Porphyrinic Metal–Organic Frameworks Installed with Brønsted Acid Sites for Efficient Tandem Semisynthesis of Artemisinin

Interface-regulated S-type core-shell PCN-224@TiO2 heterojunction for visible-light-driven generation of singlet oxygen for selective photooxidation of 2-chloroethyl ethyl sulfide

Selective oxidation of sulfur mustard gas (HD) to non-toxic sulfoxide by the visible-light-catalyzed generation of singlet oxygen (1O2) is a promising degradation strategy. Although PCN-224 can absorb visible light, it suffers from rapid electron-hole recombination and low redox capacity, which limits the performance of HD degradation. Titanium dioxide (TiO2) is an excellent photocatalyst but it lacks visible-light-activity in degrading HD. In this study, PCN-224@TiO2 heterojunction with S-type core-shell structure was synthesized by in-situ growth method to prolong the visible light absorption capacity of TiO2 and inhibit the rapid recombination of PCN-224. The interface formation and internal electric field were optimized by adjusting the Zr/Ti ratio to enhance the charge transfer, redox capacity, electron-hole separation, and visible light absorption. In this study, the formation of heterojunction composites based on Zr-O-Ti linkages is demonstrated by a series of characterization methods. It is demonstrated by experiments and theoretical calculations that PCN-224@TiO2 can generate nearly 100 % 1O2 under visible light conditions without a sacrificial agent, resulting in efficient and selective oxidation of 2-chloroethyl ethyl sulfide (CEES), a simulant of HD, to non-toxic sulfoxide form.

Red light-triggered release of ROS and carbon monoxide for combinational antibacterial application

The abuse of antibiotics has led to the emergence of a wide range of drug-resistant bacteria. To address the challenge of drug-resistant bacterial infections and related infectious diseases, several effective antibacterial strategies have been developed. To achieve enhanced therapeutic effects, combinational treatment approaches should be employed. With this in mind, a metal-organic framework (MOF) based nanoreactor with integrated photodynamic therapy (PDT) and gas therapy which can release reactive oxygen species (ROS) and carbon monoxide (CO) under red light irradiation has been developed. The release of ROS and CO under red light irradiation exerts a preferential antibacterial effect on Gram-positive/Gram-negative bacteria. The bactericidal effects of ROS and CO on Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus (MRSA) are better than ROS only, showing a combinational antibacterial effect. Furthermore, the fluorescence emission properties of porphyrin moieties can be leveraged for real-time tracking and imaging of the nanoreactors. The simple preparation procedures of this material further enhance its potential as a versatile and effective antibacterial candidate, thereby presenting a new strategy for PDT and gas combinational treatment.

De Novo Synthesis of Acridone-Based Zn-Metal-Organic Framework (Zn-MOF) as a Photocatalyst: Application for Visible Light-Mediated Oxidation of Sulfides and Enaminones

Acridone, a cyclic analogue of benzophenone that undergoes efficient intersystem crossing (ISC) to the triplet-excited state with near-unity quantum yield, was elaborated as a 3-connecting triacid linker, i.e., H3AcTA, to develop a photocatalytic metal-organic framework (MOF) for energy transfer applications; the triacid linker inherently features concave shapes, an attribute that is important for the construction of MOFs with significant porosity. Metal ion (Zn2+)-assisted self-assembly of the triacid yielded a Zn-MOF, i.e., Zn-AcTA, with a solvent-accessible volume of ca. 31%. The protection of the acridone chromophore in the MOF in conjunction with a wider cross-section of its absorption in the visible region renders the MOF an excellent heterogeneous photosensitizer for singlet oxygen (1O2) generation by energy transfer to the ground-state triplet oxygen (3O2). It is shown that the Zn-MOF can be applied as a photosensitizing catalyst for visible light-mediated oxidation of various sulfides to sulfoxides and enaminones to amino-esters via 1,2-acyl migration. It is further demonstrated that the photocatalyst can be easily recycled without any loss of catalytic activity and structural integrity. Based on mechanistic investigations, 1O2 is established as the reactive oxygen species in photocatalytic oxidation reactions. The results constitute the first demonstration of rational development of a photocatalytic MOF based on acridone for heterogeneous oxidations mediated by 1O2.

