Design of Multivariate Biological Metal-Organic Frameworks: Toward Mimicking Active Sites of Enzymes

Mimicking enzymatic processes carried out by natural enzymes, which are highly efficient biocatalysts with key roles in living organisms, attracts much interest but constitutes a synthetic challenge. Biological metal-organic frameworks (bioMOFs) are potential candidates to be enzyme catalysis mimics, as they offer the possibility to combine biometals and biomolecules into open-framework porous structures capable of simulating the catalytic pockets of enzymes. In this work, we first study the catalase activity of a previously reported bioMOF, derived from the amino acid L-serine, with formula {CaIICuII6[(S,S)-serimox]3(OH)2(H2O)} · 39H2O (1) (serimox = bis[(S)-serine]oxalyl diamide), which is indeed capable to mimic catalase enzymes, in charge of preventing cell oxidative damage by decomposing, efficiently, hydrogen peroxide to water and oxygen (2H2O2 → 2 H2O + O2). With these results in hand, we then prepared a new multivariate bioMOF (MTV-bioMOF) that combines two different types of bioligands derived from L-serine and L-histidine amino acids with formula CaIICuII6[(S,S)-serimox]2[(S,S)-hismox]1(OH)2(H2O)}·27H2O (2) (hismox = bis[(S)-histidine]oxalyl diamide ligand). MTV-bioMOF 2 outperforms 1 degrading hydrogen peroxide, confirming the importance of the amino acid residue from the histidine amino acid acting as a nucleophile in the catalase degradation mechanism. Despite displaying a more modest catalytic behavior than other reported MOF composites, in which the catalase enzyme is immobilized inside the MOF, this work represents the first example of a MOF in which an attempt is made to replicate the active center of the catalase enzyme with its constituent elements and is capable of moderate catalytic activity.

A sulfonate ligand-defected Zr-based metal-organic framework for the enhanced selective removal of anionic dyes

In this work, we introduce a novel defective analogue of the representative 6-connected zirconium-based metal-organic framework (MOF-808), by employing 5-sulfoisophthalic acid monosodium salt (H2BTC-SO3Na) as a defect inducer via a mixed-linker approach. The structural integrity and different physicochemical properties were investigated by various characterization techniques, including powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and nitrogen physisorption at 77 K. Additionally, proton nuclear magnetic resonance (1H-NMR), energy-dispersive X-ray (EDX), and inductively coupled plasma optical emission spectroscopy (ICP-OES) were employed to confirm the presence of 6.9 mol% of the 5-sulfoisophthalate ligand within the highly crystalline MOF-808 structure. The defective material exhibited significant enhancements in the removal efficiency of various organic dyes, including approximately 64% and 77% for quinoline yellow and sunset yellow, and 56% and 13% for rhodamine B and malachite green, compared to its pristine counterpart. Importantly, the defective MOF-808 showed a remarkable selectivity toward anionic species in binary-component dyes comprising both anionic and cationic dyes.

Amyloid detection in neurodegenerative diseases using MOFs

Neurodegenerative diseases (amyloid diseases such as Alzheimer's and Parkinson's), stemming from protein misfolding and aggregation, encompass a spectrum of disorders with severe systemic implications. Timely detection is pivotal in managing these diseases owing to their significant impact on organ function and high mortality rates. The diverse array of amyloid disorders, spanning localized and systemic manifestations, underscores the complexity of these conditions and highlights the need for advanced detection methods. Traditional approaches have focused on identifying biomarkers using imaging techniques (PET and MRI) or invasive procedures. However, recent efforts have focused on the use of metal-organic frameworks (MOFs), a versatile class of materials known for their unique properties, in revolutionizing amyloid disease detection. The high porosity, customizable structures, and biocompatibility of MOFs enable their integration with biomolecules, laying the groundwork for highly sensitive and specific biosensors. These sensors have been employed using electrochemical and photophysical techniques that target amyloid species under neurodegenerative conditions. The adaptability of MOFs allows for the precise detection and quantification of amyloid proteins, offering potential advancements in early diagnosis and disease management. This review article delves into how MOFs contribute to detecting amyloid diseases by categorizing their uses based on different sensing methods, such as electrochemical (EC), electrochemiluminescence (ECL), fluorescence, Förster resonance energy transfer (FRET), up-conversion luminescence resonance energy transfer (ULRET), and photoelectrochemical (PEC) sensing. The drawbacks of MOF biosensors and the challenges encountered in the field are also briefly explored from our perspective.

Bio-Inspired Subnanofluidics: Advanced Fabrication and Functionalization

Biological ion channels can realize high-speed and high-selective ion transport through the protein filter with the sub-1-nanometer channel. Inspired by biological ion channels, various kinds of artificial subnanopores, subnanochannels, and subnanoslits with improved ion selectivity and permeability are recently developed for efficient separation, energy conversion, and biosensing. This review article discusses the advanced fabrication and functionalization methods for constructing subnanofluidic pores, channels, tubes, and slits, which have shown great potential for various applications. Novel fabrication methods for producing subnanofluidics, including top-down techniques such as electron beam etching, ion irradiation, and electrochemical etching, as well as bottom-up approaches starting from advanced microporous frameworks, microporous polymers, lipid bilayer embedded subnanochannels, and stacked 2D materials are well summarized. Meanwhile, the functionalization methods of subnanochannels are discussed based on the introduction of functional groups, which are classified into direct synthesis, covalent bond modifications, and functional molecule fillings. These methods have enabled the construction of subnanochannels with precise control of structure, size, and functionality. The current progress, challenges, and future directions in the field of subnanofluidic are also discussed.

