@UiO-66 is functionalized with both amine and thiol functional groups, Gly@UiO-66 has a higher adsorption capacity (301.4 mg g-1) with respect to As(III), which is among the best reported values. This is due to the fact that (1) the affinity of amine sites in Gly@UiO-66 for As(III) is higher than that of thiol sites in Mer@UiO-66 and (2) Cys@UiO-66 has a very small surface area compared to that of Gly@UiO-66. Mechanistic studies using X-ray photoelectron spectroscopy and vibrational spectroscopy reveal that not only the functionalization and chemical nature of the function but also other parameters such as the protonation-deprotonation mechanisms and chemical state of the function are other critical factors for designing a functional MOF-based adsorbent with high affinity for and maximum capacity with respect to the target analyte.

Utilisation of carbon dioxide and nitrate for urea electrosynthesis with a Cu-based metal-organic framework

It is important and challenging to utilise CO2 and NO3- as a feedstock for electrosynthesis of urea. Herein, we reported a stable 2D metal-organic framework (MOF) Cu-HATNA, possessing planar CuO4 active sites, as an efficient electrocatalyst for coupling CO2 and NO3- into urea, achieving a high yield rate of 1.46 g h-1 gcat-1 with a current density of 44.2 mA cm-1 at -0.6 V vs. RHE. This performance surpasses most of the previously reported catalysts, revealing the great prospects of MOFs in sustainable urea synthesis.

Quest for Multifunctionality: Current Progress in the Characterization of Heterometallic Metal-Organic Frameworks

Metal-organic frameworks (MOFs) are a class of porous, crystalline materials that have been systematically developed for a broad range of applications. Incorporation of two or more metals into a single crystalline phase to generate heterometallic MOFs has been shown to lead to synergistic effects, in which the whole is oftentimes greater than the sum of its parts. Because geometric proximity is typically required for metals to function cooperatively, deciphering and controlling metal distributions in heterometallic MOFs is crucial to establish structure-function relationships. However, determination of short- and long-range metal distributions is nontrivial and requires the use of specialized characterization techniques. Advancements in the characterization of metal distributions and interactions at these length scales is key to rapid advancement and rational design of functional heterometallic MOFs. This perspective summarizes the state-of-the-art in the characterization of heterometallic MOFs, with a focus on techniques that allow metal distributions to be better understood. Using complementary analyses, in conjunction with computational methods, is critical as this field moves toward increasingly complex, multifunctional systems.

Functional groups effect on the toxicity of modified ZIF-90 to Photobacterium phosphoreum

Zeolitic imidazolate framework (ZIF) is of wide interest in biomedical applications due to its extraordinary properties such as high storage capacity, functionality and favorable biocompatibility. However, more comprehensive safety assessments are still essential before ZIF is broadly used in biomedicine. Using the characteristic that aldehyde groups on the surface of ZIF-90 can be modified with other functional groups, a series of ZIF-90s modified with different functional groups (oxime group, carboxyl group, amino group and sulfhydryl group) were synthesized to investigate the effect of functionalization on the toxicity of ZIF-90. ZIF-90 series showed concentration-dependent toxic effects on Photobacterium phosphoreum T3 and the functionalized ZIF-90s are more toxic than pristine ZIF-90, with the ZIF-90 modified with amino group (ZIF-90-NH2) showing the strongest toxicity (IC50 = 23.06 mg/L). Based on the results of the cellular assay and stability exploration, we concluded that corresponding imidazole-ligand release and the property of positively charged are responsible for the elevated toxicity of ZIF-90-NH2. Cell membrane damage, oxidative damage and luminescence damage are the main contributors to the toxic effects of ZIF-90 series. This study explored the effect of surface functionalization on the toxicity of ZIF and proposed mechanistic clues for the safety application of ZIF.

Recent progress of metal-organic framework-based nanozymes with oxidoreductase-like activity

Nanozymes, a class of synthetic nanomaterials possessing enzymatic catalytic properties, exhibit distinct advantages such as exceptional stability and cost-effectiveness. Among them, metal-organic framework (MOF)-based nanozymes have garnered significant attention due to their large specific surface area, tunable pore size and uniform structure. MOFs are porous crystalline materials bridged by inorganic metal ions/clusters and organic ligands, which hold immense potential in the fields of catalysis, sensors and drug carriers. The combination of MOFs with diverse nanomaterials gives rise to various types of MOF-based nanozyme, encompassing original MOFs, MOF-based nanozymes with chemical modifications, MOF-based composites and MOF derivatives. It is worth mentioning that the metal ions and organic ligands in MOFs are perfectly suited for designing oxidoreductase-like nanozymes. In this review, we intend to provide an overview of recent trends and progress in MOF-based nanozymes with oxidoreductase-like activity. Furthermore, the current obstacles and prospective outlook of MOF-based nanozymes are proposed and briefly discussed. This comprehensive analysis aims to facilitate progress in the development of novel MOF-based nanozymes with oxidoreductase-like activity while serving as a valuable reference for scientists engaged in related disciplines.

