Interfacial Microenvironment Modulation Boosting Electron Transfer between Metal Nanoparticles and MOFs for Enhanced Photocatalysis

Icosahedron kernel defect in Pt1Ag x series of bimetallic nanoclusters enhances photocatalytic hydrogen evolution

Developing high-efficiency photocatalysts for photocatalytic hydrogen production and understanding the structure-property relationships is much desired. In this study, a family of Pt1Ag x (x = 9, 11, 13 and 14) nanoclusters (NCs), including a new Pt1Ag11(SR)5(P(Ph-OMe)3)7 NC, were designed and synthesized via ligand engineering (SR = 2,3,5,6-tetrafluorothiophenol, P(Ph-OMe)3 = tris(4-methylphenyl)phosphine). The positive effect of the kernel structural defect on photocatalytic activity was investigated using the photocatalytic water-splitting reaction as a model, and the mechanistic relationship between the defect structure and catalytic activity was clarified. In this series of Pt1Ag x bimetallic NCs, the Pt1Ag11 NC, which exhibits a distinctive defect-containing icosahedral kernel structure, displayed excellent catalytic performance for photocatalytic hydrogen evolution, with the hydrogen production rate reaching 1780 μmol g-1 h-1. The experimental results revealed that the superior catalytic activity of Pt1Ag11/g-C3N4 may originate from the formation of Z-scheme heterojunction between Pt1Ag11 and the g-C3N4, facilitating efficient electron-hole separation and charge transfer. Furthermore, density-functional theory (DFT) calculations reveal the critical role of the defect-containing icosahedron-kernel on photocatalytic activity, which is favourable for the formation of the most stable nanocomposites and the easy absorption of H* intermediates on the Ag sites in Pt1Ag11/g-C3N4. This paper provides insights into the effect that the defects have on the mechanism of the photocatalytic hydrogen evolution reaction at the atomic level and promotes the rational design of high-efficiency photocatalysts.

Ionic-Fence Effect in Au Nanoparticle-Loaded UiO-66 Metal-Organic Frameworks for Highly Chemoselective Hydrogenation

The chemoselective reaction are vital for fine chemicals, which requires economical and environmentally friendly catalysts. In order to improve the selectivity of multi-reaction competition, herein, we propose a novel ionic-fence strategy to synthesize heterogeneous catalyst for efficient hydrogenation. Practically, UIO-66 metal-organic frameworks (MOF) modified with pyridinium-linker has been constructed through post-synthetic chains with paired anion via quaternization and ion exchange to form ionic-fence MOF (IFMOF-Cl), which can manage the adsorption mode of nitro substrate, further confine the formation of metal nanoparticles with high dispersity. The optimal Au@IFMOF-Cl catalyst demonstrates satisfactory selectivity for hydrogenation of nitro group compared to acetylene group in 4-nitrophenylacetylene. Specifically, it owns a high yield of 4-aminophenylacetylene (~97 %) with ultra-high catalytic efficiency (3880 h-1 TOF) and long stability, far superior to other catalysts without ionic fence effect. Adsorption experiments and density functional theory studies reveal that the incorporation of ionic fence could modulate the adsorption energy of nitro group, which is responsible for the high selectivity enhancement. Notably, this ionic-fence strategy exhibits comprehensive universality towards a wide range of substrates (23 kinds in total), providing a promising avenue for precisely engineering the internal microenvironments of catalysts to achieve highly selective synthesis of fine chemicals.

Harmonizing proton sponge and proton reservoir in conjugated microporous polymers for enhanced photocatalytic hydrogen peroxide production

Photocatalytic technology is highly sought-after for H2O2 production; however, the low selectivity between the oxygen reduction reaction (ORR) and water oxidation reaction (WOR) pathways is the primary factor limiting photocatalytic performance. Herein, a strategy that simulates a proton sponge by integrating aliphatic tertiary amines into conjugated microporous polymers (CMPs) to synthesize PPDI-N is reported. This method uses a carboxylic acid contaminant (2,4-dichlorophenoxyacetic acid, 2,4-D) as the proton reservoir to synergistically expedite the photosynthesis of H2O2 via a selective one-step 2e- ORR. Importantly, with the aid of 2,4-D (acting as both a proton supplier and hole scavenger), the H2O2 production rate of PPDI-N is 4.4-fold higher than that in pure water, reaching 8.15 mmol g-1 within 4 h irradiation time, which is 58.2 times greater at the same pH value. By mimicking a photo Fenton-like process with the assistance of Fe2+, PPDI-N exhibits an unprecedented removal efficiency (>99%) for 300 ppm of 2,4-D within 60 min. As revealed by Kelvin probe force microscopy and electric surface potential calculations, an enhanced built-in electric field was established in PPDI-N. This work provides valuable guidance for advancing CMP photocatalysts and establishes an ideal scenario for enabling simultaneous photocatalytic mineralization of organic contaminants and H2O2 production.

Modulating N-Heterocyclic Microenvironment in β-Ketoenamine Covalent Organic Frameworks to Boost Overall Photosynthesis of H2O2

Covalent Organic Frameworks (COFs) have emerged as promising platforms for photocatalytic synthesis of hydrogen peroxide (H2O2) due to their tunable chemical compositions and efficient catalytic functionalities. Inspired by the role of the microenvironment in enzyme catalysis, this study introduces various N-heterocyclic species into β-ketoenamine COFs (Nx-COFs, where Nx represents the number of nitrogen atoms in the N-heterocycle) to regulate the microenvironment around catalytic sites on acceptor-donor-acceptor (A-D-A) COFs foroverall H2O2 photosynthesis in pure water. The Nx-COFs exhibit distinct H2O2 photosynthetic rates following the number of nitrogen atoms sequence of N3-COF > N2-COF > N1-COF > N0-COF, with N3-COF with triazine structure showing the highest H2O2 generation rate (4881 µmol h-1 g-1) and the decent solar-to-chemical conversion (SCC) efficiency (0.413%), surpassing many existing COF-based catalysts. In situ characterization and theoretical calculations support the experimental results, revealing that N-heterocyclic species promote the photosynthesis of H2O2 through both an indirect stepwise single-electron oxygen reduction reaction (1e- ORR) mechanism and a direct two-electron water oxidation (2e- WOR) pathway. This study advances the design paradigm of photocatalysts by modulating the microenvironment within A-D-A COFs, paving the way for the development of more efficient and robust photocatalytic systems for the overall photosynthesis of H2O2.

Develop Complex Photocatalytic System of D-π-A-type Conjugated Porous Polymers and Benzyl Alcohol Mediated Autocatalysis for Practical Artificial Photosynthesis of H2O2

Artificial photosynthesis of H2O2 is conceived to be an ideal approach for replacing the industrial anthraquinone method that suffers from hefty energy penalties and environmental toxicity. However, the low concentration of H2O2 resides as the biggest hurdle for industrial production. Herein, with a focus on fabricating high-performance heterogeneous photocatalysts and establishing a highly efficient complex photocatalytic system, we report the preparation of D-π-A-type conjugated porous polymers containing a photosensitizer and redox-active anthraquinone moiety for endowing highly efficient H2O2 production up to 3.0 mmol g-1 h-1. Further, by exploiting the autocatalytic photooxidation feature of benzyl alcohol, •OOH as the key species contributing to H2O2 formation received a substantial accumulation, which stems from the collaboration of the photocatalytic and autocatalytic cycle. Mechanistically, the hydrogen bonding and π-π stacking between the photocatalyst and benzyl alcohol are formed to lower the free energy of the transition states, thus leading to unprecedentedly high efficiency in the photosynthesis of H2O2 up to 140.4 mmol g-1 h-1, with the concentration of 35.1 mmol L-1 and an apparent quantum yield of 49%. This work provides critical insights in advancing sustainable energy conversion research.