Porphyrin-Based Metal-Organic Framework Materials: Design, Construction, and Application in the Field of Photocatalysis

Metal-organic frameworks (MOFs) are a novel category of porous crystalline materials with an exceptionally high surface area and adjustable pore structure. They possess a designable composition and can be easily functionalized with different units. Porphyrins with conjugated tetrapyrrole macrocyclic structures can absorb light from ultraviolet to visible light regions, and their structures and properties can be facilely regulated by altering their peripheral groups or central metal ions. Porphyrin-based MOFs constructed from porphyrin ligands and metal nodes combine the unique features of porphyrins and MOFs as well as overcoming their respective limitations. This paper reviewed the design and construction, light absorption and charge transfer pathways, and strategy for improving the photocatalytic performance of porphyrin-based MOFs, and highlighted the recent progress in the field of CO2 reduction, hydrogen evolution, organic synthesis, organic pollutant removal, and nitrogen fixation. The intrinsic relationships between the structure and the property of porphyrin-based MOFs received special attention, especially the relationships between the arrangements of porphyrin ligands and metal nods and the charge transfer mechanism. We attempted to provide more valuable information for the design and construction of advanced photocatalysts in the future. Finally, the challenges and future perspectives of the porphyrin-based MOFs are also discussed.

Confining redox-active metal sites in acidic porous scaffolds for the catalytic transformation of lignin-derived phenols to naphthenes

The hydrodeoxygenation transformation of lignin-derived phenols provides an attractive pathway for the production of renewable biofuels; however, harsh process conditions strongly hinder its practical application. Herein, we report a porous metal silicate (PMS) material, PMS-36, which consists of metallic nickel and Lewis acid AlIII sites inside the pores, demonstrating high efficiency in catalyzing the hydrodeoxygenation transformation of guaiacol under mild conditions. PMS-36 also exhibits robust stability, which can be attributed to the strong interaction and charge transfer between metallic Ni and AlIII Lewis acid sites inside the confined pores. This study shows the importance of synergistic and confinement effects in developing high-performance and stable heterogeneous catalysts for the chemical transformation of biomass and its derivatives.

Bioinspired Framework Catalysts: From Enzyme Immobilization to Biomimetic Catalysis

Enzymatic catalysis has fueled considerable interest from chemists due to its high efficiency and selectivity. However, the structural complexity and vulnerability hamper the application potentials of enzymes. Driven by the practical demand for chemical conversion, there is a long-sought quest for bioinspired catalysts reproducing and even surpassing the functions of natural enzymes. As nanoporous materials with high surface areas and crystallinity, metal-organic frameworks (MOFs) represent an exquisite case of how natural enzymes and their active sites are integrated into porous solids, affording bioinspired heterogeneous catalysts with superior stability and customizable structures. In this review, we comprehensively summarize the advances of bioinspired MOFs for catalysis, discuss the design principle of various MOF-based catalysts, such as MOF-enzyme composites and MOFs embedded with active sites, and explore the utility of these catalysts in different reactions. The advantages of MOFs as enzyme mimetics are also highlighted, including confinement, templating effects, and functionality, in comparison with homogeneous supramolecular catalysts. A perspective is provided to discuss potential solutions addressing current challenges in MOF catalysis.

Cu-MOFs based photocatalyst triggered antibacterial platform for wound healing: 2D/2D Schottky junction and DFT calculation

Herein, we developed a multimodal antibacterial nanoplatform via synergism effect including knife-effect, photothermal, photocatalytic induced reactive oxygen species (ROS), and Cu²⁺ inherent attribute. Typically, 0.8-TC/Cu-NS possesses higher photothermal property with the higher photothermal conversion efficiency of 24% and the moderate temperature up to 97 °C. Meanwhile, 0.8-TC/Cu-NS exhibits the more active ROS, ¹O₂ and ·O₂^-. Hence, 0.8-TC/Cu-NS possesses best antibacterial properties against S. aureus and E. coli in vitro with efficiency of 99.94%/99.97% under near-infrared (NIR) light, respectively. In the therapeutic practical use for wound healing of Kunming mice, this system exhibits outstanding curing capacity and good biocompatibility. Based on the electron configuration measurement and density functional theory (DFT) simulation, it is confirmed that the electrons on CB of Cu-TCPP flow fleetingly to MXene trough the interface, with redistribution of charge and band upward bending over Cu-TCPP. As a result, the self-assembled 2D/2D interfacial Schottky junction have made great favor to accelerate photogenerated charges mobility, hamper charge recombination, and increases the photothermal/photocatalytic activity. This work gives us a hint to mostly design the multimodal synergistic nanoplatform under NIR light in biological applications without drug resistance.