Functionalization of Defective Zr-MOFs for Water Decontamination: Mechanistic Insight into the Competitive Roles of -NH2 and -SH Sites in the Removal of Hg(II) Ions

Functional metal-organic frameworks (MOFs), especially those based on sulfur and nitrogen atoms, were frequently applied for the removal of Hg(II) ions. However, a systematic study on the cooperative or competitive roles of -SH and -NH2 functions in the presence of secondary mechanisms (proton transfer and redox) is still rare. In this work, the UiO-66 framework (Zr6(OH)4O4(BDC)6, BDC2- = benzene-1,4-dicarboxylate) was decorated with functional monocarboxylate linkers including glycine (Gly), mercaptopropionic acid (Mer), and cysteine (Cys). Due to the molecular similarity of these functional linkers, the coordination affinity between the amine and thiol sites with Hg(II) ions can be compared, and the effect of proton transfer and redox mechanisms on the possible thiol···Hg(II) and amine···Hg(II) interactions can be investigated. The results show that the Cys@UiO-66 framework can adsorb 1288 mg g-1 of Hg(II), while Mer@UiO-66 and Gly@UiO-66 can adsorb 593 and 313 mg g-1 at pH = 7 and 500 ppm, respectively. This is due to the facts that both the amine and the thiol functions of the Cys@UiO-66 framework show synergism in Hg(II) removal, and the secondary mechanisms reduce the affinity of thiol in Mer@UiO-66 and amine in Gly@UiO-66 frameworks in the removal process of Hg(II) ions. Free -SH sites in Mer@UiO-66 undergo a redox convert to -SO3H groups, and free protonated -NH2 sites in Gly@UiO-66 do not fully deprotonate during Hg(II) removal. Yet, in the case of Cys@UiO-66, free protonated -NH2 sites are fully deprotonated, and free SH sites did not convert to -SO3H groups during Hg(II) removal. These observations show that the redox and proton transfer mechanisms can negatively affect the adsorption capacity of functional MOFs containing free -SH and -NH2 groups. So, not only the functionalization but also control over secondary mechanisms in the removal process are necessary parameters to improve the affinity between functional MOFs and Hg(II) ions.

Synthesis and Oxygen Evolution Reaction Application of a Co-Cd Based Bimetallic Metal-Organic Framework

In the realm of renewable energy technologies, the development of efficient and durable electrocatalysts is paramount, especially for applications like electrochemical water splitting. This research focuses on synthesizing a novel bimetallic metal-organic framework (BMMOF11) using earth-abundant elements, cobalt (Co) and cadmium (Cd). BMMOF11 showcases a distinctive structure with distorted octahedral chains of CoO and CdO, linked by benzene tricarboxylic acid (BTC). Our study primarily investigates the electrocatalytic efficiency of BMMOF11, particularly in water oxidation reactions. For practical analysis, BMMOF11 was anchored onto nickel foam, forming BMMOF11/NF, to evaluate its electrocatalytic properties. Electrochemical testing revealed that BMMOF11/NF begins water oxidation at an onset potential of 1.62 V versus RHE, demonstrating high activity with a lower overpotential of 0.4 V to achieve a current density of 10 mA/cm2 . Moreover, BMMOF11/NF maintained stable water splitting performance, sustaining a current density of approximately 70 mA/cm2 under a voltage of 1.9 V relative to RHE. These findings indicate that BMMOF11/NF is a promising candidate for large-scale electrochemical water splitting, offering a blend of high activity and stability.