A Green Environmental Protection Photocatalytic Molecular Reactor for Aerobic Oxidation of Sulfide to Sulfoxide

The design and synthesis of metal-organic frameworks (MOFs) as photocatalytic molecular reactors for varied reactions have drawn great attention. In this work, we designed a novel photoactive perylenediimides-based (PDI) carboxylate ligand N,N'-di(3',3",5',5"-tetrakis(4-carboxyphenyl))-1,2,6,7-tetrachloroperylene-3,4,9,10-tetracarboxylic acid diimide (Cl-PDI-TA) and use it to successfully synthesize a novel Zr(IV)-based MOF 1 constructed from [Zr6 O8 (H2 O)8 ]8+ clusters bridged by Cl-PDI-TA ligands. Structural analysis revealed that Zr-MOF 1 manifests a 3D framework with (4,8)-connected csq topology and possesses triangular channels of ~17 Å and mesoporous hexagonal channels of ~26 Å along c-axis. Moreover, the synthesized Zr-MOF 1 exhibits visible-light absorption and efficient photoinduced free radical generation property, making it a promising photocatalytic molecular reactor. When Zr-MOF 1 was used as a photocatalyst for the aerobic oxidation of sulfides under irradiation of visible light, it could afford the corresponding sulfoxides with high yield and selectivity. Experimental results demonstrated that the substrate sulfides could be fixed in the pores of 1 and directly transformed to the products sulfoxides in the solid state. Furthermore, the mechanism for the photocatalytic transformation was also investigated and the results revealed that the singlet oxygen (1 O2 ) and superoxide radical (O2 ⋅- ) generated by the energy transfer and electron transfer from the photoexcited Zr-MOF to oxidants were the main active species for the catalytic reactions. This work offers a perceptive comprehension of the mechanism in PDI-based MOFs for further study on photocatalytic reactions.

Colorimetric immunoassay of carcinoembryonic antigen based on the glucose oxidase/MnO2 nanosheet cascade reaction with self-supplying oxygen

The detection of carcinoembryonic antigen (CEA) has profound implications in cancer diagnostics and therapeutic monitoring. In this work, we developed a colorimetric immunoassay for the detection of CEA. This assay involves the utilization of zinc(II)-based coordination polymers (ZnCPs) as a host for integrating glucose oxidase (GOx) and anti-carcinoembryonic antigen antibody (anti-CEA), which results in the formation of a detection antibody (anti-CEA/GOx@ZnCPs). The adaptable inclusion properties of ZnCPs enable the preservation of the original catalytic behavior of GOx and antigen capture ability of anti-CEA. Consequently, the anti-CEA/GOx@ZnCPs can act as a detection antibody to facilitate the development of an immunoassay. The combination of anti-CEA/GOx@ZnCPs in the immunoassay triggers a cascade reaction involving GOx and MnO2 nanosheets, leading to the generation of an amplified colorimetric signal through self-supplying oxygen. This colorimetric immunoassay exhibits a linear response ranging from 2 to 180 ng mL-1 CEA and has a detection limit of 50 pg mL-1. The practicality of this colorimetric immunoassay in biological matrices was demonstrated by the successful determination of CEA in serum samples with good recovery and precision. We believe that this study will pave the way to rationally design multifunctional CP-based composites for a wide range of applications in bioanalysis.

Degradation of Penicillinic Antibiotics and β-Lactamase Enzymatic Catalysis in a Biomimetic Zn-Based Metal-Organic Framework

β-Lactam antibiotics are one of the most commonly prescribed drugs to treat bacterial infections. However, their use has been somehow limited given the emergence of bacteria with resistance mechanisms, such as β-lactamases, which inactivate them by degrading their four-membered β-lactam rings. So, a total knowledge of the mechanisms governing the catalytic activity of β-lactamases is required. Here, we report a novel Zn-based metal-organic framework (MOF, 1), possessing functional channels capable to accommodate and interact with antibiotics, which catalyze the selective hydrolysis of the penicillinic antibiotics amoxicillin and ceftriaxone. In particular, MOF 1 degrades, very efficiently, the four-membered β-lactam ring of amoxicillin, acting as a β-lactamase mimic, and expands the very limited number of MOFs capable to mimic catalytic enzymatic processes. Combined single-crystal X-ray diffraction (SCXRD) studies and density functional (DFT) calculations offer unique snapshots on the host-guest interactions established between amoxicillin and the functional channels of 1. This allows to propose a degradation mechanism based on the activation of a water molecule, promoted by a Zn-bridging hydroxyl group, concertedly to the nucleophilic attack to the carbonyl moiety and the cleaving of C-N bond of the lactam ring.

Application and Development Prospect of Nanoscale Iron Based Metal-Organic Frameworks in Biomedicine

Metal-organic frameworks (MOFs) are coordination polymers that comprise metal ions/clusters and organic ligands. MOFs have been extensively employed in different fields (eg, gas adsorption, energy storage, chemical separation, catalysis, and sensing) for their versatility, high porosity, and adjustable geometry. To be specific, Fe2+/Fe3+ exhibits unique redox chemistry, photochemical and electrical properties, as well as catalytic activity. Fe-based MOFs have been widely investigated in numerous biomedical fields over the past few years. In this study, the key index requirements of Fe-MOF materials in the biomedical field are summarized, and a conclusion is drawn in terms of the latest application progress, development prospects, and future challenges of Fe-based MOFs as drug delivery systems, antibacterial therapeutics, biocatalysts, imaging agents, and biosensors in the biomedical field.