A highly robust cluster-based indium(III)-organic framework with efficient catalytic activity in cycloaddition of CO2 and Knoevenagel condensation

The efficient catalytic performance displayed by MOFs is decided by an appropriate charge/radius ratio of defect metal sites, large enough solvent-accessible channels and Lewis base sites capable of polarizing substrate molecules. Herein, the solvothermal self-assembly led to a highly robust nanochannel-based framework of {[In₄(CPDD)₂(μ₃-OH)₂(DMF)(H₂O)₂]·2DMF·5H₂O}_n (NUC-66) with a 56.8% void volume, which is a combination of a tetranuclear cluster [In₄(μ₃-OH)₂(COO)₁₀(DMF)(H₂O)₂] (abbreviated as {In₄}) and a conjugated tetracyclic pentacarboxylic acid ligand of 4,4'-(4-(4-carboxyphenyl)pyridine-2,6-diyl)diisophthalic acid (H₅CPDD). To the best of our knowledge, NUC-66 is a rarely reported {In₄}-based 3D framework with embedded hierarchical triangular-microporous (2.9 Å) and hexagonal-nanoporous (12.0 Å) channels, which are shaped by six rows of {In₄} clusters. After solvent exchange and vacuum drying, the surface of nanochannels in desolvated NUC-66a is modified by unsaturated In³⁺ ions, N_pyridine atoms and μ₃-OH groups, all of which display polarization ability towards polar molecules due to their Lewis acidity or basicity. The catalytic experiments performed showed that NUC-66a had high catalytic activity in the cycloaddition reactions of epoxides with CO₂ under mild conditions, which should be ascribed to its structural advantages including nanoscale channels, rich bifunctional active sites, large surface areas and chemical stability. Moreover, NUC-66a, as a heterogeneous catalyst, could greatly accelerate the Knoevenagel condensation reactions of aldehydes and malononitrile. Hence, this work confirms that the development of rigid nanoporous cluster-based MOFs built on metal ions with a high charge and large radius ratio will be more likely to realize practical applications, such as catalysis, adsorption and separation of gas, etc.

Hybrid Materials Based on Imidazo[4,5-b]porphyrins for Catalytic Oxidation of Sulfides

Heterogenized metalloporphyrin catalysts for oxidation reactions are extensively explored to improve chemical production. In this work, manganese meso-tetraarylporphyrins were immobilized on hydrated mesoporous titanium dioxide (SBET = 705 m2 g−1) through carboxylate or phosphonate anchoring groups separated from the macrocycle by the 2-arylimidazole linker fused across one of the pyrrolic rings of the macrocycle. The element composition of two mesoporous hybrid materials thus obtained were investigated and the integrity of the immobilized complexes was shown by different physicochemical methods. Finally, the catalytic efficiency of the more stable material Mn(TMPIP)/TiO2 with the phosphonate anchor was evaluated in the selective oxidation of sulfides to sulfoxides by molecular oxygen in the presence of isobutyraldehyde (IBA). The heterogenized complex has shown excellent catalytic activity exhibiting a turnover (TON) of ~1100 in a single catalytic run of the sulfoxidation of thioanisole. The catalyst was successfully reused in seven consecutive catalytic cycles.

Metal-porphyrinic framework nanotechnologies in modern agricultural management

Metal-porphyrinic frameworks are an important subclass of metal-organic frameworks (MOFs). These porous materials exhibit a large number of applications for sustainable development and related environmental considerations. Their attractive features include (1) as a free base or metalated with zinc(II) or iron(II or III), they are environmentally benign, and (2) they absorb visible light and are emissive and semi-conducting, making them convenient tools for sensing agrochemicals. But the key feature that makes these nano-sized pristine materials or their composites in many ways superior to most MOFs is their ability to photo-generate reactive oxygen species with visible light, including singlet oxygen. This review describes important issues related to agriculture, including controlled delivery of pesticides and agrochemicals, detection of pesticides and pathogenic metals, elimination of pesticides and toxic metals, and photodynamic antimicrobial activity, and has an important implication for food safety. This comprehensive review presents the progress of the rather rapid developments of these functional and increasingly nano-sized materials and composites in the area of sustainable agriculture.