Construction of Porphyrin-Based Bimetallic Nanomaterials with Photocatalytic Properties

The efficient synthesis of nanosheets containing two metal ions is currently a formidable challenge. Here, we attempted to dope lanthanide-based bimetals into porphyrin-based metal-organic skeleton materials (MOFs) by microwave-assisted heating. The results of the EDX, ICP, and XPS tests show that we have successfully synthesized porphyrin-based lanthanide bimetallic nanosheets (Tb-Eu-TCPP) using a household microwave oven. In addition, it is tested and experimentally evident that these nanosheets have a thinner thickness, a larger BET surface area, and higher photogenerated carrier separation efficiency than bulk porphyrin-based bimetallic materials, thus exhibiting enhanced photocatalytic activity and n-type semiconductor properties. Furthermore, the prepared Tb-Eu-TCPP nanomaterials are more efficient in generating single-linear state oxygen under visible light irradiation compared to pristine monometallic nanosheets due to the generation of bimetallic nodes. The significant increase in catalytic activity is attributed to the improved separation and transfer efficiency of photogenerated carriers. This study not only deepens our understanding of lanthanide bimetallic nanosheet materials but also introduces an innovative approach to improve the photocatalytic performance of MOFs.

MOF-Based Photocatalytic Membrane for Water Purification: A Review

Photocatalytic membranes can effectively integrate membrane separation and photocatalytic degradation processes to provide an eco-friendly solution for efficient water purification. It is of great significance to develop highly efficient photocatalytic membranes driven by visible light to ensure the long-term stability of membrane separation systems and the maximum utilization of solar energy. Metal-organic framework (MOF) is an emerging photocatalyst with a well-defined structure and tunable chemical properties, showing a broad application prospect in the construction of high-performance photocatalytic membranes. Herein, this work provides a comprehensive review of recent advancements in MOF-based photocatalytic membranes. Initially, this work outlines the main tailoring strategies that facilitate the enhancement of the photocatalytic activity of MOF-based photocatalysts. Next, this work introduces commonly used methods for fabricating MOF-based photocatalytic membranes. Subsequently, this work discusses the application and mechanisms of MOF-based photocatalytic membranes toward organic pollutant degradation, metal ion removal, and membrane fouling mitigation. Finally, challenges in developing MOF-based photocatalytic membranes and their practical applications are presented, while also pointing out future research directions toward overcoming these existing limitations.

Tuning the Cerium-Based Metal-Organic Framework Formation by Template Effect and Precursor Selection

The novel metal-organic framework [(CH3)2NH2]2[Ce2(bdc)4(DMF)2]·2H2O (Ce-MOF, H2bdc-terephthalic acid, DMF-N,N-dimethylformamide) was synthesized by a simple solvothermal method. Ce-MOF has 3D connectivity of bcu type with a dinuclear fragment connected with eight neighbors, while three types of guest species are residing in its pores: water, DMF, and dimethylammonium cations. Dimethylamine was demonstrated to have a decisive templating effect on the formation of Ce-MOF, as its deliberate addition to the solvothermal reaction allows the reproducible synthesis of the new framework. Otherwise, the previously reported MOF Ce5(bdc)7.5(DMF)4 (Ce5) or its composite with nano-CeO2 (CeO2@Ce5) was obtained. Various Ce carboxylate precursors and synthetic conditions were explored to evidence the major stability of Ce-MOF and Ce5 within the Ce carboxylate-H2bdc-DMF system. The choice of precursor impacts the surface area of Ce-MOF and thus its reactivity in an oxidative atmosphere. The in situ PXRD and TG-DTA-MS study of Ce-MOF in a nonoxidative atmosphere demonstrates that it eliminates H2O and DMF along with (CH3)2NH guest species in two distinct stages at 70 and 250 °C, respectively, yielding [Ce2(bdc)3(H2bdc)]. The H2bdc molecule is removed at 350 °C with the formation of novel modification of Ce2(bdc)3, which is stable at least up to 450 °C. According to the total X-ray scattering study with pair distribution function analysis, the most pronounced local structure transformation occurs upon departure of DMF and (CH3)2NH guest species, which is in line with the in situ PXRD experiment. In an oxidative atmosphere, Ce-MOF undergoes combustion to CeO2 at a temperature as low as 390 °C. MOF-derived CeO2 from Ce-MOF, Ce5, and CeO2@Ce5 exhibits catalytic activity in the CO oxidation reaction.