MOFganic Chemistry: Challenges and Opportunities for Metal-Organic Frameworks in Synthetic Organic Chemistry

Metal-organic frameworks (MOFs) are porous, crystalline solids constructed from organic linkers and inorganic nodes that have been widely studied for applications in gas storage, chemical separations, and drug delivery. Owing to their highly modular structures and tunable pore environments, we propose that MOFs have significant untapped potential as catalysts and reagents relevant to the synthesis of next-generation therapeutics. Herein, we outline the properties of MOFs that make them promising for applications in synthetic organic chemistry, including new reactivity and selectivity, enhanced robustness, and user-friendly preparation. In addition, we outline the challenges facing the field and propose new directions to maximize the utility of MOFs for drug synthesis. This perspective aims to bring together the organic and MOF communities to develop new heterogeneous platforms capable of achieving synthetic transformations that cannot be replicated by homogeneous systems.

Engineering of metal-organic frameworks (MOFs) for thermometry

Metal-organic frameworks (MOFs ) are excellent candidates for use in chemistry, material sciences and engineering thanks to their interesting qualitative features and potential applications. Quite interestingly, the luminescence of MOFs can be engineered by regulation of the ligand design, metal ion selection and encapsulation of guest molecules within the MOF cavity. Temperature is a very crucial physical parameter and the market share of temperature sensors is rapidly expanding with technology and medicinal advancement. Among the wide variety of available temperature sensors, recently MOFs have emerged as potential temperature sensors with the capacity to precisely measure the temperature. Lanthanide-based thermometry has advantages because of its ratiometric response ability, high quantum yield and photostability, and therefore lanthanide-based MOFs were initially focused on to construct MOF thermometers. As science and technology have gradually changed, it has been observed that with the inclusion of dye, quantum dots, etc. within the MOF cavity, it is possible to develop MOF-based thermometry. This review consolidates the recent advances of MOF-based ratiometric thermometers and their mechanism of energy transfer for determining the temperature (thermal sensitivity and temperature uncertainty). In addition, some fundamental points are also discussed, such as concepts for guiding the design of MOF ratiometric thermometers, thermometric performance and tuning the properties of MOF thermometers.

Molecular Catalysis of Energy Relevance in Metal-Organic Frameworks: From Higher Coordination Sphere to System Effects

The modularity and synthetic flexibility of metal-organic frameworks (MOFs) have provoked analogies with enzymes, and even the term MOFzymes has been coined. In this review, we focus on molecular catalysis of energy relevance in MOFs, more specifically water oxidation, oxygen and carbon dioxide reduction, as well as hydrogen evolution in context of the MOF-enzyme analogy. Similar to enzymes, catalyst encapsulation in MOFs leads to structural stabilization under turnover conditions, while catalyst motifs that are synthetically out of reach in a homogeneous solution phase may be attainable as secondary building units in MOFs. Exploring the unique synthetic possibilities in MOFs, specific groups in the second and third coordination sphere around the catalytic active site have been incorporated to facilitate catalysis. A key difference between enzymes and MOFs is the fact that active site concentrations in the latter are often considerably higher, leading to charge and mass transport limitations in MOFs that are more severe than those in enzymes. High catalyst concentrations also put a limit on the distance between catalysts, and thus the available space for higher coordination sphere engineering. As transport is important for MOF-borne catalysis, a system perspective is chosen to highlight concepts that address the issue. A detailed section on transport and light-driven reactivity sets the stage for a concise review of the currently available literature on utilizing principles from Nature and system design for the preparation of catalytic MOF-based materials.

The enhancement of enzyme cascading via tetrahedral DNA framework modification

Enzyme clustering is widely used in many organisms to increase the catalytic efficiency of cascade reactions. Inspired by nature, organizing enzymes within a cascade reaction also draws much attention in both basic research and industrial processes. An important step for organizing enzymes precisely in vitro is enzyme modification. However, modifying enzymes without sacrificing their activity remains challenging until now. For example, labeling enzymes with DNA, one of the well-established enzyme modification methods, has been shown to significantly reduce the enzymatic activity. Herein we report an enzyme conjugation method that can rescue the reduction of enzymatic activity caused by DNA labeling. We demonstrate that immobilizing DNA-modified enzymes on the vertex of TDNs (tetrahedral DNA nanostructures) enhances the enzymatic activity compared with their unmodified counterparts. Using this strategy, we have further developed an ultra-sensitive and high-throughput electrochemical biosensor for sarcosine detection, which holds great promise for prostate cancer screening.

Construction of nano-sized FOX-7/ZIF-8 composites for fast decomposition and reduced sensitivity

Herein, novel nano-sized 1,1-diamino-2,2-dinitroethylene (C₂H₄N₄O₄, FOX-7)/zeolitic imidazolate framework-8 (ZIF-8) composites are constructed by facile liquid-assisted mechanochemical reactions. In contrast to two-step thermal decomposition of raw FOX-7, the prepared FOX-7/ZIF-8 composites demonstrate a single high-intensity exothermal decomposition attributed to the catalysis of ZIF-8. Benefiting from nano-sized energetic materials and the buffering effect of ZIF-8, the mechanical sensitives of FOX-7/ZIF-8 composites are decreased.

