Turning on Visible-Light Photocatalytic C-H Oxidation over Metal-Organic Frameworks by Introducing Metal-to-Cluster Charge Transfer

Trapping effect of surface deficient cocrystal synergizes with bimetallic nanoparticles against bacterial infection in wounds

Metal nanoparticles exert broad-spectrum antimicrobial effects through in situ generation of reactive oxygen species (ROS). However, the limited penetrability of ROS restricts the scope of antimicrobial activity of these nanoparticles. Herein, we develop core-shell nanoparticles composed of a surface-defective cocrystal shell and a Cu/Zn bimetallic core. Surface defects are generated by etching myricetin from a berberine-dihydromyricetin cocrystal, and bacterial adsorption efficiency peaks when the cocrystal contains 40 % myricetin. Similarly, Cu2+ doping on the surface of Zn nanoparticles to form a bimetallic core can optimize the ROS generation efficiency by facilitating effective electron transfer. Nanoparticles with this combined core-shell structure not only capture bacteria effectively but also draw bacteria into the ROS-killing range of the metal particles, thereby enhancing activity against drug-resistant bacteria. The feasibility of antibacterial infection was further validated in wounds of mice infected with Escherichia coli and Staphylococcus aureus. This strategy could be used to optimize antimicrobial nanoparticles with ROS-generating functionality and could have an impact on combating bacterial resistance.

Visible-Light-Driven Benzylic C-H Oxidation Catalyzed by Bisphosphonium Salt

An efficient photocatalytic method for the synthesis of carbonyl compounds through the oxidation of benzyl C-H bonds was developed. A series of acetophenone derivatives were successfully synthesized by utilizing a bisphosphonium salt catalyst and molecular oxygen as the oxidant. Preliminary mechanistic studies indicated that the reaction mechanism involved a free-radical pathway.

Defective Metal-Organic Frameworks Confined PdO with High Resistance to Reduction: An Efficient Photocatalyst for Hydrodeoxygenation of Lignin Derivatives

The positively charged metal species in the supported catalyst is often highly active in various reactions, and stabilization of this state is vital for fabricating catalysts with long-term cycles, particularly under reducing reaction conditions. Herein, we propose a strategy to fabricate reduction-resistant PdO by constructing enhanced metal-support interaction (MSI) using subnanometer nodes in defective metal-organic framework (MOF). Specifically, a photo-induced way was developed to generate defected Zr6O8 nodes for enhanced MSI in nanoconfined space. The obtained Pd/defective-MOF composites not only stabilize PdO via an unsaturated Zr6O8 cluster for a long period under photoreducing conditions but also provide a driving force for substrate enrichment and proton transfer by -OH/-OH2 coordination, leading to a dramatically enhanced catalytic performance in the photocatalytic hydrodeoxygenation of lignin derivatives, which is 4.5 times that of Pd/ideal-MOF composites with weak MSI. This work provides ideas for the selection of ultrasmall support to stabilize positively charged metal and also an avenue to design photocatalysts with tightly connected heterogeneous in MOFs.

Electro-oxidation of lincomycin and human pathogenic bacteria using carbon-supported lanthanide derivatives anodes: Accelerating wastewater remediation

Lanthanide metal-organic framework derivatives (Ln-MOFs) have emerged as effective conductive catalysts for enhancing the electrochemical performance of electrodes. This study presents a strategic approach to significantly improve the electrocatalytic activity of an anode in electrooxidation by integrating high-valence lanthanide metals into a carboxymethyl-functionalized carbon substrate. The focus is on investigating the degradation property of lincomycin (LIN) and the inactivation of human pathogenic bacteria (HPB, Escherichia coli (E. coli)). The results demonstrated that the Sm-MOF carboxymethyl-functionalized derived carbon (Sm-MOF/MCF) electrode exhibited exceptional electrochemical properties, including minimal charge transfer resistance (97.613 Ω/cm2), low corrosion current density (1.213 × 10-5 mA/cm2), high carrier density (2.071 × 1032), and an electrochemically active area of 229.600 cm2. As a promising anode, Sm-MOF/MCF achieved 99 % removal of LIN within 60 min and 95 % inactivation of E. coli within 20 min. Notably, density functional theory (DFT) calculations revealed that doping with Sm-MOF derivatives significantly reduced the activation energy barrier for hydroxyl radical (·OH) formation, thereby facilitating its generation and subsequent reaction with LIN and E. coli. In brief, this work offers innovative strategies for the development of electrodes aimed at effectively removing LIN and inactivating harmful HPB, highlighting new avenues for environmental remediation.

Advanced Alkali Metal Batteries Based on MOFs and Their Composites

The integration of metal-organic frameworks (MOFs) with functional materials has established a versatile platform for a wide range of energy storage applications. Due to their large specific surface area, high porosity, and tunable structural properties, MOFs hold significant promise as components in energy storage systems, including electrodes, electrolytes, and separators for alkali metal-ion batteries (AIBs). Although lithium-ion batteries (LIBs) are widely used, their commercial graphite anode materials are nearing their theoretical capacity limits, and the scarcity of lithium and cobalt resources increases costs. Although zinc-ion batteries (ZIBs) suffer from limited cycling stability, they are attractive for their low cost, high capacity, and excellent safety. Meanwhile, potassium-ion (PIBs) and sodium-ion batteries (SIBs) show promise due to their affordability and abundant resources, but they encounter issues such as short cycle life and low energy density. This review outlines the applications of MOF composites in LIBs, SIBs, and ZIBs, introduces common synthesis methods, and forecasts future development directions and challenges in energy storage applications. We emphasize how the understanding can lay the foundation for developing MOF composites with enhanced functionalities.

Effective Hole Utilization for Atomically Dispersed Low-Coordination Molybdenum Accelerating Photocatalytic C─H Activation

Photocatalytic acceptorless dehydrogenation of alcohols offers a promising strategy to produce the corresponding carbonyl compounds and clean fuel H2. However, the sluggish kinetics of the alkoxy C─H bond cleavage attributes to the inefficient utilization of photogenerated holes greatly restricts the photocatalytic activity. Here we develmically dispersed low-coordination Mo on ultrathin ZnIn2S4 nanosheets that can greatly accelerate photocatalytic C─H activation. An internal quantum efficiency of 45.2% at 400 nm together with 99% benzaldehyde (BAD) selectivity is achieved using benzyl alcohol (BA) as a model substrate. Extensive experimental characterizations and theoretical calculations reveal that the low-coordination Mo tunes the local atomic configuration of highest occupied molecular orbital to trap holes produced under photoexcitation within picoseconds. Moreover, the incorporated site-specific Mo greatly improves the lifetime and diffusion length of photogenerated holes and optimizes the driving force of alkoxy C─H activation, which are responsible for the excellent performance. This work marks a significant stride to enhance the utilization efficiency of holes for promoting photocatalytic C─H activation.