Synergistic Mechanism of Hydroxyl Regulation and a Polyvinylpyrrolidone Surfactant in Enhancing the Catalytic Oxidation Abilities of BiOBr

The rational design of BiOBr photocatalysts with optimized surface properties and enhanced photooxidative capacities is crucial. This study proposes a synergistic strategy combining hydroxyl-rich solvents with polyvinylpyrrolidone (PVP) surfactants to modulate the structural and electronic properties of BiOBr through a solvothermal approach. The resulting self-assembled microspheres demonstrated exceptional efficiency in degrading ciprofloxacin (CIP), methyl orange (MO), and rhodamine B (RhB). Among the synthesized variants, BiOBr-EG-PVP (fabricated with ethylene glycol and PVP) exhibited the highest photocatalytic activity, achieving near-complete removal of 20 mg/L CIP and RhB within 10 min under visible light irradiation, with degradation rates 60.12-101.73 times higher than pristine BiOBr. The structural characterization revealed that ethylene glycol (EG) not only induced the formation of self-assembled microspheres but also introduced abundant surface hydroxyl groups, which simultaneously enhanced the hole-mediated oxidation capabilities. The incorporation of PVP further promoted the development of hierarchical honeycomb-like microspheres and synergistically enhanced both the hydroxyl group density and photooxidative potential through interfacial engineering. Density functional theory (DFT) calculations confirmed that the enhanced photooxidative performance originated from an increased surface oxygen content. This work elucidates the synergistic effects of hydroxyl-rich solvents and surfactant modification in the fabrication of advanced BiOBr-based photocatalysts, providing new insights for high-performance photocatalysis for environmental remediation.

Design and engineering of microenvironments of supported catalysts toward more efficient chemical synthesis

Catalytic species such as molecular catalysts and metal catalysts are commonly attached to varieties of supports to simplify their separation and recovery and accommodate various reaction conditions. The physicochemical microenvironments surrounding catalytic species play an important role in catalytic performance, and the rational design and engineering of microenvironments can achieve more efficient chemical synthesis, leading to greener and more sustainable catalysis. In this review, we highlight recent works addressing the topic of the design and engineering of microenvironments of supported catalysts, including supported molecular catalysts and supported metal catalysts. Six types of materials, including oxide nano/microparticle, mesoporous silica nanoparticle (MSN), polymer nanomaterial, reticular material, zeolite, and carbon-based nanomaterial, are widely used as supports for the immobilization of catalytic species. We summarize and discuss the synthesis and modification of supports and the positive effects of microenvironments on catalytic properties such as metal-support interaction, molecular recognition, pseudo-solvent effect, regulating mass transfer, steric effect, etc. These design principles and engineering strategies allow access to a better understanding of structure-property relationships and advance the development of more efficient catalytic processes.

Enhanced Photocatalytic Efficiency Through Oxygen Vacancy-Driven Molecular Epitaxial Growth of Metal-Organic Frameworks on BiVO4

Efficient charge separation at the semiconductor/cocatalyst interface is crucial for high-performance photoelectrodes, as it directly influences the availability of surface charges for solar water oxidation. However, establishing strong molecular-level connections between these interfaces to achieve superior interfacial quality presents significant challenges. This study introduces an innovative electrochemical etching method that generates a high concentration of oxygen vacancy sites on BiVO4 surfaces (Ov-BiVO4), enabling interactions with the oxygen-rich ligands of MIL-101. This reduces the formation energy and promotes conformal growth on BiVO4. The Ov-BiVO4/MIL-101 composite exhibits an ideal semiconductor/cocatalyst interface, achieving an impressive photocurrent density of 5.91 mA cm-2 at 1.23 VRHE, along with excellent stability. This high-performing photoanode enables an unbiased tandem device with an Ov-BiVO4/MIL-101-Si solar cell system, achieving a solar-to-hydrogen efficiency of 4.33%. The molecular-level integration mitigates surface states and enhances the internal electric field, facilitating the migration of photogenerated holes into the MIL-101 overlayer. This process activates highly efficient Fe catalytic sites, which effectively adsorb water molecules, lowering the energy barrier for water oxidation and improving interfacial kinetics. Further studies confirm the broad applicability of oxygen vacancy-induced molecular epitaxial growth in various MOFs, offering valuable insights into defect engineering for optimizing interfaces and enhancing photocatalytic activity.

In Situ Integration of Metallic Catalytic Sites and Photosensitive Centers within Covalent Organic Frameworks for the Enhanced Photocatalytic Reduction of CO2

Covalent organic frameworks (COFs) are a promising platform for heterogeneous photocatalysis due to their stability and design diversity, but their potential is often restricted by unmanageable targeted excitation and charge transfer. Herein, a bimetallic COF integrating photosensitizers and catalytic sites is designed to facilitate locally ultrafast charge transfer, aiming to improve the photocatalytic reduction of CO2. The strategy uses a "one-pot" method to synthesize the bimetallic COF (termed PBCOFRuRe) through in situ Schiff-base condensation of Pyrene with MBpy (M = Ru, Re) units. In this structure, Ru and Re are anchored within bipyridine as the photosensitive center and catalytic site, respectively. The bimetallic architecture of PBCOFRuRe significantly boosts the photocatalytic efficiency for CO2 reduction, achieving an impressive CO yield of 8306.6 µmol g-1 h-1 with 99.8% selectivity, surpassing most reported COF materials. This improvement is attributed to the localized ultrafast charge transfer (0.23 ps) from Ru to Re, as demonstrated by femtosecond transient absorption spectroscopy (TAS). Further investigations demonstrate its heterogeneous feature, showcasing exceptional long-term stability and recyclability. This study represents a versatile approach for designing bimetallic COFs with ultrafast charge transfer, paving the pathway for advancements in artificial photosynthesis.

Rapid and dual-mode nitrite detection with improved sensitivity by nanointerface-regulated ultrafast Griess assay

BACKGROUND

The rapid and sensitive detection of nitrite is important to human health protection due to its carcinogenic and teratogenic risks with excessive intake. The Griess assay is widely applied for the design of nitrite detection system. However, its relatively slow reaction kinetics and sole colorimetry mode might limit it's the sensitivity and practical application. Therefore, it is highly desirable to explore new detection method with rapid kinetics and multi-mode recognition characters.

RESULTS

We report a rapid and colorimetry and fluorimetry dual-mode sensing of nitrite by using N-(1-naphthalene)-ethylenediamine-derivated carbon dots (NETH-CDs) as the reporters. NETH-CDs show maximum excitation and emission around 359 nm and 431 nm, accompanying with a quantum yield of 27.1 %. The carbonization of NETH not only increases the fluorescence sensing mode, but also promotes the nanointerfacial Griess assay reaction kinetics within 1 min. High selectivity of dual-mode sensing is exhibited due to the specific reaction. The linear ranges in colorimetry and fluorimetry modes are 0.2-100 μM, and the corresponding limit of detection values are determined to be 0.10 and 0.08 μM, respectively. In addition, the accurate nitrite analysis in urine and serum samples with NETH-CDs nanoprobes. Moreover, the visual nitrite detection is achieved based on NETH-CD-loaded test strips.

SIGNIFICANCE

This work reports a new dual mode nitrite detection method for the first time by NETH-CDs supported ultrafast interfacial Griess assay, it not only explores sensitive nitrite detection probe, but also provides deep understanding of the relationship between chemical reaction kinetics and interfacial interaction on nanosurface. We believe our findings would benefit the exploration of rapid and sensitive detection systems toward various targets by regulating interfacial chemistry.