MOF-enabled confinement and related effects for chemical catalyst presentation and utilization

A defining characteristic of nearly all catalytically functional MOFs is uniform, molecular-scale porosity. MOF pores, linkers and nodes that define them, help regulate reactant and product transport, catalyst siting, catalyst accessibility, catalyst stability, catalyst activity, co-catalyst proximity, composition of the chemical environment at and beyond the catalytic active site, chemical intermediate and transition-state conformations, thermodynamic affinity of molecular guests for MOF interior sites, framework charge and density of charge-compensating ions, pore hydrophobicity/hydrophilicity, pore and channel rigidity vs. flexibility, and other features and properties. Collectively and individually, these properties help define overall catalyst functional behaviour. This review focuses on how porous, catalyst-containing MOFs capitalize on molecular-scale confinement, containment, isolation, environment modulation, energy delivery, and mobility to accomplish desired chemical transformations with potentially superior selectivity or other efficacy, especially in comparison to catalysts in homogeneous solution environments.

The low-temperature NO2 removal by tailoring metal node in porphyrin-based metal-organic frameworks

Nitrogen dioxide (NO₂) is the most toxic and prevalent form of nitrogen oxides (NO_x) pollutant and its removal from ambient air is a pressing challenge. The state-of-the-art deNO_x technologies such as selective catalytic reduction (SCR) can only work at elevated temperatures (>250-300 °C), but ineffective for the NO_x removal under ambient conditions. The adsorptive removal of NO₂ is an alternative approach to SCR, whose success depends on the design of stable adsorbents capable of selectively capturing NO₂ with a highly reversible capacity. Here we synthesized and developed five porphyrin-based metal-organic frameworks (PMOFs) as robust ambient NO₂ adsorbents, including three aluminum-based (Al-PMOF) isostructures, and two zirconium-based (Zr-PMOFs) isostructures. Of them, Al-PMOF stands out to be the most promising candidate by showing the highest NO₂ adsorption capacity (1.85 mmol/g), high stability, and good regenerability (retaining 87% capacity after five cycles of adsorption) at dry conditions. The NO₂ adsorption capacity of Al-PMOF was approximately doubled (3.61 mmol/g) at wet conditions. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed the NO₂ adsorption mechanism - the hydrogen bonding occurs between bridging hydroxyl (-OH) (attached to the metal node) and NO₂ molecules. Our work demonstrates that PMOFs are promising NO₂ adsorbents and will provide guidance for designing robust and reusable adsorbents for efficiently removing NO₂ at ambient temperature.

Enhanced singlet oxygen production over a photocatalytic stable metal organic framework composed of porphyrin and Ag

Porphyrin is an important photosensitizer for singlet oxygen (¹O₂) formation. However, porphyrin derivatives still display low efficiency and difficult recovery. In this work, an Ag-based MOFs (AgTPyP; TPyP, 5,10,15,20-tetra(4-pyridyl) porphyrin) is synthesized. Compared with ligand TPyP, AgTPyP shows nearly 100% conversion and selectivity in the photocatalytic selective oxidation of sulfides to sulfoxides and obvious photodynamic therapeutic effect under visible light. Combined characterizations suggest that ¹O₂ is the only active oxygen species, which is due to the large exciton binding energy and narrow energy gap between the lowest excited singlet state (S₁) and the lowest triplet state (T₁) induced by the presence of Ag⁺ ion. The selectivity and conversion efficiency of five-cycle experiments do not decrease, indicating the excellent stability of AgTPyP. This work provides an alternative approach to simultaneously enhance the exciton effect of porphyrin and stabilize Ag-based photocatalysts.

Impact of Zr6 Node in a Metal-Organic Framework for Adsorptive Removal of Antibiotics from Water

Quinolone-based antibiotics commonly detected in surface, ground, and drinking water are difficult to remove and therefore pose a threat as organic contaminants of aqueous environment. We performed adsorptive removal of quinolone antibiotics, nalidixic acid and ofloxacin, using a zirconium-porphyrin-based metal-organic framework (MOF), PCN-224. PCN-224 exhibits the highest adsorption capacities for both nalidixic acid and ofloxacin among those reported for MOFs to date. The accessible metal sites of Zr metal nodes are responsible for efficient adsorptive removal. This study offers a pragmatic approach to design MOFs optimized for adsorptive removal of antibiotics.