Enhanced Oxidative Coupling of Thiols to Disulfides Using the Visible-Light-Responsive POM@MOF Constructed with Ru Metalloligands

The photocatalytic oxidative coupling of thiols to disulfides by using visible light represents an economically viable and environmentally sustainable strategy. A novel POM@MOF photocatalyst (Ru-CdS-SiW) was synthesized through the encapsulation of Keggin-type [SiW12O40]4- within a MOF composed of Ru metalloligands and {Cd4S2O16} clusters. In this structure, the incorporation of POMs to the MOFs reduced the charge transport distance, facilitated the separation and transfer of photogenerated charges and holes, and prevented the recombination of electron-hole pairs. The Ru-CdS-SiW catalyst demonstrated exceptional catalytic performance, achieving a 98.1% yield in the S-S bond formation from 4-methylthiophenol coupling with an apparent quantum yield of 4.8% at 440 nm. Through comprehensive exploratory experiments and electron paramagnetic resonance (EPR) measurements, we elucidated the mechanism underlying the photoinduced oxidative coupling of thiols. Notably, this catalytic reaction operates under mild visible-light conditions and exhibits remarkable recyclability, presenting significant potential for applications in sensitive systems, such as protein disulfide bond formation.

Post-Modification of MOF with Electron Donor for Efficient Photocatalytic Oxidative Organic Transformations

Construction of donor-accepter systems via self-assembling electron donor and acceptor chromophores within one single metal-organic framework (MOF) for advanced artificial photosynthesis is of great intertest yet a major challenge. Herein, an electron donor porphyrin 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin (PCOOH) was successfully integrated into a highly stable and porous electron acceptor naphthalene diimide (NDI)-based MOF (Zr-NDI) through the postmodified approach of solvent-assisted ligand incorporation (SALI). Benefiting from the efficient photoinduced electron transfer (PET) from the donor PCOOH anchored on the Zr-nodes to the acceptor NDI ligand, which contributes to the abundant generation of reactive oxygen species (ROS) of superoxide radical (O2 •-), the resulting MOF Zr-NDI-PCOOH exhibited superior photocatalytic activities that among the highest levels of MOF-based photocatalysts to aerobic oxidation reactions, including hydroxylation of arylboronic acids and homocoupling of amines. This work exemplifies an avenue to develop high-efficiency MOF-based donor-acceptor systems for advanced artificial photosynthesis through facile post-modified approach.

In situ growth of bismuth oxybromide/bismuth molybdate 2D/2D Z-scheme heterojunctions with rich interfacial oxygen vacancies for photocatalytic benzylic C(sp3)-H bond activation

The selective oxidation of toluene into valuable chemicals via photocatalytic C(sp3)-H bond activation represents a significant, yet challenging process. Here, the in situ construction of bismuth oxybromide/bismuth molybdate (BiOBr/Bi2MoO6) 2D/2D Z-scheme heterojunctions featuring interface-induced oxygen vacancies (OVs) is introduced. The optimized BiOBr/Bi2MoO6 sample has a remarkable yield rate of benzaldehyde at 2134.28 μmol g-1 h-1 under blue LED irradiation, surpassing the performance of BiOBr and Bi2MoO6 by 8.1 and 2.9 times, respectively. Insights from density functional theory (DFT) calculations, electron paramagnetic resonance (EPR), and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies highlight the critical role of the Z-scheme electronic configuration and OVs in attaining the superior photocatalytic toluene conversion efficiency. This study advances the photocatalytic conversion of benzaldehyde within an OV-enhanced direct Z-scheme system, facilitating the activation of inert C(sp3)-H bonds, and contributes to the development of high-performance catalysts for sustainable chemical processes.

Combination of FeII-O Species and Fe-O-Zr Bonds Empowers FeOx Nanoclusters Anchored on UiO-66 Robust H2S-Selective Catalytic Oxidation Performance

The low sulfur selectivity of Fe-based H2S-selective catalytic oxidation catalysts is still a problem, especially at a high O2 content. This is alleviated here through anchoring FeOx nanoclusters on UiO-66 via the formation of Fe-O-Zr bonds. The introduced FeOx species exist in the form of FeIII and FeII. Therein the FeIII-O species are the predominant active sites for H2S-oxidation. The formed Fe-O-Zr bonds strengthen the redox cycle of FeIII/FeII through promoting electron transfer from Fe to Zr. The FeII-O species can activate molecular oxygen to oxidize H2S into elemental S, which accelerates the formation rate of atomic S, hindering its further oxidation into SO2. The combination of these factors empowers the catalysts, enabling 100% H2S conversion and 98.2% sulfur yield. The catalyst also has satisfactory stability with the sulfur selectivity only decreasing from 98.2% to 91.3% after the reaction going on 50 h. The decreased sulfur selectivity might be caused by the deterioration of pores and the deposition of elemental S on the surface. The former hinders the diffusion of sulfur oligomers timely from pores to the gas phase, while the latter is suspected to capture electrons to promote its further reaction with molecular oxygen.

Cu-UiO-66 Catalyzed Synthesis of Imines via Acceptorless Dehydrogenative Coupling of Alcohols and Amines

Herein, the Cu-UiO-66 catalyst was developed for acceptorless dehydrogenative coupling (ADC) between alcohols and amines to produce imines. The Cu-UiO-66 catalyst was synthesized by installing Cu2+ onto Zr-oxo clusters in UiO-66, and the catalyst efficiently catalyzes the ADC reaction under mild and environmentally friendly conditions with excellent selectivity. Mechanistic studies reveal that the O2⋅- radicals and porosity of formed in Cu-UiO-66 participate cooperatively during the catalytic cycle. Meanwhile, the only by-product of the system is environmentally benign water. Cycling tests and hot filtration tests showed that the Cu-UiO-66 catalyst exhibited excellent stability and catalytic activity during the reaction. Importantly, the Cu-UiO-66 catalyst might provide a promising strategy for the ADC reaction between alcohols and amines to produce imines.

Location-Specific Microenvironment Modulation Around Single-Atom Metal Sites in Metal-Organic Frameworks for Boosting Catalysis

Despite coordination environment of catalytic metal sites has been recognized to be of great importance in single-atom catalysts (SACs), a significant challenge remains in the understanding how the location-specific microenvironment in the higher coordination sphere influences their catalysis. Herein, a series of Cu-based SACs, namely Cu1/UiO-66-X (X=-NO2, -H, and -NH2), are successfully constructed by anchoring single Cu atoms onto the Zr-oxo clusters of metal-organic frameworks (MOFs), i.e., UiO-66-X. The -X functional groups dangling on the MOF linkers could be regarded as location-specific remote microenvironment to regulate electronic properties of the single Cu atoms. Remarkably, they exhibit significant differences in the catalysis toward the hydroboration of alkynes. The activity follows the order of Cu1/UiO-66-NO2 > Cu1/UiO-66 > Cu1/UiO-66-NH2 under identical reaction conditions, where Cu1/UiO-66-NO2 showcases the phenylacetylene conversion of 92 %, ~3.5 times higher efficiency than that of Cu1/UiO-66-NH2. Experimental and calculation results jointly support that the Cu electronic structure is modulated by the location-specific microenvironment, thereby regulating the product desorption and promoting the catalysis.