Target Design of Multinary Metal-Organic Frameworks for Near-Infrared Imaging and Chemodynamic Therapy

Imaging-guided chemodynamic therapy is widely considered a promising modality for personalized and precision cancer treatment. Combining both imaging and chemodynamic functions in one system conventionally relies on the hybrid materials approach. However, the heterogeneous, ill-defined, and dissociative/disintegrative nature of the composites tends to complicate their action proceedings in biological environments and thus makes the treatment imprecise and ineffective. Herein, a strategy to employ two kinds of inorganic units with different functions─reactive oxygen species generation and characteristic emission─has achieved two single-crystalline metal-organic frameworks (MOFs), demonstrating the competency of reticular chemistry in creating multifunctional materials with atomic precision. The multinary MOFs could not only catalyze the transformation from H2O2 to hydroxyl radicals by utilizing the redox-active Cu-based units but also emit characteristic tissue-penetrating near-infrared luminescence brought by the Yb4 clusters in the scaffolds. Dual functions of MOF nanoparticles are further evidenced by pronounced cell imaging signals, elevated intracellular reactive oxygen species levels, significant cell apoptosis, and reduced cell viabilities when they are taken up by the HeLa cells. In vivo NIR imaging is demonstrated after the MOF nanoparticles are further functionalized. The independent yet interconnected modules in the intact MOFs could operate concurrently at the same cellular site, achieving a high spatiotemporal consistency. Overall, our work suggests a new method to effectively accommodate both imaging and therapy functions in one well-defined material for precise treatment.

Flexible nanofibrous membranes of dual metallic metal-organic framework with enhanced Lewis basic sites and high loading mass for efficient CO2 capture

Excessive CO2 emissions and the resultant global warming present significant environmental challenges, posing threats to human health and public safety. Metal-organic frameworks (MOFs), known for their high specific area and large porosity, hold the promise for CO2 capture. However, a major obstacle is the low loading mass of MOFs and the limited interface affinity and compatibility between MOFs and substrates. In this study, we present an electrospinning-assisted in-situ synthesis dual metallic framework strategy for preparing flexible Zn/Co-ZIF nanofibrous membranes (NFMs). This method achieves the high loading mass of MOFs and introduces abundant Lewis basic sites, thereby enhancing the CO2 adsorption. The dual metallic Zn/Co-ZIF NFMs exhibit remarkable features, including high MOF loading mass (70.23 wt%), high specific surface area (379.63 m2g-1), large porosity (92.34 %), high CO2 adsorption capacity (4.43 mmol/g), high CO2/N2 adsorption selectivity (37), and high CO2/CH4 adsorption selectivity (31). Moreover, the dual metallic Zn/Co-ZIF NFMs demonstrate robust structural stability and durability attributed to the excellent interface affinity between MOFs and NFMs, retaining 96.56 % of their initial capacity after 10 adsorption-desorption cycles. This work presents a prospective direction for developing flexible dual metallic MOF NFMs for the efficient capture of CO2.

Metal-organic frameworks (MOFs) for energy production and gaseous fuel and electrochemical energy storage applications

The increasing energy demands in society and industrial sectors have inspired the search for alternative energy sources that are renewable and sustainable, also driving the development of clean energy storage and delivery systems. Various solid-state materials (e.g., oxides, sulphides, polymer and conductive nanomaterials, activated carbon and their composites) have been developed for energy production (water splitting-H2 production), gaseous fuel (H2 and CH4) storage and electrochemical energy storage (batteries and supercapacitors) applications. Nevertheless, the low surface area, pore volume and conductivity, and poor physical and chemical stability of the reported materials have resulted in higher requirements and challenges in the development of energy production and energy storage technologies. Thus, to overcome these issues, the development of metal-organic frameworks (MOFs) has attracted significant attention. MOFs are a class of porous materials with extremely high porosity and surface area, structural diversity, multifunctionality, and chemical and structural stability, and thus they can be used in a wide range of applications. In the present review, we precisely discuss the interesting properties of MOFs and the various methodologies for their synthesis, and also the future dependence on the valorization of solid waste for the recovery of metals and organic ligands for the synthesis of new classes of MOFs. Subsequently, the utilization of these interesting characteristics for energy production (water splitting), storage of gaseous fuels (H2 and CH4), and electrochemical storage (batteries and supercapacitors) applications are described. However, although MOFs are efficient materials with versatile uses, they still have many challenges, limiting their practical applications. Therefore, finally, we highlight the challenges associated with MOFs and show the way forward in overcoming them for the development of these highly porous materials with large-scale practical utility.