Site-Isolated Azobenzene-Containing Metal-Organic Framework for Cyclopalladated Catalyzed Suzuki-Miyuara Coupling in Flow

Sites isolation of active metals centers, systematically studied in homogeneous systems, has been an alternative to develop low metal consuming, highly active next generation catalysts in heterogeneous condition. Because of the high porosity and facile synthetic procedures, MOF-based catalysts are excellent candidates for heterogenization of well-defined homogeneous catalysts. Herein, we report the direct Pd coordination on the azobenzene linker within a MOF catalyst through a postsynthetic modification method for a Suzuki-Miyaura coupling reaction. The immobilized cyclopalladated complexes in MOFs were analyzed by a series of characterization techniques including XPS, PXRD, and deuterium NMR (2H NMR) spectroscopy. The heterogeneous nature of the catalyst as well as its stability were demonstrated though "hot filtration" and recycling experiments. Furthermore, we demonstrate that the MOF packed column promoted the reaction between phenyl boronic acid and bromobenzene under microflow conditions with a 85% yield continuously for 12 h. This work sheds light on the potential of site-isolated MOF catalysts in efficient, recyclable and continuous flow systems for industrial application.

Structural diversity of nanoscale zirconium porphyrin MOFs and their photoactivities and biological performances

Photoactive MOF-based delivery systems are highly attractive for photodynamic therapy (PDT), but the fundamental interplay among structural parameters and photoactivity and biological properties of these MOFs remains unclear. Herein, porphyrinic MOF isomers (TCPP-MOFs), constructing using the same building blocks into distinct topologies, have been selected as ideal models to understand this problem. Both the intramolecular distances and molecular polarization within TCPP-MOFs isomers collectively contribute to the photoactivity of generating reactive oxygen species. Remarkably, the morphology-determined endocytic pathways and cytotoxicity, as well as good biocompatibility have been confirmed for TCPP-MOF isomers without any chemical modification for the first time. Besides the topology-dependent photoactive regulation, this work also provides in-depth insights into the biological effect from the MOF nanoparticles with controllable structural factors, benefiting further in vivo applications and clinical transformation.

Aqueous Protein-Polymer Bioconjugation via Photoinduced RAFT Polymerization Using High Loading Heterogeneous Catalyst

Light-driven polymerization, such as photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization, enables biological benign conditions and versatile functional polymer structure design, which is readily used in protein-polymer bioconjugates. However, conventional metalloporphyrinic homogeneous catalysts for PET-RAFT polymerization suffer from limited aqueous solubility and tedious purification. Here we demonstrate the design of PET-RAFT photocatalyst from the reticular assembled Zr-porphyrinic metal-organic frameworks (MOFs), along with a biomacromolecule-based chain transfer agent, as efficient bioconjugation tools in water. Our methodology offers manufacturing advantages on bioconjugates under mild conditions such that MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) and cytotoxicity assays have shown the preservation of the protein integrity, bioactivity, and high cell viability after PET-RAFT polymerization. We find that the fast kinetics are benefiting from the ultrahigh loading of metalloporphyrins in MOF-525-Zn. This heterogeneous catalyst also allows us to maintain living characteristics to incorporate myriads of monomers into block copolymers. Other advantages like easy postreaction purification, reusability, and high oxygen tolerance even in an open system are demonstrated. This study provides a tool of highly efficient heterogeneous photocatalysts for polymer-protein bioconjugation in aqueous media and paves the road for biological applications.

Photocatalyst-enzyme hybrid systems for light-driven biotransformation

Enzymes catalyse target reactions under mild conditions with high efficiency, as well as excellent regional-, stereo-, and enantiomeric selectivity. Photocatalysis utilises sustainable and environment-friendly light power to realise efficient chemical conversion. By combining the interdisciplinary advantages of photo- and enzymatic catalysis, the photocatalyst-enzyme hybrid systems have proceeded various light-driven biotransformation with high efficiency under environmentally benign conditions, thus, attracting unparalleled focus during the last decades. It has also been regarded as a promising pathway towards green chemistry utilising ubiquitous solar energy. This systematic review gives insight into this research field by classifying the existing photocatalyst-enzyme hybrid systems into three sections based on different hybridizing modes between photo- and enzymatic catalysis. Furthermore, existing challenges and proposed strategies are discussed within this context. The first system summarised is the cofactor-mediated hybrid system, in which natural/artificial cofactors act as reducing equivalents that connect photocatalysts with enzymes for light-driven enzymatic biotransformation. Second, the direct contact-based photocatalyst-enzyme hybrid systems are described, including two different kinds of electron exchange sites on the enzyme molecules. Third, some cases where photocatalysts and enzymes are integrated into a reaction cascade with specific intermediates will be discussed in the following chapter. Finally, we provide perspective concerning the future of this field.