Constructing an Isopolymolybdate-Based Bifunctional Photocatalyst for Promoting Nitroaromatic Reduction and C-H Oxidation

Amide compounds are widely present in drug molecules and natural products, which can be synthesized by acid-amine condensation. It is urgent to design new photocatalysts for achieving both nitroaromatic reduction and C-H oxidation to obtain raw materials, carboxylic acids, and aromatic amines. Herein, a novel isopolymolybdate-incorporated photoactive metal-organic framework, NiMo12-TPT, was constructed by combining the oxidation catalyst [Mo12O40]8-, Ni(II) cation, and photosensitive ligand 2,4,6-tri(4-pyridyl)-1,3,5-triazine (TPT). In the structure, the superior electron storage capacity of [Mo12O40]8-, with its multiple metal centers containing d-electrons, is conducive to providing electrons for the reduction of nitrobenzenes. The donor-acceptor structure of the TPT facilitates the separation of intramolecular charges. Furthermore, the π···π interactions between the TPT molecules promote the transfer of electrons and enhance the performance of photocatalysis. Under illumination, NiMo12-TPT can activate the C-H bonds to generate carboxylic acids with excellent selectivity and simultaneously realize the multistep proton-coupled electron transfer (PCET) process for nitroaromatic reduction. Moreover, EPR tests and the quenching experiments indicated that •O2- is the main reactive oxygen species (ROS) in the photocatalytic redox reaction process.

Selective Photocatalytic C─H Oxidation Using All-Inorganic Perovskite Quantum Dots Encapsulated in UiO-Series MOFs

All-inorganic cesium lead halide (CsPbX3, X = Cl, Br, I) perovskite quantum dots (PeQDs) are successfully incorporated within the cages of zirconium-based UiO-series metal-organic frameworks (MOFs) using in situ ship-in-a-bottle method at room temperature under ambient conditions. The resulting mBPP-MOF, which includes the 4,4'-(2,2'-bipyridyl-5,5'-diyl)dibenzoic acid (H2BPP) linker, features a larger cavity size than UiO-66 and UiO-67-bpy, allowing for uniform accommodation of PeQDs within its cages. This PeQDs@MOF hybrid heterostructure enhances the separation and transfer of photogenerated charges, enabling the synthesized CsPbBr3@mBPP-MOF to demonstrate highly selective and stable performance in the photocatalytic oxidation of toluene under visible light irradiation at 395 nm. This advancement represents a potential breakthrough in organic photocatalysis due to the material's low cost, ease of processing, high efficiency, and tunable bandgap.

Investigation into the Internal Factors for the Catalytic Oxidation of Cyclohexane by Zr(IV)-Based Metal-Organic Frameworks

Three porous Zr(IV)-based MOFs, UiO-66, MOF-808 and MOF-802, were selected to catalyze cyclohexane oxidation in order to reveal the intrinsic factors of the active site and catalytic performance. It was found that reducing the number of Zr6O8 ligand linkages could improve the catalytic efficiency of cyclohexane oxidation. The main reason for this is the different enrichment abilities of MOFs with different linkage numbers for cyclohexane, which was confirmed by the TPD of cyclohexane and also by GCMC simulations. Meanwhile, the catalytic effect of MOF-802 was lower than expected due to its low porosity and narrow inner pore size. The by-products were identified in detail by GC-MS, providing evidence for this catalytic mechanism. In addition, the potential of this catalyst for industrial applications in cyclohexane oxidation was demonstrated by optimizing the catalytic conditions.

Energy transfer-mediated multiphoton synergistic excitation for selective C(sp3)-H functionalization with coordination polymer

Activation and selective oxidation of inert C(sp3)-H bonds remain one of the most challenging tasks in current synthetic chemistry due to the inherent inertness of C(sp3)-H bonds. In this study, inspired by natural monooxygenases, we developed a coordination polymer with naphthalenediimide (NDI)-based ligands and binuclear iron nodes. The mixed-valence FeIIIFeII species and chlorine radicals (Cl•) are generated via ligand-to-metal charge transfer (LMCT) between FeIII and chlorine ions. These Cl• radicals abstract a hydrogen atom from the inert C(sp3)-H bond of alkanes via hydrogen atom transfer (HAT). In addition, NDI converts oxygen to 1O2 via energy transfer (EnT), which then coordinates to FeII, forming an FeIV = O intermediate for the selective oxidation of C(sp3)-H bonds. This synthetic platform, which combines photoinduced EnT, LMCT and HAT, provides a EnT-mediated parallel multiphoton excitation strategy with kinetic synergy effect for selective C(sp3)-H oxidation under mild conditions and a blueprint for designing coordination polymer-based photocatalysts for C(sp3)-H bond oxidation.

Photocatalytic Selective Oxidation of Toluene over Chlorine-Coordinated MIL-101(Fe) under Ambient Conditions

The activation of an inert C(sp3)-H bond in selective oxidation of hydrocarbons under mild conditions is a critical and challenging process. Herein, we report a stable chlorine-coordinated metal-organic framework (MOF) photocatalyst, MIL-101(Fe), for efficient visible-light-driven photocatalytic selective oxidation of toluene to benzaldehyde in air under ambient conditions. Encouragingly, a benzaldehyde formation yield of 3.11 mmol·g-1·h-1 with a selectivity of 92.1% is achieved in 5 h, which is superior to most of the reported works. Based on the experimental results and characterizations, the high catalytic performance is mainly due to the promoted rate-limiting step of C(sp3)-H bond activation by a chlorine radical (Cl·) from the coordinated -Cl in the MIL-101(Fe) structure. In addition, the present photocatalyst possesses good substrate tolerance for photocatalytic selective oxidation of various toluene derivatives under optimized conditions.

Hydrogen Peroxide Heterolytic Cleavage Induced Gas Phase Photo-Fenton Oxidation of Nitric Oxide

Nitric oxide (NO) is one of the major air pollutants that may cause ecological imbalance and severe human disease. However, the removal of NO faces challenges of low efficiency, high energy consumption, and production of toxic NO2 byproducts. Herein, we report an efficient *OOH intermediate-involved NO oxidation route with high NO3- selectivity via a gas phase photo-Fenton system. Fe single atoms (Fe SAs)-anchored NH2-UiO-66(Zr) (Fe SAs@NU) was synthesized. The five-coordinated Fe SAs undergo a transient structure reconstitution during the photo-Fenton process, which enables a novel heterolytic cleavage pathway of H2O2 to derive specific ·OOH/·O2- radicals as reactive oxygen species. Therefore, a high NO (550 parts per billion) removal rate of 81% (NO3- selectivity up to 99%) is achieved under visible-light irradiation (>420 nm). This study provides new insight for the high-performance photo-Fenton process via a transient structure reconstitution pathway for the removal of gas phase NOx pollutants.

Polymer-Supported Pd Nanoparticles for Solvent-Free Hydrogenation

Breaking the trade-off between activity and stability of supported metal catalysts has been a long-standing challenge in catalysis, especially for metal nanoparticles (NPs) with high hydrogenation activity but poor stability. Herein, we report a porous poly(divinylbenzene) polymer-supported Pd NP catalyst (Pd/PDVB) with both high activity and excellent stability for the solvent-free hydrogenation of nitrobenzene, even at ambient temperature (25 °C) and H2 pressure (0.1 MPa). Pd/PDVB gave a turnover frequency as high as 22,632 h-1 at 70 °C and 0.4 MPa, exceeding 5556 h-1 of the classical Pd/C catalyst under equivalent conditions. Mechanistic studies reveal that the polymer support benefits the desorption of the aniline product from the Pd surface, which is crucial for rapid hydrogenation under solvent-free conditions. In addition, the polymer support in Pd/PDVB efficiently hindered Pd leaching, resulting in good stability.