Prediction of the capture and utilization of atmospheric acidic gases by azo-based square-pillared fluorinated MOFs

More than the permissible limit of acidic gases like CO2, SO2, and NO2 in the atmosphere are responsible for the formation of acid rain, the greenhouse effect and many other undesirable environmental hazards. So, the capture and utilization of these gases are essential for mankind. Herein, we proposed an azo-based square pillared MOF, [Ni(MF5)(1,2-bis(4-pyridy)diazene)2]n, with the CUS metal site, i.e. M = Al/Fe, for the selective capture and conversion of acidic gas molecules into commodity chemicals such as cyclic carbonate, sulphite and nitrite. With the aid of Density Functional Theory (DFT), [Ni(MF5)(1,2-bis(4-pyridy)diazene)2]n has been optimized, and the specific force field is derived via guest-host interaction. The Grand Canonical Monte Carlo (GCMC) simulation has been used to explore the guest-host interactions over a wide range of pressures, and their respective stability under pre-humidification is evaluated. The adsorption prediction reveals that MFFIVE-Ni-apy have a higher adsorptive capacity (37.1 mmol g-1), and especially ALFFIVE-Ni-apy possesses a higher affinity towards guest molecules (CO2, SO2) rather than FEFFIVE-Ni-apy. Additionally, the adsorption of gases in the presence of humidity reveals that ALFFIVE-Ni-apy has an optimal adsorption capacity for all investigated acidic gases even at 38.5 RH%. The absorbed acidic gases on MFFIVE-Ni-apy were used for the theoretical investigations on cycloaddition with the aid of DFT as an application perspective of the toxic gases instead of expelling into atmosphere. The Climbing Image Nudged Elastic Band (CI-NEB) approach was used to discover the transition state in this scenario, in which the cycloaddition of adsorbed CO2, SO2, and NO2 gases with epoxides leads to the formation of cyclic carbonates, sulphites, and nitrates, respectively.

Postsynthetic Modification of the Nonanuclear Node in a Zirconium Metal-Organic Framework for Photocatalytic Oxidation of Hydrocarbons

Heterogeneous catalysis plays an indispensable role in chemical production and energy conversion. Incorporation of transition metals into metal oxides and zeolites is a common strategy to fine-tune the activity and selectivity of the resulting solid catalysts, as either the active center or promotor. Studying the underlying mechanism is however challenging. Decorating the metal-oxo clusters with transition metals in metal-organic frameworks (MOFs) via postsynthetic modification offers a rational approach to construct well-defined structural models for better understanding of the reaction mechanism. Therefore, it is important to expand the materials scope beyond the currently widely studied zirconium MOFs consisting of Zr6 nodes. In this work, we report the design and synthesis of a new (4,12)-connected Zr-MOF with ith topology that consists of rare Zr9 nodes. FeIII was further incorporated onto the Zr9 nodes of the framework, and the resulting MOF material exhibits significantly enhanced activity and selectivity toward the photocatalytic oxidation of toluene. This work demonstrates a delicate ligand design strategy to control the nuclearity of Zr-oxo clusters, which further dictates the number and binding sites of transition metals and the overall photocatalytic activity toward C-H activation. Our work paves the way for future exploration of the structure-activity study of catalysts using MOFs as the model system.

Cyclodextrin-based metal-organic framework materials: Classifications, synthesis strategies and applications in variegated delivery systems

Metal-organic frameworks (MOFs) are coordination compounds that possess an adjustable structure and controllable function. Despite their wide applications in various industries, the use of MOFs in the fields of food and biomedicine is limited mainly due to their potential biological toxicity. Researchers have thus focused on developing biocompatible MOFs to address this issue. Among them, cyclodextrin-based metal-organic frameworks (CD-MOFs) have emerged as a promising alternative. CD-MOFs are novel MOFs synthesized using naturally carbohydrate cyclodextrin and alkali metal cations, and possess renewable, non-toxic, and edible characteristics. Due to their high specific surface area, controllable porosity, great biocompatibility, CD-MOFs have been widely used in various delivery systems, such as encapsulation of nutraceuticals, flavors, and antibacterial agents. Although the field of CD-MOF materials is still in its early stages, they provide a promising direction for the development of MOF materials in the delivery field. This review describes classification and structural characteristics, followed by an introduction to formation mechanism and commonly used synthetic methods for CD-MOFs. Additionally, we discuss the status of the application of various delivery systems based on CD-MOFs. Finally, we address the challenges and prospects of CD-MOF materials, with the aim of providing new insights and ideas for their future development.