Product Inhibition and the Catalytic Destruction of a Nerve Agent Simulant by Zirconium-Based Metal-Organic Frameworks

Rapid degradation/destruction of chemical warfare agents, especially ones containing a phosphorous-fluorine bond, is of notable interest due to their extreme toxicity and typically rapid rate of human incapacitation. Recent studies of the hydrolytic destruction of a key nerve agent simulant, dimethyl 4-nitrophenylphosphate (DMNP), catalyzed by Zr₆-based metal-organic frameworks (MOFs), have suggested deactivation of the active sites due to inhibition by the products as the reaction progresses. In this study, the interactions of two MOFs, NU-1000 and MOF-808, and two hydrolysis products, dimethyl phosphate (DMP) and ethyl methyl phosphonate (EMP), from the hydrolysis of the simulant (DMNP) and nerve agent ethyl methylphosphonofluoridate (EMPF), resembling the hydrolysis degradation product of the G-series nerve agent, Sarin (GB), have been investigated to deconvolute the effect of product inhibition from other effects on catalytic activity. Kinetic studies via in situ nuclear magnetic resonance spectroscopy indicated substantial product inhibition upon catalyst activity after several tens to several thousand turnovers, depending on specific conditions. Apparent product binding constants were obtained by fitting initial reaction rates at pH 7.0 and pH 10.5 to a Langmuir-Freundlich binding/adsorption model. For the fits, varying amounts/concentrations of candidate inhibitors were introduced before the start of catalytic hydrolysis. The derived binding constants proved suitable for quantitatively describing product inhibition effects upon reaction rates over the extended time course of simulant hydrolysis by aqua-ligand-bearing hexa-zirconium(IV) nodes.

Isomer of linker for NU-1000 yields a new she-type, catalytic, and hierarchically porous, Zr-based metal-organic framework

The well-known MOF (metal-organic framework) linker tetrakis(p-benzoate)pyrene (TBAPy^4-) lacks steric hindrance between its benzoates. Changing the 1,3,6,8-siting of benzoates in TBAPy^4- to 4,5,9,10-siting introduces substantial steric hindrance and, in turn, enables the synthesis of a new hierarchically porous, she-type MOF Zr₆(μ₃-O)₄(μ₃-OH)₄(C₆H₅COO)₃(COO)₃(TBAPy-2)_3/2 (NU-601), where TBAPy-2^4- is the 4,5,9,10 isomer of TBAPy^4-. NU-601 shows high catalytic activity for degradative hydrolysis of a simulant for G-type fluoro-phosphorus nerve agents.

A historical perspective on porphyrin-based metal-organic frameworks and their applications

Porphyrins are important molecules widely found in nature in the form of enzyme active sites and visible light absorption units. Recent interest in using these functional molecules as building blocks for the construction of metal-organic frameworks (MOFs) have rapidly increased due to the ease in which the locations of, and the distances between, the porphyrin units can be controlled in these porous crystalline materials. Porphyrin-based MOFs with atomically precise structures provide an ideal platform for the investigation of their structure-function relationships in the solid state without compromising accessibility to the inherent properties of the porphyrin building blocks. This review will provide a historical overview of the development and applications of porphyrin-based MOFs from early studies focused on design and structures, to recent efforts on their utilization in biomimetic catalysis, photocatalysis, electrocatalysis, sensing, and biomedical applications.

Exploration of artemisinin derivatives and synthetic peroxides in antimalarial drug discovery research

Malaria is a life-threatening infectious disease caused by protozoal parasites belonging to the genus Plasmodium. It caused an estimated 405,000 deaths and 228 million malaria cases globally in 2018 as per the World Malaria Report released by World Health Organization (WHO) in 2019. Artemisinin (ART), a "Nobel medicine" and its derivatives have proven potential application in antimalarial drug discovery programs. In this review, antimalarial activity of the most active artemisinin derivatives modified at C-10/C-11/C-16/C-6 positions and synthetic peroxides (endoperoxides, 1,2,4-trioxolanes, 1,2,4-trioxanes, and 1,2,4,5-tetraoxanes) are systematically summarized. The developmental trend of ART derivatives, and cyclic peroxides along with their antimalarial activity and how the activity is affected by structural variations on different sites of the compounds are discussed. This compilation would be very useful towards scaffold hopping aimed at avoiding the unnecessary complexity in cyclic peroxides, and ultimately act as a handy resource for the development of potential chemotherapeutics against Plasmodium species.