Metal-organic frameworks for organic transformations by photocatalysis and photothermal catalysis

Organic transformation by light-driven catalysis, especially, photocatalysis and photothermal catalysis, denoted as photo(thermal) catalysis, is an efficient, green, and economical route to produce value-added compounds. In recent years, owing to their diverse structure types, tunable pore sizes, and abundant active sites, metal-organic framework (MOF)-based photo(thermal) catalysis has attracted broad interest in organic transformations. In this review, we provide a comprehensive and systematic overview of MOF-based photo(thermal) catalysis for organic transformations. First, the general mechanisms, unique advantages, and strategies to improve the performance of MOFs in photo(thermal) catalysis are discussed. Then, outstanding examples of organic transformations over MOF-based photo(thermal) catalysis are introduced according to the reaction type. In addition, several representative advanced characterization techniques used for revealing the charge reaction kinetics and reaction intermediates of MOF-based organic transformations by photo(thermal) catalysis are presented. Finally, the prospects and challenges in this field are proposed. This review aims to inspire the rational design and development of MOF-based materials with improved performance in organic transformations by photocatalysis and photothermal catalysis.

Convenient Size Analysis of Polystyrene Nanoplastics via Regulating the Radiative Transition Efficiency

Developing a convenient method to efficiently determine the size of nanoplastics in the environment is urgent in terms of ecological or human health protection. In this work, a novel strategy for discriminating the size of polystyrene (PS)-based nanoplastics was reported via regulating the radiative transition efficiency of NH2-UIO-66 (NU) with benzoic acid (BA) as the auxiliary ligand. The elaborately doped BA capped the defect sites and triggered nonradiative transition efficiency of NU. As a result, the formed composite (denoted as BA-NU) was more sensitive to interaction among neighboring NU and nanoplastics. The interaction between particles limited the rotation and vibration of the benzene ring within the BA-NU molecule, thus increasing the BA-NU fluorescence. The sensitivity of BA-NU on nanoplastics was well controlled by manipulating the doping contents of BA, leading to precisely tunable physicochemical properties for this structure. Deriving from the exquisitely designed nanostructures, the composite of BA-NU was successfully used to discriminate different size PS as an ultrasensitive turn-on probe. This work highlights the possibility of boosting the detection performance by regulating the main structure with guest molecules at the molecular level.

High-Efficiency Photocatalytic Oxidation of Benzyl Alcohol by NH2-UiO-66-(Indole-2,3-Dione)-Fe

The photocatalytic oxidation of biomass-derived benzyl alcohol provides a promising way for the synthesis of benzoic acid, which is an important intermediate with wide applications. To improve the efficiency of photocatalytic benzyl alcohol oxidation to benzoic acid is of great interest. In this work, we propose the utilization of NH2-UiO-66-ID-Fe catalyst for photocatalytic oxidation of benzyl alcohol to benzoic acid, where NH2-UiO-66 is a typically used metal-organic framework, ID is indole-2,3-dione (ID) that has biocompatibility, light absorption property and can be covalently combined with amino-functionalized substances. The NH2-UiO-66-ID-Fe catalyst exhibits improved light absorption and photo-generated electron-hole separation ability compared with NH2-UiO-66. The photocatalytic performance of NH2-UiO-66-ID-Fe was examined for the oxidation of bio-based benzyl alcohol under mild conditions of air atmosphere, room temperature and no additive or additional oxidant involved. The results show that the conversion of benzyl alcohol and the selectivity to benzoic acid could both reach over 99 % in 6 h, and the generation rate of benzoic acid per gram of catalyst is 3.36 mmol g-1 h-1. The reaction mechanism was detected by radical trapping method and in situ electron paramagnetic resonance. This study presents an efficient and environmentally benign avenue for the synthesis of carboxylic acid compounds.

Modifying Parallel Excitations into One Framework for C(sp3)─H Bond Activation with Energy Combined More Than Two Photons

Natural photosynthesis enzymes utilize energies of several photons for challenging oxidation of water, whereas artificial photo-catalysis typically involves only single-photon excitation. Herein, a multiphoton excitation strategy is reported that combines parallel photo-excitations with a photoinduced electron transfer process for the activation of C(sp3)─H bonds, including methane. The metal-organic framework Fe3-MOF is designed to consolidate 4,4',4″-nitrilotrisbenzoic units for the photoactivation of dioxygen and trinuclear iron clusters as the HAT precursor for photoactivating alkanes. Under visible light irradiation, the dyes and iron clusters absorbed parallel photons simultaneously to reach their excited states, respectively, generating 1O2 via energy transfer and chlorine radical via ligand-to-metal charge transfer. The further excitation of organic dyes leads to the reduction of 1O2 into O2 •- through a photoinduced electron transfer, guaranteeing an extra multiphoton oxygen activation manner. The chlorine radical abstracts a hydrogen atom from alkanes, generating the carbon radical for further oxidation transformation. Accordingly, the total oxidation conversion of alkane utilizing three photoexcitation processes combines the energies of more than two photons. This new platform synergistically combines a consecutive excited photoredox organic dye and a HAT catalyst to combine the energies of more than two photons, providing a promising multiphoton catalysis strategy under energy saving, and high efficiency.

Synthetic Chemistry in Flow: From Photolysis & Homogeneous Photocatalysis to Heterogeneous Photocatalysis

Photocatalytic synthesis of value-added chemicals has gained increasing attention in recent years owing to its versatility in driving many important reactions under ambient conditions. Selective hydrogenation, oxidation, coupling, and halogenation with a high conversion of the reactants have been realized using designed photocatalysts in batch reactors with small volumes at a laboratory scale; however, scaling-up remains a critical challenge due to inefficient utilization of incident light and active sites of the photocatalysts, resulting in poor catalytic performance that hinders its practical applications. Flow systems are considered one of the solutions for practical applications of light-driven reactions and have experienced great success in photolytic and homogeneous photocatalysis, yet their applications in heterogeneous photocatalysis are still under development. In this perspective, we have summarized recent progress in photolytic and photocatalytic synthetic chemistry performed in flow systems from the view of reactor design with a special focus on heterogeneous photocatalysis. The advantages and limitations of different flow systems, as well as some practical considerations of design strategies are discussed.

Overview of the environmental risks of microplastics and their controlled degradation from the perspective of free radicals

Owing to the significant environmental threat posed by microplastics (MPs) of varying properties, MPs research has garnered considerable attention in current academic discourse. Addressing MPs in river-lake water systems, existing studies have seldom systematically revealed the role of free radicals in the aging/degradation process of MPs. Hence, this review aims to first analyze the pollution distribution and environmental risks of MPs in river-lake water systems and to elaborate the crucial role of free radicals in them. After that, the study delves into the advancements in free radical-mediated degradation techniques for MPs, emphasizing the significance of both the generation and elimination of free radicals. Furthermore, a novel approach is proposed to precisely govern the controlled generation of free radicals for MPs' degradation by interfacial modification of the material structure. Hopefully, it will shed valuable insights for the effective control and reduction of MPs in river-lake water systems.