Low-temperature propane oxidative dehydrogenation over UiO-66 supported vanadia catalysts: Role of support confinement effects

Overoxidation is the principal barrier against commercializing propane oxidative dehydrogenation (PODH) catalysts for propylene production. The current approach to reducing overoxidation, i.e., coating the non-selective support surface with a monolayer of active phase, can itself increase the probability of overoxidation of the produced propylene due to polymerization of active phase species. Incorporating the "confinement agents" onto the metal oxide support might be considered as an alternative solution to prevent hydrocarbons from reaching the support and overoxidizing. Herein, the UiO-66 metal-organic framework, which contains numerous organic ligands connected to the zirconia nodes, was used as support for the vanadia active phase to highlight the role of support's confinement effects on the overall catalytic performance toward the PODH. The UiO-66 supported vanadia catalysts with various vanadium loadings were fabricated via an ultrasonic-assisted wet impregnation procedure. The catalytic function is related to the underlying chemical processes at catalyst surfaces using physicochemical characterization techniques, PODH performance measurements, and machine learning tools. The results showed that the catalyst with a relatively low vanadia density of 2.7 nm-2, equivalent to less than half of the entire support surface coverage, could achieve propylene productivity of 4.43 [Formula: see text] , propane conversion of 17.1%, and propylene selectivity of 49.7% at 350 °C.

In Situ Implantation of Bi2S3 Nanorods into Porous Quasi-Bi-MOF Architectures: Enabling Synergistic Dissociation of Borohydride for an Efficient and Fast Catalytic Reduction of 4-Nitrophenol

Catalytic hydrogenation reduction based on sodium borohydride (NaBH₄) has gained attention as an appealing "one-stone-two-birds" approach for the simultaneous elimination of nitroaromatic pollutants and the production of high-value aminoaromatics under mild conditions. However, the slow kinetics of NaBH₄ dissociation on the surface of catalysts restrict the catalytic hydrogenation reduction efficiency. Herein, we report an intelligent localized sulfidation strategy for an in situ implantation of Bi₂S₃ nanorods within quasi-Bi-MOF architectures (Bi₂S₃@quasi-Bi-MOF) by fine-tuning the pyrolysis temperature. In this novel Bi₂S₃@quasi-Bi-MOF, the porous quasi-Bi-MOF enables efficient adsorption of BH₄^- and 4-nitrophenol (4-NP), while Bi₂S₃ facilitates the BH₄^- dissociation to form H_ads* species adsorbed on the catalyst surface. Benefiting from the synergistic structure, Bi₂S₃@quasi-Bi-MOF exhibits excellent performance for the catalytic reduction of 4-NP, delivering a high turnover frequency (TOF) of 1.67 × 10^-4 mmol mg^-1 min^-1 and an extremely high normalized rate constant (k_nor) of 435298 s^-1 g^-1. The kinetic analysis and electrochemical tests indicate that this catalytic hydrogenation reduction follows the Langmuir-Hinshelwood mechanism. This study enriches the synthetic strategy of MOF-based derivatives and offers a new catalytic platform for hydrogenation reduction reactions.

Multifunctional luminescent Zr(IV)-MOF for rapid and efficient detection of vanillin, CrO42- and Cr2O72- ions

Fast and efficient detection of pollutants in the food or wastewater is an urgent need for protecting human health and ecological environment. Herein, a luminescent Zr(IV)-MOF (HBU-20) has been conveniently synthesized. It could be used as a fluorescent probe for detection of vanillin, CrO₄^2-, and Cr₂O₇^2- in aqueous medium. All the fluorescence response time is less than 10 s and the detection limits of vanillin, CrO₄^2- and Cr₂O₇^2- achieve 0.38 μM, 0.065 μM and 0.0089 μM, respectively. Interestingly, common anions, cations and amino acids in the solution can not affect the fluorescence detection. Meanwhile, the fluorescence detection process can be successfully implemented even under strong acid or strong alkaline conditions. Further research shows that the inner filter effect (IFE) plays a major role in the sensing process. The rapid and sensitive fluorescence responses indicate that the compound is a promising multifunctional probe for sensing toxic substance. The results can provide an important reference for the design of new fluorescent probes.

Electrical bistability based on metal-organic frameworks

Electrical bistability existing in biochemical networks is critical for the proper functionalization of living systems. The development of artificial materials with electrical bistability begun to attract much interest due to their broad application prospects, especially in the field of memristors. Metal-organic frameworks (MOFs) have advantages in regular pores, crystallinity, structural designability and easy functionalization, which can promote the construction of novel MOF-based memristors and facilitate a better understanding of switching mechanisms. Here, we highlight recent advances in electrically bistable MOFs as memristors, and discuss their switching mechanisms, including interfacial reaction, proton-transfer mechanism, metal ion migration, charge trapping/detrapping and other mechanisms. Challenges and future perspectives are also presented.