Bifunctional metal–organic frameworks for the hydrogenation of nitrophenol using methanol as the hydrogen source

This work reports the reduction of 4-nitrophenol to 4-aminophenol using UiO-66(Zr) as a bifunctional photocatalyst and hydrogenation catalyst using methanol as the hydrogen source.

Biocompatibility and biodegradability of metal organic frameworks for biomedical applications

Metal organic frameworks (MOFs) are a unique class of smart hybrid materials that have recently attracted significant interest for catalysis, separation and biomedical applications. Different strategies have been developed to overcome the limitations of MOFs for bio-applications in order to produce a system with high biocompatibility and biodegradability. In this review, we outline the chemical and physical factors that dictate the biocompatibility and biodegradability characteristics of MOFs including the nature of the metal ions and organic ligands, size, surface properties and colloidal stability. This review includes the in vitro biodegradation and in vivo biodistribution studies of MOFs to better understand their pharmacokinetics, organ toxicity and immune response. Such studies can guide the design of future bio-friendly systems that bring us closer to safely translating these platforms into the pharmaceutical consumer market.

Porphyrin-based frameworks for oxygen electrocatalysis and catalytic reduction of carbon dioxide

The recent progress made on porphyrin-based frameworks and their applications in energy-related conversion technologies (e.g., ORR, OER and CO₂RR) and storage technologies (e.g., Zn–air batteries).

Creation of discrete active site domains via mesoporous silica poly(styrene) composite materials for incompatible acid–base cascade reactions

Mesoporous silica/polymer hybrid materials catalyze a two-step acid and base cascade reaction. Catalyst design emphasizes compartmentalization of incompatible Lewis base and Brønsted acid catalysts by tuning polymer chain length and silica pore diameter.meter.

Ultrasensitive, rapid and selective sensing of hazardous fluoride ion in aqueous solution using a zirconium porphyrinic luminescent metal-organic framework

The development of a rapid and sensitive method for the detection of fluoride ion (F^-) in aqueous systems is of great significance for human health and environmental monitoring. In this study, a zirconium porphyrinic luminescent metal-organic framework (LMOF), PCN-222, was employed as a novel fluorescent probe for the ultrasensitive, rapid and selective detection of F^- in water. The PCN-222 probe was prepared by a facile solvothermal method. It exhibited good fluorescence stability and was highly stable in water. The fluorescence emission of PCN-222 could be effectively and selectively quenched by F^- due to the strong coordination affinity of F^- to the zirconium clusters in PCN-222. The proposed fluorescence method for F^- detection based on PCN-222 probe afforded a linear response range of 1-20 μmol/L and a very low detection limit (0.048-0.065 μmol/L) in reference to many reported F^- fluorescent probes. Moreover, a rapid response time (<10 s) was obtained due to the open and uniform pore structure of PCN-222 that allowed the fast diffusion of F^- to interact with the zirconium recognition sites. Finally, the PCN-222 probe was successfully applied for the fluorescence detection of F^- in real water samples. These results highlight the great application potential of LMOF in the sensing fields.

Water and Metal-Organic Frameworks: From Interaction toward Utilization

The steep stepwise uptake of water vapor and easy release at low relative pressures and moderate temperatures together with high working capacities make metal-organic frameworks (MOFs) attractive, promising materials for energy efficient applications in adsorption devices for humidity control (evaporation and condensation processes) and heat reallocation (heating and cooling) by utilizing water as benign sorptive and low-grade renewable or waste heat. Emerging MOF-based process applications covered are desiccation, heat pumps/chillers, water harvesting, air conditioning, and desalination. Governing parameters of the intrinsic sorption properties and stability under humid conditions and cyclic operation are identified. Transport of mass and heat in MOF structures, at least as important, is still an underexposed topic. Essential engineering elements of operation and implementation are presented. An update on stability of MOFs in water vapor and liquid systems is provided, and a suite of 18 MOFs are identified for selective use in heat pumps and chillers, while several can be used for air conditioning, water harvesting, and desalination. Most applications with MOFs are still in an exploratory state. An outlook is given for further R&D to realize these applications, providing essential kinetic parameters, performing smart engineering in the design of systems, and conceptual process designs to benchmark them against existing technologies. A concerted effort bridging chemistry, materials science, and engineering is required.