Photocatalytic Hydrogen Peroxide Production by a Mixed Ligand-Functionalized Uranyl-Organic Framework

Hydrogen peroxide (H2O2) production driven by solar energy has received enormous attention due to its high efficiency, low cost, and environmental friendliness characteristics. Searching for new photocatalytic materials for H2O2 production is one of the most important targets. In this work, a new three-dimensional (3D) uranyl-organic framework material was constructed with mixed ligands via a solvothermal reaction and used for photocatalytic H2O2 production. The mixed ligand strategy not only benefits the construction of a 3D uranyl-organic framework but also introduces strong photon absorption groups into the framework. The thiophene and pyridine rings in the framework enhance photon absorption and carrier transfer. In addition, with the assistance of the hydrogen abstraction reaction of uranyl centers, the H2O2 production rate reaches 345 μmol h-1 g-1. This study provides a new blueprint for exploring the artificial photosynthesis of H2O2 through uranium-based metal-organic frameworks.

A Ru-porphyrin metal-organic framework with Mn2+ paddlewheel nodes for the selective oxidation of C(sp3)-H bonds

The activation and selective functionalization of inert C(sp3)-H bonds is fundamental for industrial applications and occupies a very important place in industry, but it remains a great challenge in current synthetic chemistry. In this paper, we report an approach for activating reactive tert-butyl peroxyl radicals by modifying Ru-porphyrin into metal-organic frameworks (MOFs) for the activation of inert C(sp3)-H bonds. Under mild conditions, the Ru-porphyrinyl MOF can activate the peroxyl radical, extracting a hydrogen atom from the inert C(sp3)-H bond. Mn2+ paddlewheels with unsaturated coordination sites were introduced into the MOF, and direct oxidative conversion using environmentally friendly oxygen provides a new pathway to activate the inert C(sp3)-H bond.

Selective oxidation of β-keto ester modulated by the d-band centers in D-A conjugated microporous metallaphotoredox catalysts containing M-salen (MZn, Cu and Co) and triazine monomers

Photocatalytic selective oxidation plays an important role in developing green chemistry. However, it is challenging to design an efficient photocatalyst for controlling the selectivity of photocatalytic oxidation reaction and exploring its detailed mechanism. Here, we synthesized three conjugated microporous polymers (CMPs) with D-A structures, named M-SATE-CMPs (MZn, Cu and Co), with different d-band centers based on different metal centers, resulting in the discrepancy in adsorption and activation capacities for the reactants, which produces the selectivity of β-keto esters being catalyzed into α-hydroperoxide β-keto esters (ROOH) or to α-hydroxyl β-keto esters (ROH). Density functional theory (DFT) calculations also demonstrate that the adsorption and activation capacities of the metal active centers in M-SATE-CMPs (MZn, Cu and Co) for ROOH are the key factors to influence the photocatalytic selective oxidation of β-keto ester. This study provides a promising strategy for designing a metallaphotoredox catalyst whose photocatalytic selectivity depends on the d-band center of metal site in the catalyst.

Building Co16-N3-Based UiO-MOF to Expand Design Parameters for MOF Photosensitization

The construction of secondary building units (SBUs) in versatile metal-organic frameworks (MOFs) represents a promising method for developing multi-functional materials, especially for improving their sensitizing ability. Herein, we developed a dual small molecules auxiliary strategy to construct a high-nuclear transition-metal-based UiO-architecture Co16-MOF-BDC with visible-light-absorbing capacity. Remarkably, the N3 - molecule in hexadecameric cobalt azide SBU offers novel modification sites to precise bonding of strong visible-light-absorbing chromophores via click reaction. The resulting Bodipy@Co16-MOF-BDC exhibits extremely high performance for oxidative coupling benzylamine (~100 % yield) via both energy and electron transfer processes, which is much superior to that of Co16-MOF-BDC (31.5 %) and Carboxyl @Co16-MOF-BDC (37.5 %). Systematic investigations reveal that the advantages of Bodipy@Co16-MOF-BDC in dual light-absorbing channels, robust bonding between Bodipy/Co16 clusters and efficient electron-hole separation can greatly boost photosynthesis. This work provides an ideal molecular platform for synergy between photosensitizing MOFs and chromophores by constructing high-nuclear transition-metal-based SBUs with surface-modifiable small molecules.

Toluene Oxidation: CO2 vs Benzaldehyde: Current Status and Future Perspectives

Toluene is a common and significant volatile organic compound (VOC). Although it finds extensive application in various industrial processes (chemical manufacturing, paint and adhesive production, and as a solvent), it creates a huge environmental impact when emitted freely into the atmosphere. Two solutions were found to mitigate the emission of this pollutant: the total oxidation to CO2 and H2O and the selective oxidation into benzaldehyde. This review discusses the two main alternatives for tackling this problem: converting the toluene into carbon dioxide by total oxidation or into benzaldehyde by selective oxidation. It presents new catalytic advances, new trends, and the advantages and disadvantages of both methods.

Portable electrochemical sensing platform based on amidated GO-MOF and PEDOT:PSS for high-efficient detection of ponceau 4R

A promising electrochemical sensing platform for the detection of ponceau 4R in food has been fabricated based on the carboxylated graphene oxide (GO-COOH), metal-organic framework (MOF) UIO-66-NH2, and poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). To this end GO-COOH was covalently coupled with UIO-66-NH2 through amide reaction, endowing the material (GO-CONH-UIO-66) unique hierarchical pores and high chemical stability and as a result improving the conductivity of MOF and the dispersion of GO. After the addition of PEDOT:PSS into GO-CONH-UIO-66, the continuity and conductivity of the composite (PEDOT:PSS/GO-CONH-UIO-66) have been further enhanced, due to the high conductivity, favorable film-forming, and hydrophilic properties of PEDOT:PSS. Systematic electrochemical experiments confirm that the PEDOT:PSS/GO-CONH-UIO-66/GCE shows satisfactory electrochemical sensing properties towards the detection of ponceau 4R, with a wide linear detection range of 0.01-30 μM, a low limit of detection of 3.33 nM, and a high sensitivity of 0.606 μA μM-1 cm-2. The PEDOT:PSS/GO-CONH-UIO-66 sensing platform was successfully used to detect ponceau 4R in beverage, and the detection results were compared with  high-performance liquid chromatography. As a result, the PEDOT:PSS/GO-CONH-UIO-66 composite shows a promising application prospect for rapid detection of ponceau 4R in food and will play significant role in food safety detection and supervision.

Metalation of metal-organic frameworks: fundamentals and applications

Metalation of metal-organic frameworks (MOFs) has been developed as a prominent strategy for materials functionalization for pore chemistry modulation and property optimization. By introducing exotic metal ions/complexes/nanoparticles onto/into the parent framework, many metallized MOFs have exhibited significantly improved performance in a wide range of applications. In this review, we focus on the research progress in the metalation of metal-organic frameworks during the last five years, spanning the design principles, synthetic strategies, and potential applications. Based on the crystal engineering principles, a minor change in the MOF composition through metalation would lead to leveraged variation of properties. This review starts from the general strategies established for the incorporation of metal species within MOFs, followed by the design principles to graft the desired functionality while maintaining the porosity of frameworks. Facile metalation has contributed a great number of bespoke materials with excellent performance, and we summarize their applications in gas adsorption and separation, heterogeneous catalysis, detection and sensing, and energy storage and conversion. The underlying mechanisms are also investigated by state-of-the-art techniques and analyzed for gaining insight into the structure-property relationships, which would in turn facilitate the further development of design principles. Finally, the current challenges and opportunities in MOF metalation have been discussed, and the promising future directions for customizing the next-generation advanced materials have been outlined as well.