Recent advances in the tuning of the organic framework materials - The selections of ligands, reaction conditions, and post-synthesis approaches

Organic framework materials, particularly metal-organic frameworks (MOFs), graphene-organic frameworks (GOFs), and covalent organic frameworks (COFs), have led to the revolution across fields including catalysts, sensors, gas capture, and biology mainly owing to their ultra-high surface area-to-volume ratio, on-demand tunable crystal structures, and unique surface properties. While the wet chemistry routes have been the predominant synthesis approach, the crystal phase, morphological parameters, and physicochemical properties of organic framework materials are largely affected by various synthesis parameters and precursors. In this work, we specifically review the influences of synthesis parameters towards crystal structures and chemical compositions of organic framework materials, including selected ligand types and lengths, reaction temperature/solvent/reactant compositions, as well as post-synthesis modification approaches. More importantly, the subsequent impacts on the general electronic, mechanical, surface chemical, and thermal properties as well as the consequent variation in performances towards catalytic, desalination, gas sensing, and gas storage applications are critically discussed. Finally, the current challenges and prospects of organic framework materials are provided.

Activation of Cadmium–Imidazole Buffering Coordination Polymer by Sulfur-Doping for the Enhancement of Photocatalytic Degradation of Cationic and Anionic Dyes Under Visible Light

The buffering Cadmium–Imidazole Coordination Polymer (Cd–Im-CP) was synthesized hydrothermally from cadmium chloride and imidazole at 70 °C and then was subjected to doping- by the non-metal sulfur using Na2S solution as a novel modification strategy to produce S–Cd–Im CPs. To investigate doping nature and its effects, Cd–Im CP and S–Cd–Im CPs were characterized applying different analyses techniques, FTIR, Raman, PXRD, SEM/EDX, TGA, and UV–Vis DRS analyses. Characterizations showed the successful chemical doping of sulfur. The inclusion of sulfur within chemical CP structure caused narrowing of material’s bandgap from 4.55 and 3.4 eV to 4.25 and 2.35 eV for S–Cd–Im CPs allowing it for photoresponse towards Visible-light. Both Cd–Im CP and S–Cd–Im CPs were applied for photocatalytic degradation of the selected dyes methylene blue (MB),and methyl orange (MO) employing visible and UV irradiations considering three different initial pH levels to investigate the consequence of sulfur doping. After eliminating the photolysis effect, the best degradation by S–Cd–Im CPs was recorded for MB at initial pH 4 being 13 fold that is for Cd–Im CP. The highest apparent turnover frequencies are 1.2 × 10−3 h−1 for MB at initial pH 10 and 1.03 × 10−4 h−1 for MO at initial pH 4 are given by 10S–Cd–IM CP under Visible-light. Generally, S–Cd–Im CPs remarkably improved photocatalysis degradation of both the dyes for all initial pH levels under Visible-light.

A mesoporous metal–organic framework used to sustainably release copper(ii) into reducing aqueous media to promote the CuAAC click reaction

The mesoporous metal–organic framework Cr-MIL-101-NH₂ (MOF1) has been used to encapsulate, by a simple impregnation method, large amounts of copper sulfate. The resulting loaded material, Cu@MOF1, was successfully employed to slowly release copper(ii) into an appropriate reaction medium in which the reducing agent sodium ascorbate reduces copper(ii) to copper(i), thus allowing the well-known copper(i)-catalyzed alkyne–azide cycloaddition (CuAAC) “click” reaction to proceed in the absence of potentially high local copper(i) concentrations. The use of a MOF-based controlled copper release system such as Cu@MOF1 may be relevant for copper(i)-catalyzed reactions having substrates that could be degraded by potentially high local concentrations of copper(i). The copper chelating ligand TBTA (tris(benzyltriazolylmethyl)amine), a very useful ligand for click chemistry, has been successfully attached to the pores of MOF1. The resulting TBTA-functionalized MOF (MOF3) was compared with its non-functionalized version (MOF1). At copper loadings of ca. 3 mmol g⁻¹, the results revealed that the performances of the two materials are strikingly similar. Upon immersion in methanol/water (95/5) containing sodium ascorbate, both materials slowly released copper encapsulated in their pores and could be recovered and reused efficiently for up to five reaction cycles without reloading with metal ion, while allowing the CuAAC reaction to proceed with excellent conversion rates and yields.

Cr-MIL-101-NH₂ (MOF1) has been used to encapsulate large amounts of copper sulfate and the resulting loaded material, Cu@MOF1, was successfully used to promote the CuAAC click reaction.

Folic acid modified UiO-66 nano drug carrier for combination therapy

The drug delivery system which called RB-Drug@UiO-66-FA can release anticancer drugs slowly in an acidic environment, and generate 1O2 under light exposure, achieving the effect of chemotherapy–photodynamic therapy.

Immobilizing a homogeneous manganese catalyst into MOF pores for α-alkylation of methylene ketones with alcohols

An encapsulation strategy via nano-confinement of a homogeneous manganese–phenanthroline complex into MOF pores selectively produced functionalized branched ketones.

Mechanistically Scoping Cell-Free and Cell-Dependent Artificial Scaffolds in Rebuilding Skeletal and Dental Hard Tissues

Rebuilding mineralized tissues in skeletal and dental systems remains costly and challenging. Despite numerous demands and heavy clinical burden over the world, sources of autografts, allografts, and xenografts are far limited, along with massive risks including viral infections, ethic crisis, and so on. Per such dilemma, artificial scaffolds have emerged to provide efficient alternatives. To date, cell-free biomimetic mineralization (BM) and cell-dependent scaffolds have both demonstrated promising capabilities of regenerating mineralized tissues. However, BM and cell-dependent scaffolds have distinctive mechanisms for mineral genesis, which makes them methodically, synthetically, and functionally disparate. Herein, these two strategies in regenerative dentistry and orthopedics are systematically summarized at the level of mechanisms. For BM, methodological and theoretical advances are focused upon; and meanwhile, for cell-dependent scaffolds, it is demonstrated how scaffolds orchestrate osteogenic cell fate. The summary of the experimental advances and clinical progress will endow researchers with mechanistic understandings of artificial scaffolds in rebuilding hard tissues, by which better clinical choices and research directions may be approached.