Porous Ionic Liquids Go Green

This Perspective points toward pathways to prepare porous ionic liquids using easily accessible materials, aiming for reduced environmental impact. We demonstrate that suspensions of porous solids are stable in eutectic mixtures, underscoring their potential for the preparation of porous ionic liquids. Porous ionic liquids retain the wide electrochemical window observed in their precursor pure ionic liquids, rendering them well-suited for green electrochemical reactions, particularly those involving gases whose solubility is enhanced in the porous suspensions. Moreover, their capacity as gas-rich media points to sustainable biomedical and pharmaceutical applications, provided nontoxic, biocompatible ionic liquids and porous solids are utilized.

Boosting the catalysis of cesium phosphomolybdate encapsulated in hierarchical porous UiO-66 by microenvironment modulation for epoxidation of alkenes

The chemical microenvironment of polyoxometalates (POMs) encapsulated in metal-organic frameworks (MOFs) presents a significant influence on their catalytic performance, which can be easily regulated by the linker functional group alteration or metal substitution in MOFs. Herein, a series of cesium phosphomolybdate (CsPM) encapsulated in hierarchical porous UiO-66-X composites (CsPM@HP-UiO-66-X, X = H, 2CH3, or 2OH, where X represents the alterable group grafted onto the linker benzene ring) were successfully synthesized through a one pot modulated solvothermal method. The catalytic performances of the obtained materials were explored in alkene epoxidation reaction with tert-butyl hydroperoxide (t-BuOOH). CsPM@HP-UiO-66-2CH3 showed relatively high catalytic activity, stability, and epoxidation selectivity in cyclooctene epoxidation among the CsPM@HP-UiO-66-X composites. Moreover, CsPM@HP-UiO-66-2CH3 was effective in the epoxidation of numerous alkenes, especially cyclic alkenes. The superior catalytic activity of CsPM@HP-UiO-66-2CH3 is mainly attributed to the modulation of the microenvironment surrounding CsPM active sites by introducing a hydrophobic methyl group. Meanwhile, the size-matched effect, the introduction of cesium cations, and the strong metal-support interactions (SMSIs) between CsPM and HP-UiO-66-2CH3 play a crucial role in the stability of CsPM@HP-UiO-66-2CH3.

Taming Multiscale Structural Complexity in Porous Skeletons: From Open Framework Materials to Micro/Nanoscaffold Architectures

Recent developments in the design and synthesis of more and more sophisticated organic building blocks with controlled structures and physical properties, combined with the emergence of novel assembly modes and nanofabrication methods, make it possible to tailor unprecedented structurally complex porous systems with precise multiscale control over their architectures and functions. By tuning their porosity from the nanoscale to microscale, a wide range of functional materials can be assembled, including open frameworks and micro/nanoscaffold architectures. During the last two decades, significant progress is made on the generation and optimization of advanced porous systems, resulting in high-performance multifunctional scaffold materials and novel device configurations. In this perspective, a critical analysis is provided of the most effective methods for imparting controlled physical and chemical properties to multifunctional porous skeletons. The future research directions that underscore the role of skeleton structures with varying physical dimensions, from molecular-level open frameworks (<10 nm) to supramolecular scaffolds (10-100 nm) and micro/nano scaffolds (>100 nm), are discussed. The limitations, challenges, and opportunities for potential applications of these multifunctional and multidimensional material systems are also evaluated in particular by addressing the greatest challenges that the society has to face.

Opportunities and Challenges of Metal-Organic Framework Micro/Nano Reactors for Cascade Reactions

Building bridges among different types of catalysts to construct cascades is a highly worthwhile pursuit, such as chemo-, bio-, and chemo-bio cascade reactions. Cascade reactions can improve the reaction efficiency and selectivity while reducing steps of separation and purification, thereby promoting the development of "green chemistry". However, compatibility issues in cascade reactions pose significant constraints on the development of this field, particularly concerning the compatibility of diverse catalyst types, reaction conditions, and reaction rates. Metal-organic framework micro/nano reactors (MOF-MNRs) are porous crystalline materials formed by the self-assembly coordination of metal sites and organic ligands, possessing a periodic network structure. Due to the uniform pore size with the capability of controlling selective transfer of substances as well as protecting active substances and the organic-inorganic parts providing reactive microenvironment, MOF-MNRs have attracted significant attention in cascade reactions in recent years. In this Perspective, we first discuss how to address compatibility issues in cascade reactions using MOF-MNRs, including structural design and synthetic strategies. Then we summarize the research progress on MOF-MNRs in various cascade reactions. Finally, we analyze the challenges facing MOF-MNRs and potential breakthrough directions and opportunities for the future.