Metal-organic frameworks (MOFs) of an MIL-101-supported iridium(III) complex as efficient photocatalysts in the three-component alkoxycyanomethylation of alkenes

Metal-organic frameworks (MOFs) exhibit intriguing physicochemical properties due to their manageable structure, abundant porosity, and uniform pore size, which provide ideal environments for photocatalysts to achieve highly efficient photocatalysis. In this work, fac-Ir(ppy)3 is directly anchored to MOFs of MIL-101 with different morphologies via Friedel-Crafts alkylation, affording various MIL-101-supported fac-Ir(ppy)3 without the molecular modification of fac-Ir(ppy)3. The as-fabricated photocatalysts possess high specific surface areas (785-962 m2 g-1), pore volumes (0.42-0.47 cc g-1) and uniform pore sizes (∼1.9 nm). The luminescence properties of anchored fac-Ir(ppy)3 including emission lifetime, band gap energy and quantum yield are enhanced by fabricating a hollow interior and double shell in the frameworks of MIL-101 through etching with acetic acid. In the visible light-induced three-component alkoxycyanomethylation of styrenes with bromoacetonitriles and methanol, comparable catalytic activities (66-90%) to homogeneous fac-Ir(ppy)3 (69-90%) are achieved at room temperature. Furthermore, owing to the good chemical and mechanical stability of the catalyst, no significant decrease in yield (<2%) is observed over ten catalytic cycles. Overall, this study provides a mass/charge transfer-enhanced platform for supported photocatalysts to achieve highly efficient synthesis of fine chemicals in the field of heterogeneous photocatalysis.

Flexible Scaffold Modulation of Spatial Structure and Function of Hierarchically Porous Nanoparticle@ZIF-8 Composites to Enhance Field Deployable Disease Diagnostics

Catalytic nanoparticle@metal-organic framework (MOF) composites have attracted significant interest in point-of-care testing (POCT) owing to their prominent catalytic activity. However, the trade-off between high loading efficiency and high catalytic activity remains challenging because high concentrations of nanoparticles tend to cause the misjoining and collapse of the MOFs. Herein, a facile strategy is reported to encapsulate high concentrations of platinum (Pt) nanoparticles into zeolitic imidazolate framework-8 (ZIF-8) using polydopamine (PDA) as a support for Pt@ZIF-8 and as a flexible scaffold for further immobilization of Pt nanoparticles. The resulting composite (Pt@ZIF-8@PDA@Pt) exhibits ultrahigh Pt nanoparticle loading efficiency, exceptional catalytic activity, stability, and a bright colorimetric signal. Following integration with lateral flow immunoassay (LFIA), the detection limits for pre- and post-catalysis detection of B-type natriuretic peptide (NT-proBNP) are 0.18 and 0.015 ng mL-1, respectively, representing a 6-fold and 70-fold improvement compared to gold nanoparticle-based LFIA. Moreover, Pt@ZIF-8@PDA@Pt-based LFIA achieves 100% diagnostic sensitivity for NT-proBNP in a cohort of 184 clinical samples.

Tailoring the d-Band Center of WS2 by Metal and Nonmetal Dual-Doping for Enhanced Electrocatalytic Nitrogen Reduction

Tuning the adsorption energy of nitrogen intermediates and lowering the reaction energy barrier is essential to accelerate the kinetics of nitrogen reduction reaction (NRR), yet remains a great challenge. Herein, the electronic structure of WS2 is tailored based on a metal and nonmetal dual-doping strategy (denoted Fe, F-WS2) to lower the d-band center of W in order to optimize the adsorption of nitrogen intermediates. The obtained Fe, F-WS2 nanosheet catalyst presents a high Faradic efficiency (FE) of 22.42% with a NH3 yield rate of 91.46 µg h-1 mgcat. -1. The in situ characterizations and DFT simulations consistently show the enhanced activity is attributed to the downshift of the d-band center, which contributes to the rate-determining step of the second protonation to form N2H2 * key intermediates, thereby boosting the overall nitrogen electrocatalysis reaction kinetics. This work opens a new avenue to enhanced electrocatalysis by modulating the electronic structure and surrounding microenvironment of the catalytic metal centers.

Construction of COF/COF Organic S-Scheme Heterostructure for Enhanced Overall Water Splitting

Covalent organic frameworks (COFs) as a new type of photocatalysts have shown unique advantages in visible-light-driven hydrogen evolution, while the reported overall water-splitting systems are still very rare among various COF-based photocatalysts. Herein, two COFs are integrated to construct a type of organic S-scheme heterojunction for improved overall water splitting. In this system, TpBpy-COF and COF-316 serve as H2- and O2-evolving components, respectively, which are combined through π-π interaction between conjugated aromatic rings. By introducing ultra-small Pt nanoparticles (NPs) into the pores of the TpBpy-COF nanosheets (NS), the resultant COF-316/Pt@TpBpy-COF NS heterostructure achieves extremely high H2 and O2 evolution rates of 220.4 and 110.2 µmol g-1 h-1, respectively, under visible light irradiation (λ ≥ 420 nm). The results of transient absorption spectra (TAS) and photoelectronic measurements indicate that the organic heterojunction interface notably facilitates the separation and transfer of photogenerated electron-hole pairs. Further, theoretical calculations and in situ experiments confirm the spontaneous formation of the COF/COF heterojunction interface and the active sites for overall water splitting.

Enhanced peroxidase-like activity based on electron transfer between platinum nanoparticles and Ti3C2TX MXene nanoribbons coupled smartphone-assisted hydrogel platform for detecting mercury ions

BACKGROUND

Heavy metal pollution poses a serious threat to the ecological environment. Mercury ion (Hg2+) is a class of highly toxic heavy metal ions, which is bioaccumulative, difficult to breakdown, and has a significant affinity with sulfur and thiol-containing proteins, which seriously affects environmental safety and human health. Nanozyme-based sensing methods are expected to be used to detect toxic heavy metal ions. However, the application of precious metal nanozymes to develop portable sensors with simplicity, high stability, and high sensitivity has not been explored to a large extent.

RESULTS

In this paper, based on MXene's unique adsorption capacity for certain precious metal ions, PtNPs/Ti3C2TXNR composites were successfully prepared by in-situ growth of Pt nanoparticles (PtNPs) on the surface of Ti3C2TX MXene nanoribbons (Ti3C2TXNR) using the hydrothermal technique. Experimental data revealed PtNPs/Ti3C2TXNR exhibited superior peroxidase-like activity, attributed to the synergistic effect of well-dispersed ultrasmall PtNPs and electron transfer effect. Hg2+ can significantly inhibit enzyme-like activity of PtNPs/Ti3C2TXNR due to specific capture and partial in-situ reduction of PtNPs, so a colorimetric sensor was constructed for ultra-trace detection of Hg2+ with a linear range of 0.2 nM and 400 nM. Furthermore, using the portable detecting capabilities of smartphones and hydrogel, a smartphone-assisted hydrogel sensing platform of Hg2+ was constructed. Notably, the two-mode sensing platforms exhibited outstanding detection performance with LOD values as low as 15 pM (colorimetric) and 26 pM (hydrogel), respectively, superior to recently reported nanozyme-based Hg2+ sensors.

SIGNIFICANCE

Compared with other methods, the PtNPs/Ti3C2TXNR-based dual-mode sensor designed in this paper has superior sensitivity, high selectivity, simple operation and portability. In particular, the dual-output sensing strategy enables self-confirmation of detection results, greatly improving the reliability of the sensor, and is expected to be used for the on-site determination of trace mercury ions.