Heterogenizing a Homogeneous Nickel Catalyst Using Nanoconfined Strategy for Selective Synthesis of Mono- and 1,2-Disubstituted Benzimidazoles

A homogeneous Ni-phenanthroline catalyst was successfully immobilized into the cavities of a metal-organic framework, ZIF-8. The as-synthesized heterogeneous catalyst, Ni-Phen@ZIF, represents the first MOF based catalyst that enables dehydrogenative coupling of alcohols with aromatic diamines for selective synthesis of both mono- and 1,2-disubstituted benzimidazoles. The catalyst survived under harsh basic conditions, characterized by SEM, TEM, BET, PXRD, and EDX elemental mappings. The presence of the nanoconfined Ni-phenanthroline complex and the formation of extra Lewis acid sites during catalysis in the Ni-Phen@ZIF structure, confirmed by TPD analysis and kinetic experiments, might be responsible for higher activity and selectivity.

Low-Valent Metal Ions as MOF Pillars: A New Route Toward Stable and Multifunctional MOFs

PCM-102 is a new organophosphine metal-organic framework (MOF) featuring diphosphine pockets that consist of pairs of offset trans-oriented P(III) donors. Postsynthetic addition of M(I) salts (M = Cu, Ag, Au) to PCM-102 induces single-crystal to single-crystal transformations and the formation of trans-[P₂M]⁺ solid-state complexes (where P = framework-based triarylphosphines). While the unmetalated PCM-102 has low porosity, the addition of secondary Lewis acids to install rigid P-M-P pillars is shown to dramatically increase both stability and selective gas uptake properties, with N₂ Brunauer-Emmett-Teller surface areas >1500 m² g^-1. The Ag(I) analogue can also be obtained via a simple, one-pot peri-synthetic route and is an ideal sacrificial precursor for materials with mixed bimetallic M^A/M^B pillars via postsynthetic, solvent-assisted metal exchange. Notably, the M-PCM-102 family of MOFs contain periodic trans-[P₂M]⁺ sites that are free of counter anions, unlike traditional analogous molecular complexes, since the precursor PCM-102 MOF is monoanionic, enabling access to charge-neutral metal-pillared materials. Four M-PCM-102 materials were evaluated for the separation of C2 hydrocarbons. The separation performance was found to be tunable based on the metal(s) incorporated, and density functional theory was employed to elucidate the nature of the unusual observed sorption preference, C₂H₂ > C₂H₆ > C₂H₄.

Metal-Organic Frameworks as a Versatile Materials Platform for Unlocking New Potentials in Biocatalysis

Biocatalysts immobilization with nanomaterials has promoted the development of biocatalysis significantly and made it an indispensable part of catalysis industries nowadays. Metal-organic frameworks (MOFs), constructed from organic linkers and metal ions or clusters, have raised significant interests for biocatalysts immobilization in recent years. The diversity of building units, molecular-scale tunability, and modular synthetic routes of MOFs greatly expand its ability as the host to integrate with biocatalysts. In this review, the general synthetic strategies of MOFs with biocatalysts are first summarized. Then, the recent progress of MOFs as a versatile host for a series of biocatalysts, including natural enzymes, nanozymes, and organism-based biocatalysts, followed by the introduction of MOFs themselves as biocatalysts, is discussed. Furthermore, the stimuli-responsive properties of MOFs themselves or the additional functionalization of protein, polymer, and peptide within/on MOF that enable the biocatalysts with the controllable and tunable behavior are also summarized, which could unlock new potentials in biocatalysis. Finally, a perspective of the upcoming challenges, potential impacts, and future directions of biocatalytic MOFs is provided.

Heterogeneous nanozymatic activity of Hf oxo-clusters embedded in a metal-organic framework towards peptide bond hydrolysis

Materials with enzyme-like activities and proteolytic potential are emerging as a robust and effective alternative to natural enzymes. Herein, a Hf₆O₈-based NU-1000 metal organic framework (Hf-MOF) is shown to act as a heterogeneous catalyst for the hydrolysis of peptide bonds under mild conditions. In the presence of Hf-MOF, a glycylglycine model dipeptide was hydrolysed with a rate constant of k_obs = 8.33 × 10^-7 s^-1 (half-life (t_1/2) of 231 h) at 60 °C and pD 7.4, which is significantly faster than the uncatalyzed reaction. Other Gly-X peptides (X = Ser, Asp, Ile, Ala, and His) were also smoothly hydrolysed under the same conditions with similar rates, except for the faster reactions observed for Gly-His and Gly-Ser. Moreover, the Hf₆O₈-based NU-1000 MOF also exhibits a high selectivity in the cleavage of a protein substrate, hen egg white lysozyme (HEWL). Our results suggest that embedding Hf₆O₈ oxo-clusters is an efficient strategy to conserve the hydrolytic activity while smoothing the strong substrate adsorption previously observed for a discrete Hf oxo-cluster that hindered further development of its proteolytic potential. Furthermore, comparison with isostructural Zr-NU-1000 shows that although the Hf variant afforded the same cleavage pattern towards HEWL but slightly slower reaction rates, it exhibited a larger stability window and a better recyclability profile. The results suggest that these differences originate from the intrinsic differences between Hf^IV and Zr^IV centers, and from the lower surface area of Hf-NU-1000 in comparison to Zr-NU-1000.