Recent Advances in Multifunctional Reticular Framework Nanoparticles: A Paradigm Shift in Materials Science Road to a Structured Future

Porous organic frameworks (POFs) have become a highly sought-after research domain that offers a promising avenue for developing cutting-edge nanostructured materials, both in their pristine state and when subjected to various chemical and structural modifications. Metal-organic frameworks, covalent organic frameworks, and hydrogen-bonded organic frameworks are examples of these emerging materials that have gained significant attention due to their unique properties, such as high crystallinity, intrinsic porosity, unique structural regularity, diverse functionality, design flexibility, and outstanding stability. This review provides an overview of the state-of-the-art research on base-stable POFs, emphasizing the distinct pros and cons of reticular framework nanoparticles compared to other types of nanocluster materials. Thereafter, the review highlights the unique opportunity to produce multifunctional tailoring nanoparticles to meet specific application requirements. It is recommended that this potential for creating customized nanoparticles should be the driving force behind future synthesis efforts to tap the full potential of this multifaceted material category.

A 3D tetrathiafulvalene-based metal-organic framework with intramolecular charge transfer for efficient near-infrared photothermal conversion

The selection of metal centers can endow donor-metal-accepter (D-M-A) type MOFs with progressive framework dimensions. 3D Cd-based MOFs with intramolecular charge transfer caused by D-M-A exhibit a satisfactory photothermal conversion efficiency of 35.7%, with the temperature rapidly rising from 25 °C to 201 °C in 7 s under 808 nm laser irradiation.

Bioinspired microenvironment modulation of metal-organic framework-based catalysts for selective methane oxidation

Inspiration from natural enzymes enabling creationary catalyst design is appealing yet remains extremely challenging for selective methane (CH4) oxidation. This study presents the construction of a biomimetic catalyst platform for CH4 oxidation, which is constructed by incorporating Fe-porphyrin into a robust metal-organic framework, UiO-66, furnished with saturated monocarboxylic fatty acid bearing different long alkyl chains. The catalysts demonstrate the high efficiency in the CH4 to methanol (CH3OH) conversion at 50 °C. Moreover, the selectivity to CH3OH can be effectively regulated and promoted through a fine-tuned microenvironment by hydrophobic modification around the Fe-porphyrin. The long-chain fatty acids anchored on the Zr-oxo cluster of UiO-66 can not only tune the electronic state of the Fe sites to improve CH4 adsorption, but also restrict the amount of H2O2 around the Fe sites to reduce the overoxidation. This behavior resembles the microenvironment regulation in methane monooxygenase, resulting in high CH3OH selectivity.

The screening of lipase inhibitors based on the metal-organic framework Zeolitic Imidazolate Framework-8-immobilized enzyme microreactor

An online capillary electrophoresis method based-lipase immobilized enzyme microreactor was developed for lipase kinetic study and inhibitor screening from compounds from natural products. Zeolitic Imidazolate Framework-8 (ZIF-8) has the advantages of large pore size, mild synthesis conditions and good biocompatibility. Lipase was immobilized on the inner wall of capillary with the help of the metal-organic framework ZIF-8. The results of electron microscopy showed that lipase could be aggregated and fixed on the inner wall of capillary by ZIF-8. After the experimental conditions including electrophoretic separation and enzymatic reaction were optimized, the baseline separation of substrate p-nitrophenyl acetate (pNPA) and product p-nitrophenol (pNP) was achieved within 3 min. The immobilized enzyme microreactor showed good repeatability and stability, and the determined Michaelis-Menten constant (Km) of lipase was 2.75 mM, which was lower than the kinetic constant determined in off-line reaction, indicating that the immobilized enzyme had a high affinity with the substrate. In addition, the IC50 value of the positive control compound orlistat on lipase inhibition was 7.26 nM, which was consistent with the literature. Then the inhibitory activity of 10 compounds from natural products on lipase was evaluated by the ZIF-8-IMER. Among them, 7 compounds including baicalein, luteolin, epicatechin gallic acid, and chlorogenic acid, had a certain inhibitory effect on lipase. The molecular docking technology proved the interaction between the enzyme and the screened inhibitor, which provides a new method for the screening of lipase inhibitors.