Microenvironment Engineering of Heterogeneous Catalysts for Liquid-Phase Environmental Catalysis

Environmental catalysis has emerged as a scientific frontier in mitigating water pollution and advancing circular chemistry and reaction microenvironment significantly influences the catalytic performance and efficiency. This review delves into microenvironment engineering within liquid-phase environmental catalysis, categorizing microenvironments into four scales: atom/molecule-level modulation, nano/microscale-confined structures, interface and surface regulation, and external field effects. Each category is analyzed for its unique characteristics and merits, emphasizing its potential to significantly enhance catalytic efficiency and selectivity. Following this overview, we introduced recent advancements in advanced material and system design to promote liquid-phase environmental catalysis (e.g., water purification, transformation to value-added products, and green synthesis), leveraging state-of-the-art microenvironment engineering technologies. These discussions showcase microenvironment engineering was applied in different reactions to fine-tune catalytic regimes and improve the efficiency from both thermodynamics and kinetics perspectives. Lastly, we discussed the challenges and future directions in microenvironment engineering. This review underscores the potential of microenvironment engineering in intelligent materials and system design to drive the development of more effective and sustainable catalytic solutions to environmental decontamination.

Pt-N catalytic centres concisely enhance interfacial charge transfer in amines functionalized Pt@MOFs for selective conversion of CO2 to CH4

Improving ligand-to-active metal charge transfer (LAMCT) by finely tuning the organic ligand is a decisive strategy to enhance charge transfer in metal organic frameworks (MOFs)-based catalysts. However, in most MOFs loaded with active metal catalysts, electron transmission encounters massive obstacle at the interface between the two constituents owing to poor LAMCT. Herein, amines (-NH2) functionalized MOFs (NH2-MIL-101(Cr)) encapsulated active metal Pt nanoclusters (NCs) catalysts are synthesized by the polyol reduction method and utilized for the photoreduction of CO2. Surprisingly, the introduction of -NH2 (electron donating) groups within the matrix of MIL-101(Cr) improved the electron migration through the LAMCT process, fostering a synergistic interaction with Pt. The combined experimental analysis exposed the high number of metallic Pt (Pt0) in Pt@NH2-MIL-101(Cr) catalyst through seamless electron shuttling from N of -NH2 group to excited Pt generating versatile hybrid Pt-N catalytic centres. Consequently, these versatile hybrid catalytic centres act as electro-nucleophilic centres, which enable the efficient and selective conversion of CO bond in CO2 to harvest CH4 (131.0 µmol.g-1) and maintain excellent stability and selectivity for consecutive five rounds, superior to Pt@MIL-101(Cr) and most reported catalysts. Our study verified that the precise tuning of organic ligands in MOFs immensely improves the surface-active centres, electron migration, and catalytic selectivity of the excited Pt NCs catalysts encaged inside MOFs through an improved LAMCT pathway.

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.

Hydrophobic Microenvironment Modulation of Ru Nanoparticles in Metal-Organic Frameworks for Enhanced Electrocatalytic N2 Reduction

The modulation of the chemical microenvironment surrounding metal nanoparticles (NPs) is an effective means to enhance the selectivity and activity of catalytic reactions. Herein, a post-synthetic modification strategy is developed to modulate the hydrophobic microenvironment of Ru nanoparticles encapsulated in a metal-organic framework (MOF), MIP-206, namely Ru@MIP-Fx (where x represents perfluoroalkyl chain lengths of 3, 5, 7, 11, and 15), in order to systematically explore the effect of the hydrophobic microenvironment on the electrocatalytic activity. The increase of perfluoroalkyl chain length can gradually enhance the hydrophobicity of the catalyst, which effectively suppresses the competitive hydrogen evolution reaction (HER). Moreover, the electrocatalytic production rate of ammonia and the corresponding Faraday efficiency display a volcano-like pattern with increasing hydrophobicity, with Ru@MIP-F7 showing the highest activity. Theoretical calculations and experiments jointly show that modification of perfluoroalkyl chains of different lengths on MIP-206 modulates the electronic state of Ru nanoparticles and reduces the rate-determining step for the formation of the key intermediate of N2H2 *, leading to superior electrocatalytic performance.

Photocatalytic Hydrosilylation over Pt@UiO-66-NH2: Enhanced Activity and Polymerization Kinetics

Metal-organic frameworks (MOFs) have shown great research and application value in various types of hydrosilylation reactions. However, studies on photocatalysis-induced hydrosilylation using MOFs are extremely rare. Metal nanoparticles (MNPs)@MOFs are extensively studied for their excellent structural tunability and photocatalytic activity, but there are few reports on their application in photocatalytic hydrosilylation. Here, a novel photocatalyst consisting of platinum (Pt) nanoparticles immobilized in a MOF framework is synthesized and used for photocatalytic hydrosilylation. The effects of various factors on hydrosilylation conversion are investigated, including catalyst concentration, substrate ratio, and irradiation intensity. Furthermore, the photoreactivity of the synthesized Pt catalyst is evaluated in the presence of different concentrations of 2-chlorothixanthone as a photosensitizer. It is noteworthy that the conversion of the reaction increases with increasing catalyst concentration or photosensitizer concentration, whereas increasing the polymethylhydrosiloxane content does not lead to a significant increase in conversion. This study demonstrates the potential of MNPs@MOFs as efficient photocatalysts for photoinduced hydrosilylation reactions and paves the way for future applications in this area.

Cyano-deficient g-C3N4 for round-the-clock photocatalytic degradation of tetracycline: Mechanism and application prospect evaluation

Without light at night, the system for photocatalytic degradation of refractory organic pollutants in aquatic environments based on free radicals will fall into a dormant state. Hence, a round-the-clock photocatalyst (CCN@SMSED) was prepared by in situ growth of cyanide-deficient g-C3N4 on the surface of Sr2MgSi2O7:Eu2+,Dy3+ through a simple calcination method. The CCN@SMSED exhibits an outstanding oxidative degradation ability for refractory tetracycline (TC) in water under both light and dark conditions, which is attributed to the synergistic effect of free radical (•O2- and •OH) and non-radical (h+ and 1O2). Electrochemical analyses further indicate that direct electron transfer (DET) is also one of the reasons for the efficient degradation of TC. Remarkably, the continuous working time of the round-the-clock photocatalyst in a dark environment was estimated for the first time (about 2.5 h in this system). The degradation pathways of TC mainly include demethylation, ring opening, deamination and dehydration, and the growth of Staphylococcus aureus shows that the process is biosafe. More importantly, CCN@SMSED holds significant promise for practical application due to its low energy consumption and suitability for removing TC from a variety of complex water bodies. This work provides an energy consumption reference for the practical application of round-the-clock photocatalytic degradation of organic pollutants.

Introducing Hydrogen-Bonding Microenvironment in Close Proximity to Single-Atom Sites for Boosting Photocatalytic Hydrogen Production

Inspired by enzymatic catalysis, it is crucial to construct hydrogen-bonding-rich microenvironment around catalytic sites; unfortunately, its precise construction and understanding how the distance between such microenvironment and catalytic sites affects the catalysis remain significantly challenging. In this work, a series of metal-organic framework (MOF)-based single-atom Ru1 catalysts, namely, Ru1/UiO-67-X (X = -H, -m-(NH2)2, -o-(NH2)2), have been synthesized, where the distance between the hydrogen-bonding microenvironment and Ru1 sites is modulated by altering the location of amino groups. The -NH2 group can form hydrogen bonds with H2O, constituting a unique microenvironment that causes an increased water concentration around the Ru1 sites. Remarkably, Ru1/UiO-67-o-(NH2)2 displays a superior photocatalytic hydrogen production rate, ∼4.6 and ∼146.6 times of Ru1/UiO-67-m-(NH2)2 and Ru1/UiO-67, respectively. Both experimental and computational results suggest that the close proximity of amino groups to the Ru1 sites in Ru1/UiO-67-o-(NH2)2 improves charge transfer and H2O dissociation, accounting for the promoted photocatalytic hydrogen production.