Chemically Robust and Bifunctional Co(II)-Framework for Trace Detection of Assorted Organo-toxins and Highly Cooperative Deacetalization-Knoevenagel Condensation with Pore-Fitting-Induced Size-Selectivity

Acute detection of assorted classes of organo-toxins in a practical environment is an important sustainable agenda, whereas cooperative and recyclable catalysis can mitigate hazards by minimizing energy requirements and reducing waste generation. We constructed an acid-/base-stable Co(II)-framework with a unique network topology, wherein unidirectional porous channels are decorated by anionic [Co₂(μ₂-OH)(COO)₄(H₂O)₃] secondary building units and neutral [CoN₂(COO)₂] nodes. An intense luminescent signature of the hydrolytically robust framework is harnessed for the selective, fast-responsive, and regenerable detection of two detrimental organo-aromatics, 4-aminophenol (4-AP) and 2,4,6-trinitrophenol (TNP). Alongside remarkable quenching, their nanomolar detection limits (4-AP: 99.5 nM; TNP: 67.2 nM) rank among the lowest reported values in water and corroborate their ultra-sensitivity. Density functional theory (DFT) calculations verify the electron-transfer route of sensing through portraying redistribution of energy levels of molecular orbitals in a three-dimensional network by each analyte and further envisages non-covalent host-guest interactions. Benefiting from the concurrent existence of an open-metal site and a triphenylamine-moiety-functionalized ligand, the activated framework acts as an outstandingly cooperative heterogeneous catalyst in deacetalization-Knoevenagel condensation under mild conditions. The acid-base dual catalysis is detailed for the first time from combined inputs of control experiments and DFT validations. To the best of tandem reaction, larger-sized substrate exhibits insignificant conversion, and certifies rarest pore-fitting induced size-selectivity.

Evaluating the Robustness of Metal-Organic Frameworks for Synthetic Chemistry

Metal-organic frameworks (MOFs) are emerging as sustainable reagents and catalysts with promising applications in synthetic chemistry. Although the hydrothermal stabilities of MOFs have been well studied, their robustness toward various reagents, including acids, bases, nucleophiles, electrophiles, oxidants, and reductants, remains poorly characterized. As such, heterogeneous platforms for promising catalysts are generally identified on an ad hoc basis and have largely been limited to carboxylate frameworks to date. To address these limitations, here we systematically characterize the robustness of 17 representative carboxylate, salicylate, and azolate MOFs toward 30 conditions representing the scope of synthetic organic chemistry. Specifically, analysis of the full width at half-maximum of powder X-ray diffraction patterns, as well as infrared spectroscopy, 77 K N2 adsorption measurements, and scanning electron microscopy in select cases are employed to appraise framework degradation and dissolution under a range of representative conditions. Our studies demonstrate that azolate MOFs, such as Fe2(bdp)3 (bdp2- = 4,4'-(1,4-phenylene)bis(pyrazolate)), generally possess excellent chemical stabilities under myriad conditions. In addition, we find that carboxylate and salicylate frameworks possess complementary stabilities, with carboxylate MOFs possessing superior robustness toward acids, electrophiles, and oxidants, and salicylate MOFs demonstrating improved robustness toward bases, nucleophiles, and reductants. The guidelines provided herein should facilitate the rational design of robust frameworks for applications in synthetic chemistry and guide the development of new strategies for the postsynthetic modification of MOFs as well.

Metal–Organic Frameworks as Versatile Platforms for Organometallic Chemistry

Metal–organic frameworks (MOFs) are emerging porous materials with highly tunable structures developed in the 1990s, while organometallic chemistry is of fundamental importance for catalytic transformation in the academic and industrial world for many decades. Through the years, organometallic chemistry has been incorporated into functional MOF construction for diverse applications. Here, we will focus on how organometallic chemistry is applied in MOF design and modifications from linker-centric and metal-cluster-centric perspectives, respectively. Through structural design, MOFs can function as a tailorable platform for traditional organometallic transformations, including reaction of alkenes, cross-coupling reactions, and C–H activations. Besides, an overview will be made on other application categories of organometallic MOFs, such as gas adsorption, magnetism, quantum computing, and therapeutics.

Confinement-guided photophysics in MOFs, COFs, and cages

In this review, the dependence of the photophysical response of chromophores in the confined environments associated with crystalline scaffolds, such as metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), and molecular cages, has been carefully evaluated. Tunability of the framework aperture, cavity microenvironment, and scaffold topology significantly affects emission profiles, quantum yields, or fluorescence lifetimes of confined chromophores. In addition to the role of the host and its effect on the guest, the methods for integration of a chromophore (e.g., as a framework backbone, capping linker, ligand side group, or guest) are discussed. The overall potential of chromophore-integrated frameworks for a wide-range of applications, including artificial biomimetic systems, white-light emitting diodes, photoresponsive devices, and fluorescent sensors with unparalleled spatial resolution are highlighted throughout the review.