Oxygen-Vacancy-Enhanced Singlet Oxygen Production for Selective Photocatalytic Oxidation

Oxygen vacancies are usually thought to be beneficial for photogenerated charge separation. In this work, the oxygen vacancies in ov-Bi₂ O₃ (Bi₂ O₃ with oxygen vacancy) were found to be able to produce ¹ O₂ in the dark owing to chemical adsorption. The oxygen vacancies were further found to be responsible for ov-Bi₂ O₃ exhibiting higher ¹ O₂ generation under light irradiation with ¹ O₂ as the only reactive oxygen species (ROS) than Bi₂ O₃ with ¹ O₂ , H₂ O₂ , and others as the ROS. The photocatalytic activity was investigated for the selective photo-oxidation of phenyl methyl sulfide to phenyl methyl sulfoxide and phenyl alcohol to benzaldehyde. In either case, ov-Bi₂ O₃ displayed better performance than Bi₂ O₃ , suggesting the significant role of oxygen vacancies in modulating the photocatalytic oxidation properties. This work provides an alternative approach to obtain singlet oxygen, which may guide further design of photocatalysts with high efficiency and selectivity towards photocatalytic organic synthesis.

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

In this review we present relevant and recent applications of porphyrin derivatives as photocatalysts in organic synthesis, involving both single electron transfer (SET) and energy transfer (ET) mechanistic approaches. We demonstrate that these highly conjugated photosensitizers show increasing potential in photocatalysis since they combine both photo- and electrochemical properties which can substitute available metalloorganic photocatalysts. Batch and continuous-flow approaches are presented highlighting the relevance of enabling technologies for the renewal of porphyrin applications in photocatalysis. Finally, the reaction scale in which the methodologies were developed are highlighted since this is an important parameter in the authors' opinion.

Combining enyne metathesis with long-established organic transformations: a powerful strategy for the sustainable synthesis of bioactive molecules

This account surveys the current progress on the application of intra- and intermolecular enyne metathesis as main key steps in the synthesis of challenging structural motifs and stereochemistries found in bioactive compounds. Special emphasis is placed on ruthenium catalysts as promoters of enyne metathesis to build the desired 1,3-dienic units. The advantageous association of this approach with name reactions like Grignard, Wittig, Diels–Alder, Suzuki–Miyaura, Heck cross-coupling, etc. is illustrated. Examples unveil the generality of such tandem reactions in providing not only the intricate structures of known, in vivo effective substances but also for designing chemically modified analogs as valid alternatives for further therapeutic agents.

Determination of the dehydration pathway in a flexible metal-organic framework by dynamic in situ x-ray diffraction

Understanding guest exchange processes in metal-organic frameworks is an important step toward the rational design of functional materials with tailor-made properties. The dehydration of the flexible metal-organic framework [Co(AIP)(bpy)0.5(H2O)]•2H2O was studied by novel in situ dynamic x-ray diffraction techniques. The complex mechanism of dehydration, along with the as-yet unreported metastable structures, was determined. The structural information obtained by the application of these techniques helps to elucidate the important guest-host interactions involved in shaping the structural landscape of the framework lattice and to highlight the importance of utilizing this technique in the characterization of functional framework materials.

Cross-Linked Surface Engineering to Improve Iron Porphyrin Catalytic Activity

Quasi-two-dimensional (QTD) structural heterogeneous catalysts have attracted a broad interest in multidisciplinary research due to their unique structure, preeminent surface properties and outstanding catalytic performance. Herein, a HZIF@TCPP-Fe/Fe heterogeneous catalyst based on cross-linked surface engineering is constructed by supporting QTD TCPP-Fe/Fe ultra-thin metallized film (≈2 nm) on hollow skeleton of zeolite imidazolate frameworks. The designed QTD structure exhibits high efficiency for the catalytic oxidative dehydrogenation of aromatic hydrazides reactions which is the key technology in various industrial processes. Taking advantage of QTD structure with excellent accessibility, the metallized film with irregular defects not only enhances electron transfer during the reaction but also exposes more surface-active sites. Furthermore, the prepared HZIF@TCPP-Fe/Fe heterogeneous catalyst can be recycled and reused, which is of great significance in the field of green chemistry.