Synergistic Construction of Sub-Nanometer Channel Membranes through MOF-Polymer Composites: Strategies and Nanofiltration Applications

The selective separation of small molecules at the sub-nanometer scale has broad application prospects in the field, such as energy, catalysis, and separation. Conventional polymeric membrane materials (e.g., nanofiltration membranes) for sub-nanometer scale separations face challenges, such as inhomogeneous channel sizes and unstable pore structures. Combining polymers with metal-organic frameworks (MOFs), which possess uniform and intrinsic pore structures, may overcome this limitation. This combination has resulted in three distinct types of membranes: MOF polycrystalline membranes, mixed-matrix membranes (MMMs), and thin-film nanocomposite (TFN) membranes. However, their effectiveness is hindered by the limited regulation of the surface properties and growth of MOFs and their poor interfacial compatibility. The main issues in preparing MOF polycrystalline membranes are the uncontrollable growth of MOFs and the poor adhesion between MOFs and the substrate. Here, polymers could serve as a simple and precise tool for regulating the growth and surface functionalities of MOFs while enhancing their adhesion to the substrate. For MOF mixed-matrix membranes, the primary challenge is the poor interfacial compatibility between polymers and MOFs. Strategies for the mutual modification of MOFs and polymers to enhance their interfacial compatibility are introduced. For TFN membranes, the challenges include the difficulty in controlling the growth of the polymer selective layer and the performance limitations caused by the "trade-off" effect. MOFs can modulate the formation process of the polymer selective layer and establish transport channels within the polymer matrix to overcome the "trade-off" effect limitations. This review focuses on the mechanisms of synergistic construction of polymer-MOF membranes and their structure-nanofiltration performance relationships, which have not been sufficiently addressed in the past.

Superhydrophobic MOF/polymer composite with hierarchical porosity for boosting catalytic performance in an humid environment

The poor hydrostability of most reported metal-organic frameworks (MOFs) has become a daunting challenge in their practical applications. Recently, MOFs combined with multifunctional polymers can act as a functional platform and exhibit unique catalytic performance; they can not only inherit the outstanding properties of the two components but also offer unique synergistic effects. Herein, an original porous polymer-confined strategy has been developed to prepare a superhydrophobic MOF composite to significantly enhance its moisture or water resistance. The selective nucleation and growth of MOF nanocrystals confined in the pore of PDVB-vim are closely related to the structure-directing and coordination-modulating properties of PDVB-vim. The resultant MOF/PDVB-vim composite not only produces superior superhydrophobicity without significantly disturbing the original features but also exhibits a novel catalytic activity in the Friedel-Crafts alkylation reaction of indoles with trans-β-nitrostyrene because of the accessible sites and synergistic effects.

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.

Ferrocene-functionalized zirconium-oxo clusters for achieving high-performance thermocatalytic redox reactions

The Zr(IV) ions are easily hydrolyzed to form oxides, which severely limits the discovery of new structures and applications of Zr-based compounds. In this work, three ferrocene (Fc)-functionalized Zr-oxo clusters (ZrOCs), Zr9Fc6, Zr10Fc6 and Zr12Fc8 were synthesized through inhibiting the hydrolysis of Zr(IV) ions, which show increased nuclearity and regular structural variation. More importantly, these Fc-functionalized ZrOCs were used as heterogeneous catalysts for the transfer hydrogenation of levulinic acid (LA) and phenol oxidation reactions for the first time, and displayed outstanding catalytic activity. In particular, Zr12Fc8 with the largest number of Zr active sites and Fc groups can achieve > 95% yield for LA-to-γ-valerolactone within 4 h (130 °C) and > 98% yield for 2,3,6-trimethylphenol-to-2,3,5-trimethyl-p-benzoquinone within 30 min (80 °C), showing the best catalytic performance. Catalytic characterization combined with theory calculations reveal that in the Fc-functionalized ZrOCs, the Zr active sites could serve as substrate adsorption sites, while the Fc groups could act as hydrogen transfer reagent or Fenton reagent, and thus achieve effectively intramolecular metal-ligand synergistic catalysis. This work develops functionalized ZrOCs as catalysts for thermal-triggered redox reactions.

Dual interfacing with metallic cobalt boosts the electron shuttle of CdS-carbide nanoassemblies

Harnessing accelerated interfacial redox, thus boosting charge separation, is of great importance in photocatalytic solar hydrogen generation. In effect, nanoassembling non-noble metallic phases in CdS-based systems and elucidating their role in photocatalysis hold the key to eventually boosting electron shuttle in the field. Here we combine an efficient in-situ exsoluted metallic Co0 nanoparticles on a carbides matrix (CMG) with CdS (CdS@CoCMG) for photogeneration of hydrogen. The metallic cobalt phase exhibits strong binding at the CdS-carbide dual interfaces, forming the accelerated "electron converter" mechanism validated by charge transfer kinetics and achieving two orders of magnitude faster hydrogen production (44.42 mmol g-1 h-1) relative to CdS (0.43 mmol g-1 h-1). We propose that the unique catalyst configuration enable the directional electron-relay photocatalysis via harnessing interfaces between Co0 phase, carbides, and CdS clusters, which eventually boosts the redox process and charge separation of the integrated system, leading to high H2 production rates in the suspension.

CoP/Co heterojunction on porous g-C3N4 nanosheets as a highly efficient catalyst for hydrogen generation

Designing non-precious catalysts to synergistically achieve a facilitated exposure of abundant active sites is highly desired but remains a significant challenge. Herein, a hetero-structured catalyst CoP-Co supported on porous g-C3N4 nanosheets (CoP-Co/CN-I) was prepared by pyrolysis and P-inducing strategy. The optimal catalyst achieves a turnover frequency (TOF) of 26 min-1 at room temperature and the apparent activation energy (Ea) is 35.5 kJ·mol-1. The catalytic activity is ranked top among the non-precious metal phosphides or the other supports. Meanwhile, the catalytic activity has no significant decrease even after 5 cycles. The CoP/Co interfaces provide richly exposed active sites, optimize hydrogen/water absorption free energy via electronic coupling, and thus improve the catalytic activity. The experimental results reveal that the CoP/Co heterojunction improves the catalytic activity due to the construction of dual-active sites. This research facilitates the innovative construction of non-noble metal catalysts to meet industrial demand for heterogeneous catalysis.

Functionalized Linear Conjugated Polymer/TiO2 Heterojunctions for Significantly Enhancing Photocatalytic H2 Evolution

Conjugated polymers (CPs) have attracted much attention in recent years due to their structural abundance and tunable energy bands. Compared with CP-based materials, the inorganic semiconductor TiO2 has the advantages of low cost, non-toxicity and high photocatalytic hydrogen production (PHP) performance. However, studies on polymeric-inorganic heterojunctions, composed of D-A type CPs and TiO2, for boosting the PHP efficiency are still rare. Herein, an elucidation that the photocatalytic hydrogen evolution activity can actually be improved by forming polymeric-inorganic heterojunctions TFl@TiO2, TS@TiO2 and TSO2@TiO2, facilely synthesized through efficient in situ direct C-H arylation polymerization, is given. The compatible energy levels between virgin TiO2 and polymeric semiconductors enable the resulting functionalized CP@TiO2 heterojunctions to exhibit a considerable photocatalytic hydrogen evolution rate (HER). Especially, the HER of TSO2@TiO2 heterojunction reaches up to 11,220 μmol g-1 h-1, approximately 5.47 and 1260 times higher than that of pristine TSO2 and TiO2 photocatalysts. The intrinsic merits of a donor-acceptor conjugated polymer and the interfacial interaction between CP and TiO2 account for the excellent PHP activity, facilitating the separation of photo-generated excitons. Considering the outstanding PHP behavior, our work discloses that the coupling of inorganic semiconductors and suitable D-A conjugated CPs would play significant roles in the photocatalysis community.