Biohybrid Systems for Improved Bioinspired, Energy-Relevant Catalysis

Biomimetic catalysts, ranging from small-molecule metal complexes to supramolecular assembles, possess many exciting properties that could address salient challenges in industrial-scale manufacturing. Inspired by natural enzymes, these biohybrid catalytic systems demonstrate superior characteristics, including high activity, enantioselectivity, and enhanced aqueous solubility, over their fully synthetic counterparts. However, instability and limitations in the prediction of structure-function relationships are major drawbacks that often prevent the application of biomimetic catalysts outside of the laboratory. Despite these obstacles, recent advances in synthetic enzyme models have improved our understanding of complicated biological enzymatic processes and enabled the production of catalysts with increased efficiency. This review outlines important developments and future prospects for the design and application of bioinspired and biohybrid systems at multiple length scales for important, biologically relevant, clean energy transformations.

Metal-Organic Frameworks in Oxidation Catalysis with Hydrogen Peroxide

In recent years, metal–organic frameworks (MOFs) have received increasing attention as selective oxidation catalysts and supports for their construction. In this short review paper, we survey recent findings concerning use of MOFs in heterogeneous liquid-phase selective oxidation catalysis with the green oxidant–aqueous hydrogen peroxide. MOFs having outstanding thermal and chemical stability, such as Cr(III)-based MIL-101, Ti(IV)-based MIL-125, Zr(IV)-based UiO-66(67), Zn(II)-based ZIF-8, and some others, will be in the main focus of this work. The effects of the metal nature and MOF structure on catalytic activity and oxidation selectivity are analyzed and the mechanisms of hydrogen peroxide activation are discussed. In some cases, we also make an attempt to analyze relationships between liquid-phase adsorption properties of MOFs and peculiarities of their catalytic performance. Attempts of using MOFs as supports for construction of single-site catalysts through their modification with heterometals will be also addressed in relation to the use of such catalysts for activation of H2O2. Special attention is given to the critical issues of catalyst stability and reusability. The scope and limitations of MOF catalysts in H2O2-based selective oxidation are discussed.

A robust heterogeneous Co-MOF catalyst in azide–alkyne cycloaddition and Friedel–Crafts reactions as well as hydrosilylation of alkynes

A robust Co(ii) MOF with high stability was prepared to promote the azide–alkyne cycloaddition reaction, Friedel–Crafts reactions of indoles and hydrosilylation reactions of alkynes.

Synthesis of Three Dimensional Cs-γ-CD-MOFs and the Adsorption of Myricetin

A new Cs-γ-CD-MOF material obtained in colourless large crystals and with a three-dimensional porous structure containing coordinated by cesium ions and γ-cyclodextrin was synthesised by an improved vapour diffusion method. The chemical formula of the Cs-γ-CD-MOF material was C24H34CsO20, with the I4 space group. Compared with the traditional solvent vapour diffusion method (7 days), this method is advantageous for rapid crystal formation (1 day). Simultaneously, the drug adsortion capacity of γ-CD and Cs-γ-CD-MOFs for myricetin was compared and the results indicated that Cs-γ-CD-MOFs (280.05 mg g−1) have a higher drug adsorption capacity than γ-CD (142.92 mg g−1). Finally, the energy and conformation of the Cs-γ-CD-MOF material for adsorbing the drug myricetin were obtained through molecular docking.

Bent-bis(triazolyl)-based coordination polymers tuned by dicarboxylate ligands: syntheses, structures and properties

Seven new coordination polymers based on the bent 1,1'-(oxybis(1,4-phenylene))-bis(1H-1,2,4-triazole) ligand, with diverse structures and novel topologies, that are directed by the dicarboxylate ligands.

Auxiliary ligand-modulated trisimidazole-based coordination polymers: syntheses, structures and photoluminescence properties

Five coordination polymers having 1,3,5-tris(1-imidazolyl)benzene and the varied O-donor auxiliary ligands were designed and synthesized. Further, the auxiliary ligands modulated these complexes with structural diversities and novel topologies.

Stepping stones to the future of haemoglobin-based blood products: clinical, preclinical and innovative examples

Critical overview of the different oxygen therapeutics developed so far to be used when donor blood is not available.

Postsynthetic Metalated MOFs as Atomically Dispersed Catalysts for Hydroformylation Reactions

A manganese-based metal-organic framework with dipyrazole ligands has been metalated with atomically dispersed Rh and Co species and used as a catalyst for the hydroformylation of styrene. The Rh-based materials exhibited excellent conversion at 80 °C with complete chemoselectivity, high selectivity for the branched aldehyde, high recyclability, and negligible metal leaching.

A Critical Review on Metal-Organic Frameworks and Their Composites as Advanced Materials for Adsorption and Photocatalytic Degradation of Emerging Organic Pollutants from Wastewater

Water-borne emerging pollutants are among the greatest concern of our modern society. Many of these pollutants are categorized as endocrine disruptors due to their environmental toxicities. They are harmful to humans, aquatic animals, and plants, to the larger extent, destroying the ecosystem. Thus, effective environmental remediations of these pollutants became necessary. Among the various remediation techniques, adsorption and photocatalytic degradation have been single out as the most promising. This review is devoted to the compilations and analysis of the role of metal-organic frameworks (MOFs) and their composites as potential materials for such applications. Emerging organic pollutants, like dyes, herbicides, pesticides, pharmaceutical products, phenols, polycyclic aromatic hydrocarbons, and perfluorinated alkyl substances, have been extensively studied. Important parameters that affect these processes, such as surface area, bandgap, percentage removal, equilibrium time, adsorption capacity, and recyclability, are documented. Finally, we paint the current scenario and challenges that need to be addressed for MOFs and their composites to be exploited for commercial applications.