Dual-Emitting Mixed-Lanthanide Metal-Organic Framework for Ratiometric and Quantitative Visual Detection of 2,6-Pyridine Dicarboxylic Acid

The detection of the major biomarker of Bacillus anthracis, 2,6-dipicolinic acid (DPA), has attracted great interest in recent years. In this work, mixed-lanthanide metal-organic frameworks (M'LnMOFs), TbxEu1-x-cppa (cppa = 5-(5-carboxypyridin-3-yl)isophthalic acid), with different Tb/Eu ratios, were solvothermally synthesized. The results reveal that ratiometric fluorescent probe [Tb0.533Eu0.467-(Hcppa)1.5(H2O)(DMF)]·3H2O is water and acid-base stable and exhibits excellent sensitivity (LOD = 2.286 μM), high selectivity, and fast response (<2 min) for the detection of DPA. Due to the blocked energy transfer from Tb3+ to Eu3+ and the inner filter effect upon the addition of DPA, the fluorescent probe shows a distinct color change from orange-red to green. Furthermore, the visual detection of DPA was realized by identifying the RGB values of MOF-based agarose hydrogel films via a smartphone, highlighting the practical application of the fluorescent probe for DPA detection under aqueous solution conditions.

Linker Engineering of Sandwich-Structured Metal-Organic Framework Composites for Optimized Photocatalytic H2 Production

While the microenvironment around catalytic sites is recognized to be crucial in thermocatalysis, its roles in photocatalysis remain subtle. In this work, a series of sandwich-structured metal-organic framework (MOF) composites, UiO-66-NH2 @Pt@UiO-66-X (X means functional groups), is rationally constructed for visible-light photocatalytic H2 production. By varying the ─X groups of the UiO-66-X shell, the microenvironment of the Pt sites and photosensitive UiO-66-NH2 core can be simultaneously modulated. Significantly, the MOF composites with identical light absorption and Pt loading present distinctly different photocatalytic H2 production rates, following the ─X group sequence of ─H > ─Br > ─NA (naphthalene) > ─OCH3  > ─Cl > ─NO2 . UiO-66-NH2 @Pt@UiO-66-H demonstrates H2 production rate up to 2708.2 µmol g-1  h-1 , ≈222 times that of UiO-66-NH2 @Pt@UiO-66-NO2 . Mechanism investigations suggest that the variation of the ─X group can balance the charge separation of the UiO-66-NH2 core and the proton reduction ability of Pt, leading to an optimal activity of UiO-66-NH2 @Pt@UiO-66-H at the equilibrium point.

A simple and portable vacuum assisted headspace solid phase microextraction device coupled to gas chromatography based on covalent organic framework/metal organic framework hybrid for simultaneous analysis of volatile and semi-volatile compounds in soil

Various microextraction methods have demonstrated a positive effect when assisted by vacuum. However, working with such systems is often laborious, they often require expensive and non-portable vacuum pumps, and may even suck off some sample vapor or solid particles during the evacuation process. To address these issues, a simple, and affordable vacuum-assisted headspace solid-phase microextraction (HS-SPME) device was developed in this study. The device, named In Syringe Vacuum-assisted HS-SPME (ISV-HS-SPME), utilizes an adjustable 40 mL glass syringe as a vacuum provider and sampling vessel. A new fiber coating, made from a hybrid of covalent triazine-based frameworks and metal-organic frameworks (COF/MOF), was prepared and characterized by Fourier transform infrared spectrometry, field emission scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, thermogravimetric analysis, and Brunauer-Emmett-Teller techniques for use in the ISV-HS-SPME. By optimizing parameters such as extraction temperature, extraction time, desorption temperature, desorption time, and, humidity using a simplex method, the ISV system was found to increase the extraction efficiency of polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene, and xylenes (BTEX) in solid samples by up to 175%. The determinations were followed by GC-FID measurements. Compared to three commercially available fibers, the ISV-HS-SPME device with the COF/MOF (2DTP/MIL-101-Cr) fiber exhibited significantly higher peak areas for PAHs and BTEX. The linear dynamic ranges for BTEX and PAHs were 7.1-9000 ng g-1 and 0.23-9000 ng g-1, respectively, with limits of detection ranging from 2.1-5 ng g-1 for BTEX and 0.07-1.6 ng g-1 for PAHs. The relative standard deviation of the method was 2.6-7.8% for BTEX and 1.6-6.7% for PAHs. The ISV-HS-SPME was successfully used to simultaneously determine PAHs and BTEX in polluted soil samples with recoveries ranging from 80.4 to 108%.