Metal-organic frameworks as candidates for tumor sonodynamic therapy: Designable structures for targeted multifunctional transformation

Sonodynamic therapy (SDT), utilizing ultrasound (US) as the trigger, has gained popularity recently as a therapeutic approach with significant potential for treating various diseases. Metal-organic frameworks (MOFs), characterized by structural flexibility, are prominently emerging in the SDT realm as an innovative type of sonosensitizer, offering functional tunability and biocompatibility. However, due to the inherent limitations of MOFs, such as low reactivity to reactive oxygen species and challenges posed by the complex tumor microenvironment, MOF-based sonosensitizers with singular functions are unable to demonstrate the desired therapeutic efficacy and may pose risks of toxicity, limiting their biological applications to superficial tissues. MOFs generally possess distinctive crystalline structures and properties, and their controlled coordination environments provide a flexible platform for exploring structure-effect relationships and guiding the design and development of MOF-based nanomaterials to unlock their broader potential in biological fields. The primary focus of this paper is to summarize cases involving the modification of different MOF materials and the innovative strategies developed for various complex conditions. The paper outlines the diverse application areas of functionalized MOF-based sonosensitizers in tumor synergistic therapies, highlighting the extensive prospects of SDT. Additionally, challenges confronting SDT are briefly summarized to stimulate increased scientific interest in the practical application of MOFs and the successful clinical translation of SDT. Through these discussions, we strive to foster advancements that lead to early-stage clinical benefits for patients. STATEMENT OF SIGNIFICANCE: 1. An overview for the progresses in SDT explored from a novel and fundamental perspective. 2. Different modification strategies to improve the MOFs-mediated SDT efficacy are provided. 3. Guidelines for the design of multifunctional MOFs-based sonosensitizers are offered. 4. Powerful tumor ablation potential is reflected in SDT-led synergistic therapies. 5. Future challenges in the field of MOFs-based SDT in clinical translation are suggested.

Enhancing the Photocatalytic Activity of Halide Perovskite Cesium Bismuth Bromide/Hydrogen Titanate Heterostructures for Benzyl Alcohol Oxidation

Halide perovskite Cs3Bi2Br9 (CBB) has excellent potential in photocatalysis due to its promising light-harvesting properties. However, its photocatalytic performance might be limited due to the unfavorable charge carrier migration and water-induced properties, which limit the stability and photocatalytic performance. Therefore, we address this constraint in this work by synthesizing a stable halide perovskite heterojunction by introducing hydrogen titanate nanosheets (H2Ti3O7-NS, HTiO-NS). Optimizing the weight % (wt%) of CBB enables synthesizing the optimal CBB/HTiO-NS, CBHTNS heterostructure. The detailed morphology and structure characterization proved that the cubic shape of CBB is anchored on the HTiO-NS surface. The 30 wt% CBB/HTiO-NS-30 (CBHTNS-30) heterojunction showed the highest BnOH photooxidation performance with 98% conversion and 75% benzoic acid (BzA) selectivity at 2 h under blue light irradiation. Detailed optical and photoelectrochemical characterization showed that the incorporating CBB and HTiO-NS widened the range of the visible-light response and improved the ability to separate the photo-induced charge carriers. The presence of HTiO-NS has increased the oxidative properties, possibly by charge separation in the heterojunction, which facilitated the generation of superoxide and hydroxyl radicals. A possible reaction pathway for the photocatalytic oxidation of BnOH to BzH and BzA was also suggested. Furthermore, through scavenger experiments, we found that the photogenerated h+, e- and •O2- play an essential role in the BnOH photooxidation, while the •OH have a minor effect on the reaction. This work may provide a strategy for using HTiO-NS-based photocatalyst to enhance the charge carrier migration and photocatalytic performance of CBB.

Triazine Frameworks for the Photocatalytic Selective Oxidation of Toluene

Investigations into the selective oxidation of inert sp3 C-H bonds using polymer photocatalysts under mild conditions have been limited. Additionally, the structure-activity relationship of photocatalysts often remains insufficiently explored. Here, a series of thiophene-based covalent triazine frameworks (CTFs) are used for the efficient and selective oxidation of hydrocarbons to aldehydes or ketones under ambient aerobic conditions. Spectroscopic methods conducted in situ and density functional theory (DFT) calculations revealed that the sulfur atoms within the thiophene units play a pivotal role as oxidation sites due to the generation of photogenerated holes. The effect of photogenerated holes on photocatalytic toluene oxidation was investigated by varying the length of the spacer in a CTF donor-acceptor based photocatalyst. Furthermore, the manipulation of reactive oxygen species was employed to enhance selectivity by weakening the peroxidative capacity. As an illustrative example, this study successfully demonstrated the synthesis of a precursor of the neurological drug AMG-579 using a photocatalytic protocol.

Enhanced Charge Transfer Process and Photocatalytic Activity over a Phosphonate-based MOF via Amorphization Strategy

Recently, amorphous materials have gained great attention as an emerging kind of functional material, and their characteristics such as isotropy, absence of grain boundaries, and abundant defects are very likely to outrun the disadvantages of crystalline counterparts, such as low conductivity, and ultimately lead to improved charge transfer efficiency. Herein, we investigated the effect of amorphization on the charge transfer process and photocatalytic performance with a phosphonate-based metal-organic framework (FePPA) as the research object. Comprehensive experimental results suggest that compared to crystalline FePPA, amorphous FePPA has more distorted metal nodes, which affects the electron distribution and consequently improves the photogenerated charge separation efficiency. Meanwhile, the distorted metal nodes in amorphous FePPA also greatly promote the adsorption and activation of O2. Hence, amorphous FePPA exhibits a better performance of photocatalytic C(sp3)-H bond activation for selective oxidation of toluene to benzaldehyde. This work illustrates the advantages of amorphous MOFs in the charge transfer process, which is conducive to the further development of high performance MOFs-based photocatalysts.

Designed Synthesis of Fe/Zr Bimetallic Organic Framework to Enhance the Selective Conversion of H2S to Sulfur

The development of stable and effective catalysts to convert toxic H2S into high value-added sulfur is essential for production safety and environmental protection. However, the inherent defects of traditional iron- and zirconium-based catalysts, such as poor activity, high oxygen consumption, and low sulfur selectivity, limit their further developments and applications. Herein, the Fe-Zr bimetallic organic framework FeUIO-66(x) with different cubic morphologies was synthesized via a facile solvothermal method. The results indicate that the introduction of Fe not only increases the specific surface area and weak L-sites of the catalyst without changing its crystal structure, which provides enough reaction space and more active sites for the adsorption and activation of H2S, but also reduces the activation energy of the reaction, significantly promoting the selective oxidation of H2S. As a result, the as-obtained FeUIO-66(1) catalyst exhibits the highest desulfurization activity and superior durability and water resistance stability, and its H2S conversion and sulfur selectivity within 50 h are 100 and 88%, respectively. More importantly, the structure of the catalyst after the desulfurization reaction is consistent with that of the fresh counterpart. The study offers new insights into the development of effective and stable bimetallic catalysts to eliminate H2S and recycle sulfur.