Enhanced Charge Transfer via S-Scheme Heterojunction Interface Engineering of Supramolecular SubPc-Br/UiO-66 Arrays for Efficient Photocatalytic Oxidation

Constructing heterojunction of supramolecular arrays self-assembled on metal-organic frameworks (MOFs) with elaborate charge transfer mechanisms is a promising strategy for the photocatalytic oxidation of organic pollutants. Herein, H12 SubPcB-Br (SubPc-Br) and UiO-66 are used to obtain the step-scheme (S-scheme) heterojunction SubPc-Br/UiO-66 for the first time, which is then applied in the photocatalytic oxidation of minocycline. Atomic-level B-O-Zr charge-transfer channels and van der Waals force connections synergistically accelerated the charge transfer at the interface of the SubPc-Br/UiO-66 heterojunction, while the establishment of the B-O-Zr bonds also led to the directional transfer of charge from SubPc-Br to UiO-66. The synergy is the key to improving the photocatalytic activity and stability of SubPc-Br/UiO-66, which is also verified by various characterization methods and theoretical calculations. The minocycline degradation efficiency of supramolecular SubPc-Br/UiO-66 arrays reach 90.9% within 30 min under visible light irradiation. The molecular dynamics simulations indicate that B-O-Zr bonds and van der Waals force contribute significantly to the stability of the SubPc-Br/UiO-66 heterojunction. This work reveals an approach for the rational design of semiconducting MOF-based heterojunctions with improved properties.

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.

Promoting Photocatalytic Activity of NH2-MIL-125(Ti) for H2 Evolution Reaction through Creation of TiIII- and CoI-Based Proton Reduction Sites

Titanium-based metal-organic framework, NH2-MIL-125(Ti), has been widely investigated for photocatalytic applications but has low activity in the hydrogen evolution reaction (HER). In this work, we show a one-step low-cost postmodification of NH2-MIL-125(Ti) via impregnation of Co(NO3)2. The resulting Co@NH2-MIL-125(Ti) with embedded single-site CoII species, confirmed by XPS and XAS measurements, shows enhanced activity under visible light exposure. The increased H2 production is likely triggered by the presence of active CoI transient sites detected upon collection of pump-flow-probe XANES spectra. Furthermore, both photocatalysts demonstrated a drastic increase in HER performance after consecutive reuse while maintaining their structural integrity and consistent H2 production. Via thorough characterization, we revealed two mechanisms for the formation of highly active proton reduction sites: nondestructive linker elimination resulting in coordinatively unsaturated Ti sites and restructuring of single CoII sites. Overall, this straightforward manner of confinement of CoII cocatalysts within NH2-MIL-125(Ti) offers a highly stable visible-light-responsive photocatalyst.

Selectivity Control in the Direct CO Esterification over Pd@UiO-66: The Pd Location Matters

The selectivity control of Pd nanoparticles (NPs) in the direct CO esterification with methyl nitrite toward dimethyl oxalate (DMO) or dimethyl carbonate (DMC) remains a grand challenge. Herein, Pd NPs are incorporated into isoreticular metal-organic frameworks (MOFs), namely UiO-66-X (X=-H, -NO2 , -NH2 ), affording Pd@UiO-66-X, which unexpectedly exhibit high selectivity (up to 99 %) to DMC and regulated activity in the direct CO esterification. In sharp contrast, the Pd NPs supported on the MOF, yielding Pd/UiO-66, displays high selectivity (89 %) to DMO as always reported with Pd NPs. Both experimental and DFT calculation results prove that the Pd location relative to UiO-66 gives rise to discriminated microenvironment of different amounts of interface between Zr-oxo clusters and Pd NPs in Pd@UiO-66 and Pd/UiO-66, resulting in their distinctly different selectivity. This is an unprecedented finding on the production of DMC by Pd NPs, which was previously achieved by Pd(II) only, in the direct CO esterification.

Anion-induced electronic localization and polarized cobalt clusters for highly efficient water splitting

It is a promising pathway to use anions to regulate electronic structures, reasonably design and construct highly efficient catalysts for water splitting. Herein, a N-regulated Co cluster catalyst confined in carbon nanotubes, N-Co NCNTs, was constructed successfully. Nitrogen anions played a crucial role in optimizing the electronic structures of Co clusters and enhancing localization of electrons, resulting in polarized cobalt clusters. The N-induced electronic localization and the resulting polarized Co clusters are responsible for the improvement of catalytic activity. N-Co NCNTs exhibited ultra-low overpotentials of 178 mV and 92 mV for the OER and HER to achieve 10 mA cm-2 in an alkaline electrolyte, respectively. Its long-term catalytic durability is mainly attributed to the obstacle to the surface oxidation of Co clusters caused by N-regulation. N-Co NCNTs maintained a stable current density for 160 h at 10 mA cm-2. DFT computations confirmed the decisive role played by nitrogen anions in regulating the electronic structure. This work provides a pathway for understanding and designing highly efficient anion-regulated catalysts.

Coherent Sub-Nanometer Interface between Crystalline and Amorphous Materials Boosts Electrochemical Synthesis of Hydrogen Peroxide

There are enormous yet largely underexplored exotic phenomena and properties emerging from interfaces constructed by diverse types of components that may differ in composition, shape, or crystal structure. It remains poorly understood the unique properties a coherent interface between crystalline and amorphous materials may evoke, and there lacks a general strategy to fabricate such interfaces. It is demonstrated that by topotactic partial oxidation heterostructures composed of coherently registered crystalline and amorphous materials can be constructed. As a proof-of-concept study, heterostructures consisting of crystalline P3 N5 and amorphous P3 N5 Ox can be synthesized by creating amorphous P3 N5 Ox from crystalline P3 N5 without interrupting the covalent bonding across the coherent interface. The heterostructure is dictated by nanometer-sized short-range-ordered P3 N5 domains enclosed by amorphous P3 N5 Ox matrix, which entails simultaneously fast charge transfer across the interface and bicomponent synergistic effect in catalysis. Such a P3 N5 /P3 N5 Ox heterostructure attains an optimal adsorption energy for *OOH intermediates and exhibits superior electrocatalytic performance toward H2 O2 production by adopting a selectivity of 96.68% at 0.4 VRHE and a production rate of 321.5 mmol h-1 gcatalyst -1 at -0.3 VRHE . The current study provides new insights into the synthetic strategy, chemical structure, and catalytic property of a sub-nanometer coherent interface formed between crystalline and amorphous materials.

Visible-light-induced photocatalytic CO2 reduction over zirconium metal organic frameworks modified with different functional groups

The reduction of CO₂ into high value-added chemicals and fuels by a photocatalytic technology can relieve energy shortages and the environmental problems caused by greenhouse effects. In the current work, an amino-functionalized zirconium metal organic framework (Zr-MOF) was covalently modified with different functional groups via the condensation of Zr-MOF with 2-pyridinecarboxaldehyde (PA), salicylaldehyde (SA), benzaldehyde (BA), and trifluoroacetic acid (TA), named Zr-MOF-X (X = PA, SA, BA, and TA), respectively, through the post-synthesis modification. Compared with Zr-MOF and Zr-MOF-TA, the introduction of PA, SA, or BA into the framework of Zr-MOF can not only enhance the visible-light harvesting and CO₂ capture, but also accelerate the photogenerated charge separation and transfer, thereby improving the photocatalytic ability of Zr-MOF for CO₂ reduction. These results indicate that the modification of Zr-MOF with electron-donating groups can promote the photocatalytic CO₂ reduction. Therefore, the current work provides an instructive approach to improve the photocatalytic efficiency of CO₂ reduction through the covalent modification of MOFs.