Heterogeneous Photocatalytic Strategies for C(sp3 )-H Activation

Activation of ubiquitous C(sp3 )-H bonds is extremely attractive but remains a great challenge. Heterogeneous photocatalysis offers a promising and sustainable approach for C(sp3 )-H activation and has been fast developing in the past decade. This Minireview focuses on mechanism and strategies for heterogeneous photocatalytic C(sp3 )-H activation. After introducing mechanistic insights, heterogeneous photocatalytic strategies for C(sp3 )-H activation including precise design of active sites, regulation of reactive radical species, improving charge separation and reactor innovations are discussed. In addition, recent advances in C(sp3 )-H activation of hydrocarbons, alcohols, ethers, amines and amides by heterogeneous photocatalysis are summarized. Lastly, challenges and opportunities are outlined to encourage more efforts for the development of this exciting and promising field.

Harmonizing Enzyme-like Cofactors to Boost Nanozyme Catalysis

Engineering isolated metal sites resembling the primary coordination sphere of metallocofactors enables atomically dispersed materials as promising nanozymes. However, most existing nanozymes primarily focus on replicating specific metallocofactors while neglecting other supporting cofactors within active pockets, leading to reduced electron transfer (ET) efficiency and thus inferior catalytic performances. Herein, we report a metal-organic framework UiO-67 nanozyme with atomically dispersed iron sites, which involves multiple tailored enzyme-like nanocofactors that synergistically drive the ET process for enhanced peroxidase-like catalysis. Among them, the linker-coupled atomic iron site plays a critical role in substrate activation, while bare linkers and zirconia nodes facilitate the ET efficiency of intermediates. The synergy of three nanocofactors results in a 4.29-fold enhancement compared with the single effort of isolated metal site-based nanocofactor, holding promise in immunoassay for sensitive detection of chlorpyrifos. This finding opens a new way for designing high-performance nanozymes by harmonizing various nanocofactors at the atomic and molecular scale.

Harnessing the Chemical Functionality of Metal-Organic Frameworks Toward Removal of Aqueous Pollutants

Wastewater treatment has been bestowed with a plethora of materials; among them, metal-organic frameworks (MOFs) are one such kind with exceptional properties. Besides their application in gas adsorption and storage, they are applied in many fields. In orientation toward wastewater treatment, MOFs have been and are being successfully employed to capture a variety of aqueous pollutants, including both organic and inorganic ones. This review sheds light on the postsynthetic modifications (PSMs) performed over MOFs to adsorb and degrade recalcitrant. Modifications performed on the metal nodes and the linkers have been explained with reference to some widely used chemical modifications like alkylation, amination, thiol addition, tandem modifications, and coordinate modifications. The boost in pollutant removal efficacy, reaction rate, adsorption capacity, and selectivity for the modified MOFs is highlighted. The rationale and the robustness of micromotor MOFs, i.e., MOFs with motor activity, and their potential application in the capture of toxic pollutants are also presented for readers. This review also discusses the challenges and future recommendations to be considered in performing PSM over a MOF concerning wastewater treatment.

Recent trends in wastewater treatment by using metal-organic frameworks (MOFs) and their composites: A critical view-point

Respecting the basic need of clean and safe water on earth for every individual, it is necessary to take auspicious steps for waste-water treatment. Recently, metal-organic frameworks (MOFs) are considered as promising material because of their intrinsic features including the porosity and high surface area. Further, structural tunability of MOFs by following the principles of reticular chemistry, the MOFs can be functionalized for the high adsorption performance as well as adsorptive removal of target materials. However, there are still some major concerns associated with MOFs limiting their commercialization as promising adsorbents for waste-water treatment. The cost, toxicity and regenerability are the major issues to be addressed for MOFs to get insightful results. In this article, we have concise the current strategies to enhance the adsorption capacity of MOFs during the water-treatment for the removal of toxic dyes, pharmaceuticals, and heavy metals. Further, we have also discussed the role of metallic nodes, linkers and associated functional groups for effective removal of toxic water pollutants. In addition to conformist overview, we have critically analyzed the MOFs as adsorbents in terms of toxicity, cost and regenerability. These factors are utmost important to address before commercialization of MOFs as adsorbents for water-treatment. Finally, some future perspectives are discussed to give directions for potential research.

Nanoconfinement-triggered oligomerization pathway for efficient removal of phenolic pollutants via a Fenton-like reaction

Heterogeneous Fenton reaction represents one of the most reliable technologies to ensure water safety, but is currently challenged by the sluggish Fe(III) reduction, excessive input of chemicals for organic mineralization, and undesirable carbon emission. Current endeavors to improve the catalytic performance of Fenton reaction are mostly focused on how to accelerate Fe(III) reduction, while the pollutant degradation step is habitually overlooked. Here, we report a nanoconfinement strategy by using graphene aerogel (GA) to support UiO-66-NH2-(Zr) binding atomic Fe(III), which alters the carbon transfer route during phenol removal from kinetically favored ring-opening route to thermodynamically favored oligomerization route. GA nanoconfinement favors the Fe(III) reduction by enriching the reductive intermediates and allows much faster phenol removal than the unconfined analog (by 208 times in terms of first-order rate constant) and highly efficient removal of total organic carbon, i.e., 92.2 ± 3.7% versus 3.6 ± 0.3% in 60 min. Moreover, this oligomerization route reduces the oxidant consumption for phenol removal by more than 95% and carbon emission by 77.9%, compared to the mineralization route in homogeneous Fe2++H2O2 system. Our findings may upgrade the regulatory toolkit for Fenton reactions and provide an alternative carbon transfer route for the removal of aqueous pollutants.

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.

Photocatalytic aerobic oxidation of C(sp3)-H bonds

In modern industries, the aerobic oxidation of C(sp3)-H bonds to achieve the value-added conversion of hydrocarbons requires high temperatures and pressures, which significantly increases energy consumption and capital investment. The development of a light-driven strategy, even under natural sunlight and ambient air, is therefore of great significance. Here we develop a series of hetero-motif molecular junction photocatalysts containing two bifunctional motifs. With these materials, the reduction of O2 and oxidation of C(sp3)-H bonds can be effectively accomplished, thus realizing efficient aerobic oxidation of C(sp3)-H bonds in e.g., toluene and ethylbenzene. Especially for ethylbenzene oxidation reactions, excellent catalytic capacity (861 mmol g cat-1) is observed. In addition to the direct oxidation of C(sp3)-H bonds, CeBTTD-A can also be applied to other types of aerobic oxidation reactions highlighting their potential for industrial applications.

Defects-Induced Single-Atom Anchoring on Metal-Organic Frameworks for High-Efficiency Photocatalytic Nitrogen Reduction

Aiming to improve the photocatalytic activity in N2 fixation to produce ammonia, herein, we proposed a photochemical strategy to fabricate defects, and further deposition of Ru single atoms onto UiO-66 (Zr) framework. Electron-metal-support interactions (EMSI) were built between Ru single atoms and the support via a covalently bonding. EMSI were capable of accelerating charge transfer between Ru SAs and UiO-66, which was favorable for highly-efficiently photocatalytic activity. The photocatalytic production rate of ammonia improved from 4.57 μmol g-1  h-1 to 16.28 μmol g-1  h-1 with the fabrication of defects onto UiO-66, and further to 53.28 μmol g-1  h-1 with Ru-single atoms loading. From the DFT results, it was found that d-orbital electrons of Ru were donated to N2 π✶-antibonding orbital, facilitating the activation of the N≡N triple bond. A distal reaction pathway was probably occurred for the photocatalytic N2 reduction to ammonia on Ru1 /d-UiO-66 (single Ru sites decorated onto the nodes of defective UiO-66), and the first step of hydrogenation of N2 was the reaction determination step. This work shed a light on improving the photocatalytic activity via feasibly anchoring single atoms on MOF, and provided more evidences to understand the reaction mechanism in photocatalytic reduction of N2 .