Fast photocatalytic degradation of rhodamine B using indium-porphyrin based cationic MOF under visible light irradiation

A broad light-harvesting range and efficient charge separation are two main ways to enhance the visible photocatalytic performance of semiconductors. Herein, an ionic porphyrin MOF [In(TPyP)]·(NO3) (1) (TPyP = 5,10,15,20-tetrakis(4-pyridyl)-21H,23H-porphyrin) was synthesized via in situ metalation. The orderly arranged porphyrin photosensitizer and the internal electric field between the MOF host and NO3- guests enable effective visible light response and electron-hole separation. Consequently, the as-synthesized MOF shows efficient photocatalytic degradation of rhodamine B (RhB), methyl orange (MO) and methylene blue (MB) organic pollutants. It can degrade 99.07% of RhB within only 20 minutes under visible light irradiation (λ > 420 nm) with a high chemical reaction rate constant of 0.2400 min-1. The photocatalytic activity of the title MOF is more efficient than those of other reported MOFs, COFs and even inorganic semiconductors. The reusability, energy level, band gap, charge distribution and main degradation mechanisms of the photocatalyst were well studied.

Topological Insulator Bi2 Se3 -Assisted Heterostructure for Ultrafast Charging Sodium-Ion Batteries

The development of fast charging materials offers a viable solution for large-scale and sustainable energy storage needs. However, it remains a critical challenge to improve the electrical and ionic conductivity for better performance. Topological insulator (TI), a topological quantum material that has attracted worldwide attention, hosts unusual metallic surface states and consequent high carrier mobility. Nevertheless, its potential in promising high-rate charging capability has not been fully realized and explored. Herein, a novel Bi2 Se3 -ZnSe heterostructure as excellent fast charging material for Na+ storage is reported. Ultrathin Bi2 Se3 nanoplates with rich TI metallic surfaces are introduced as an electronic platform inside the material, which greatly reduces the charge transfer resistance and improves the overall electrical conductivity. Meanwhile, the abundant crystalline interfaces between these two selenides promote Na+ migration and provide additional active sites as well. As expected, the composite delivers the excellent high-rate performance of 360.5 mAh g-1 at 20 A g-1 and maintains its electrochemical stability of 318.4 mAh g-1 after 3000 long cycles, which is the record high for all reported selenide-based anodes. This work is anticipated to provide alternative strategies for further exploration of topological insulators and advanced heterostructures.

Confining charge-transfer complex in a metal-organic framework for photocatalytic CO2 reduction in water

In the quest for renewable fuel production, the selective conversion of CO₂ to CH₄ under visible light in water is a leading-edge challenge considering the involvement of kinetically sluggish multiple elementary steps. Herein, 1-pyrenebutyric acid is post-synthetically grafted in a defect-engineered Zr-based metal organic framework by replacing exchangeable formate. Then, methyl viologen is incorporated in the confined space of post-modified MOF to achieve donor-acceptor complex, which acts as an antenna to harvest visible light, and regulates electron transfer to the catalytic center (Zr-oxo cluster) to enable visible-light-driven CO₂ reduction reaction. The proximal presence of the charge transfer complex enhances charge transfer kinetics as realized from transient absorption spectroscopy, and the facile electron transfer helps to produce CH₄ from CO₂. The reported material produces 7.3 mmol g^-1 of CH₄ under light irradiation in aqueous medium using sacrificial agents. Mechanistic information gleans from electron paramagnetic resonance, in situ diffuse reflectance FT-IR and density functional theory calculation.

Surface ligand-assisted synthesis and biomedical applications of metal-organic framework nanocomposites

Metal-organic framework (MOF) nanocomposites have recently gained intensive attention for biosensing and disease therapy applications owing to their outstanding physiochemical properties. However, the direct growth of MOF nanocomposites is usually hindered by the mismatched lattice in the interface between the MOF and other nanocomponents. Surface ligands, molecules with surfactant-like properties, are demonstrated to exhibit the robust capability to modify the interfacial properties of nanomaterials and can be utilized as a powerful strategy for the synthesis of MOF nanocomposites. Besides this, surface ligands also exhibit significant functions in the morphological control and functionalization of MOF nanocomposites, thus greatly enhancing their performance in biomedical applications. In this review, the surface ligand-assisted synthesis and biomedical applications of MOF nanocomposites are comprehensively reviewed. Firstly, the synthesis of MOF nanocomposites is discussed according to the diverse roles of surface ligands. Then, MOF nanocomposites with different properties are listed with their applications in biosensing and disease therapy. Finally, current challenges and further directions of MOF nanocomposites are presented to motivate the development of MOF nanocomposites with elaborate structures, enriched functions, and excellent application prospects.

Hydrogen-Bond Regulation of the Microenvironment of Ni(II)-Porphyrin Bifunctional Electrocatalysts for Efficient Overall Water Splitting

Accurately regulating the microenvironment around active sites is an important approach for boosting the overall water splitting performance of bifunctional electrocatalysts, which can drive both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in the same electrolyte. Herein, pseudo-pyridine-substituted Ni(II)-porphyrins (o-NiTPyP, m-NiTPyP, and p-NiTPyP) with pseudo-pyridine N-atoms located at the ortho-, meta-, or para-position are prepared and used as model catalysts for alkaline water splitting. Experimental and theoretical results reveal that the pseudo-pyridine N-atom positions can regulate the microenvironment around the active sites and the adsorption free energy of H-donating substances by affecting the H-bonding interaction and the NNiN bond angles of active sites, and thus those pseudo-pyridine-substituted Ni(II)-porphyrins deliver better electrocatalytic activity than the Ni(II)-tetraphenylporphyrin (NiTPP) without pseudo-pyridine N-atoms. Among them, m-NiTPyP on carbon nanotubes delivers the lowest overpotentials of 267 and 138 mV at 10 mA cm^-2 for the OER and HER, respectively. Specifically, m-NiTPyP as bifunctional electrocatalyst in an alkaline electrolyzer requires only 1.62 V to drive efficient overall water splitting at 10 mA cm^-2 while remaining durable. This work proposes a new H-bond-regulating approach of the microenvironment of electrocatalysts for effectively boosting the overall water splitting activity and deeply understanding its related mechanism.

High-Performance Visible-Light Photocatalysts for H2 Production: Rod-Shaped Co3O4/CoO/Co2P Heterojunction Derived from Co-MOF-74

Photocatalyst systems generally consist of catalysts and cocatalysts to realize light capture, charge carrier migration, and surface redox reactions. Developing a single photocatalyst that performs all functions while minimizing efficiency loss is extremely challenging. Herein, rod-shaped photocatalysts Co₃O₄/CoO/Co₂P are designed and prepared using Co-MOF-74 as a template, which displays an outstanding H₂ generation rate of 6.00 mmol·g^-1·h^-1 when exposed to visible light irradiation. It is 12.8 times higher than pure Co₃O₄. Under light excitation, the photoinduced electrons migrate from the catalysts of Co₃O₄ and CoO to the cocatalyst Co₂P. The trapped electrons can subsequently undergo a reduction reaction to produce H₂ on the surface. Density functional theory calculations and spectroscopic measurements reveal that enhanced performance results from the extended lifetime of photogenerated carriers and higher charge transfer efficiency. The ingenious structure and interface design presented in this study may guide the general synthesis of metal oxide/metal phosphide homometallic composites for photocatalysis.