Heating-induced adsorption promoting the efficient removal of toluene by the metal-organic framework UiO-66 (Zr) under visible light

The removal of indoor/outdoor toluene by photocatalysis has drawn much attention due to its low energy consumption and easy availability. However, light inevitably generates heat, and pollutants desorb from catalysts as the temperature rises, which is not beneficial to degradation. Contrast to the frequently occurred phenomena, we firstly found that the adsorption capacity of UiO-66 (Zr) on toluene increased with increasing temperature as adsorption isotherms and in-situ Fourier transform infrared spectra (in-situ FTIR) showed. The optimum temperature was 30 °C. This stage in which adsorption capacity was positively correlated with temperature was called heating-induced adsorption, which achieved a toluene removal efficiency of 69.6 %. By density functional theory (DFT) calculations and changing the metal centers and organic ligands of UiO-66 (Zr) respectively, we disclosed that the heating-induced adsorption was mainly related to the π-π stacking interaction of MOF ligands and toluene. The analysis of samples before and after adsorption showed that the interaction between UiO-66 (Zr) and adsorbed toluene facilitated the charge transfer and prolonged the carrier lifetime, leading to the increase of hydroxyl radicals (•OH) in photocatalysis. Therefore, a synergistic effect between heating-induced adsorption and photocatalysis was proposed by analyzing the adsorption of toluene on UiO-66 (Zr) in detail. This work provided new viewpoint to understand the role of concomitant heat contributed to the adsorption and degradation of toluene during photocatalysis.

Strategies to improve adsorption and photocatalytic performance of metal-organic frameworks (MOFs) for perfluoroalkyl and polyfluoroalkyl substances (PFASs) removal from water: A review

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) represent a category of persistent and hazardous organic pollutants extensively prevalent across aquatic environments. The combination of adsorption and photocatalytic degradation has been identified as an effective approach for removing trace amounts of PFASs from water. Among the various materials explored for this purpose, metal-organic frameworks (MOFs) have structural solid tunability, and suitable modification methods could endow them with rich adsorption capabilities and excellent photocatalytic performance, which has potential for applications involving the treatment of trace, multi-chain-length PFASs in water. The research within this realm is currently in its nascent phase, and a holistic knowledge of modification methods can provide a comprehensive framework for future studies. Therefore, this review intends to (1) summarize the mechanism underlying the adsorption and photocatalytic removal of PFASs by MOFs; (2) present various modification methods aimed at enhancing the adsorption and photocatalytic performance of MOFs in alignment with the goal mentioned above; (3) provide an outlook on the prospects of utilizing MOFs for PFASs removal based on current trends and data. Ultimately, the findings from these studies will contribute to advancing knowledge in this area and facilitate the development of effective strategies for addressing PFASs contamination in water systems.

Regulating the Active Sites of Cs2 AgBiCl6 by Doping for Efficient Coupling of Photocatalytic CO2 Reduction and Benzyl Alcohol Oxidation

Halide perovskites exhibit outstanding optoelectronic properties, which make them an ideal choice for photocatalytic CO2 reduction and benzyl alcohol (BA) oxidation. Nevertheless, the simultaneous realization of the above redox coupling reactions on halide perovskites remains a great challenge, as it requires distinct catalytic sites for different target reactions. Herein, the catalytic sites of Cs2 AgBiCl6 (CABC) are regulated by doping Fe for efficient coupling of photocatalytic CO2 reduction and BA oxidation. The Fe-doped CABC (Fe: CABC) exhibits an enhanced visible-light response and effective charge separation. Experimental results and theoretical calculations reveal a synergistic interplay between Bi and Fe sites, where the Bi and Fe sites have lower activation energies toward CO2 reduction and BA oxidation. Further investigations demonstrate that electrons and holes prefer to accumulate at the Bi site and Fe site under light irradiation, respectively, which creates favorable conditions for facilitating CO2 reduction and BA oxidation. The resultant Fe: CABC achieves a high photocatalytic performance toward CO (18.5 µmol g-1  h-1 ) and BD (1.1 mmol g-1  h-1 ) generation, which surpasses most of the state-of-the-art halide photocatalysts. This work demonstrates a facile strategy for regulating the catalytic site for redox coupling reactions, which will pave a new way for designing halide perovskites for photocatalysis.

Simultaneous Detection and Decontamination of Dichromate Ions: The Fluorescence Response and Photocatalysis of Thiadiazole-Modified Zr-Metal-Organic Frameworks

The simultaneous analysis and removal of highly toxic hexavalent chromium (Cr (VI)) in contaminated water via an easy method remain a serious task. Based on the guidance of bibliometric analysis, a thiadiazole ligand-modified zirconium metal-organic framework (Zr-MOF) heralds a new and simple approach to Cr (VI) treatment. The concentration can be determined by fluorescence quenching with a low detection limit of 1.4 μM and a high quenching constant of 6.88 × 103 M-1. For the sensing mechanism, the fluorescence intensity of the Zr-MOF decreased rapidly due to the competition of Cr (VI) with the Zr-MOF for absorption excitation energy and the induction of Zr-MOF aggregation. The analysis system also displayed satisfactory stability and applicability. Apart from sensing application, Zr-MOF can convert Cr (VI) to Cr (III), and the reduction rate constant was 0.004 min-1 under irradiation. Therefore, the bifunctional Zr-MOF provided a potential application method for controlling the pollution caused by Cr (VI) in wastewater.

Rational Atom Substitution to Obtain Efficient, Lead-Free Photocatalytic Perovskites Assisted by Machine Learning and DFT Calculations

Inorganic lead-free halide perovskites, devoid of toxic or rare elements, have garnered considerable attention as photocatalysts for pollution control, CO2 reduction and hydrogen production. In the extensive perovskite design space, factors like substitution or doping level profoundly impact their performance. To address this complexity, a synergistic combination of machine learning models and theoretical calculations were used to efficiently screen substitution elements that enhanced the photoactivity of substituted Cs2 AgBiBr6 perovskites. Machine learning models determined the importance of d10 orbitals, highlighting how substituent electron configuration affects electronic structure of Cs2 AgBiBr6 . Conspicuously, d10 -configured Zn2+ boosted the photoactivity of Cs2 AgBiBr6 . Experimental verification validated these model results, revealing a 13-fold increase in photocatalytic toluene conversion compared to the unsubstituted counterpart. This enhancement resulted from the small charge carrier effective mass, as well as the creation of shallow trap states, shifting the conduction band minimum, introducing electron-deficient Br, and altering the distance between the B-site cations d band centre and the halide anions p band centre, a parameter tuneable through d10 configuration substituents. This study exemplifies the application of computational modelling in photocatalyst design and elucidating structure-property relationships. It underscores the potential of synergistic integration of calculations, modelling, and experimental analysis across various applications.