Electronic State and Microenvironment Modulation of Metal Nanoparticles Stabilized by MOFs for Boosting Electrocatalytic Nitrogen Reduction

Modulation of the local electronic structure and microenvironment of catalytic metal sites plays a critical role in electrocatalysis, yet remains a grand challenge. Herein, PdCu nanoparticles with an electron rich state are encapsulated into a sulfonate functionalized metal-organic framework, UiO-66-SO₃ H (simply as UiO-S), and their microenvironment is further modulated by coating a hydrophobic polydimethylsiloxane (PDMS) layer, affording PdCu@UiO-S@PDMS. This resultant catalyst presents high activity toward the electrochemical nitrogen reduction reaction (NRR, Faraday efficiency: 13.16%, yield: 20.24 µg h^-1 mg_cat. ^-1 ), far superior to the corresponding counterparts. Experimental and theoretical results jointly demonstrate that the protonated and hydrophobic microenvironment supplies protons for the NRR yet suppresses the competitive hydrogen evolution reaction reaction, and electron-rich PdCu sites in PdCu@UiO-S@PDMS are favorable to formation of the N₂ H* intermediate and reduce the energy barrier of NRR, thereby accounting for its good performance.

Achieving High-Efficient Photoelectrocatalytic Degradation of 4-Chlorophenol via Functional Reformation of Titanium-Oxo Clusters

Rational design of crystalline catalysts with superior light absorption and charge transfer for efficient photoelectrocatalytic (PEC) reaction coupled with energy recovery remains a great challenge. In this work, we elaborately construct three stable titanium-oxo clusters (TOCs, Ti₁₀Ac₆, Ti₁₀Fc₈, and Ti₁₂Fc₂Ac₄) modified with a monofunctionalized ligand (9-anthracenecarboxylic acid (Ac) or ferrocenecarboxylic acid (Fc)) and bifunctionalized ligands (Ac and Fc). They have tunable light-harvesting and charge transfer capacities and thus can serve as outstanding crystalline catalysts to achieve efficient PEC overall reaction, that is, the integration of anodic organic pollutant 4-chlorophenol (4-CP) degradation and cathodic wastewater-to-H₂ conversion. These TOCs can all exhibit very high PEC activity and degradation efficiency of 4-CP. Especially, Ti₁₂Fc₂Ac₄ decorated with bifunctionalized ligands exhibits better PEC degradation efficiency (over 99%) and H₂ generation than Ti₁₀Ac₆ and Ti₁₀Fc₈ modified with a monofunctionalized ligand. The study of the 4-CP degradation pathway and mechanism revealed that such better PEC performance of Ti₁₂Fc₂Ac₄ is probably due to its stronger interactions with the 4-CP molecule and better ^•OH radical production. This work not only presents the effective combination of organic pollutant degradation and simultaneously H₂ evolution reaction using crystalline coordination clusters as both anodic and cathodic catalyst but also develops a new PEC application for crystalline coordination compounds.

Electron transfer in heterojunction catalysts

Heterojunction catalysis, the cornerstone of the modern chemical industry, shows potential to tackle the growing energy and environmental crises. Electron transfer (ET) is ubiquitous in heterojunction catalysts, and it holds great promise for improving the catalytic efficiency by tuning the electronic structures or building internal electric fields at interfaces. This perspective summarizes the recent progress of catalysis involving ET in heterojunction catalysts and pinpoints its crucial role in catalytic mechanisms. We specifically highlight the occurrence, driving forces, and applications of ET in heterojunction catalysis. For corroborating the ET processes, common techniques with measurement principles are introduced. We end with the limitations of the current study on ET, and envision future challenges in this field.

Active site identification and CO oxidation in UiO-66-XX thin films

Metal-organic frameworks (MOFs) offer an intrinsically porous and chemically tunable platform for gas adsorption, separation, and catalysis. We investigate thin film derivatives of the well-studied Zr-O based MOF powders to understand their adsorption properties and reactivity with their adaption to thin films, involving diverse functionality with the incorporation of different linker groups and the inclusion of embedded metal nanoparticles: UiO-66, UiO-66-NH₂, and Pt@UiO-66-NH₂. Using transflectance IR spectroscopy, we determine the active sites in each film upon consideration of the acid-base properties of the adsorption sites and guest species, and perform metal-based catalysis with CO oxidation of a Pt@UiO-66-NH₂film. Our study shows how surface science characterization techniques can be used to characterize the reactivity and the chemical and electronic structure of MOFs.

Locking Effect in Metal@MOF with Superior Stability for Highly Chemoselective Catalysis

Ultrasmall metal nanoparticles (NPs) show high catalytic activity in heterogeneous catalysis but are prone to reunion and loss during the catalytic process, resulting in low chemoselectivity and poor efficiency. Herein, a locking effect strategy is proposed to synthesize high-loading and ultrafine metal NPs in metal-organic frameworks (MOFs) for efficient chemoselective catalysis with high stability. Briefly, the MOF ZIF-90 with aldehyde groups cooperating with diamine chains via aldimine condensation was interlocked, which was employed to confine in situ formation of Au NPs, denoted as Au@L-ZIF-90. The optimized Au@L_a-ZIF-90 has highly dispersed Au NPs (2.60 ± 0.81 nm) with a loading amount around 22 wt % and shows a great performance toward 3-aminophenylacetylene (3-APA) from the selective hydrogenation of 3-nitrophenylacetylene (3-NPA) with a high yield (99%) and excellent durability (over 20 cycles), far superior to contrast catalysts without chains locking and other reported catalysts. In addition, experimental characterization and systematic density functional theory calculations further demonstrate that the locked MOF modulates the charge of Au nanoparticles, making them highly specific for nitro group hydrogenation to obtain 3-APA with high selectivity (99%). Furthermore, this locking effect strategy is also applicable to other metal nanoparticles confined in a variety of MOFs, and all of these catalysts locked with chains show great selectivity (≥90%) of 3-APA. The proposed strategy in this work provides a novel and universal method for precise control of the inherent activity of accessible metal nanoparticles with a programmable MOF microenvironment toward highly specific catalysis.

Zr- and Ti-based metal-organic frameworks: synthesis, structures and catalytic applications

Recently, Zr- and Ti-based metal-organic frameworks (MOFs) have gathered increasing interest in the field of chemistry and materials science, not only for their ordered porous structure, large surface area, and high thermal and chemical stability, but also for their various potential applications. Particularly, the unique features of Zr- and Ti-based MOFs enable them to be a highly versatile platform for catalysis. Although much effort has been devoted to developing Zr- and Ti-based MOF materials, they still suffer from difficulties in targeted synthesis, especially for Ti-based MOFs. In this Feature Article, we discuss the evolution of Zr- and Ti-based MOFs, giving a brief overview of their synthesis and structures. Furthermore, the catalytic uses of Zr- and Ti-based MOF materials in the previous 3-5 years have been highlighted. Finally, perspectives on the Zr- and Ti-based MOF materials are also proposed. This work provides in-depth insight into the advances in Zr- and Ti-based MOFs and boosts their catalytic applications.

Photo-Induced Switching of CO2 Hydrogenation Pathway towards CH3 OH Production over Pt@UiO-66-NH2 (Co)

It is highly desired to achieve controllable product selectivity in CO₂ hydrogenation. Herein, we report light-induced switching of reaction pathways of CO₂ hydrogenation towards CH₃ OH production over actomically dispersed Co decorated Pt@UiO-66-NH₂ . CO, being the main product in the reverse water gas shift (RWGS) pathway under thermocatalysis condition, is switched to CH₃ OH via the formate pathway with the assistance of light irradiation. Impressively, the space-time yield of CH₃ OH in photo-assisted thermocatalysis (1916.3 μmol g_cat ^-1  h^-1 ) is about 7.8 times higher than that without light at 240 °C and 1.5 MPa. Mechanism investigation indicates that upon light irradiation, excited UiO-66-NH₂ can transfer electrons to Pt nanoparticles and Co sites, which can efficiently catalyze the critical elementary steps (i.e., CO₂ -to-*HCOO conversion), thus suppressing the RWGS pathway to achieve a high CH₃ OH selectivity.