General Immobilization of Ultrafine Alloyed Nanoparticles within Metal-Organic Frameworks with High Loadings for Advanced Synergetic Catalysis

Epitaxial Metal-Organic Framework-Mediated Electron Relay for H2 Detection on Demand

Hydrogen is regarded as one of the most promising clean substitutes for fossil fuels toward a carbon-zero society. However, the safety management of the upcoming hydrogen energy infrastructure has not been fully prepared, in contrast to the well-established natural gas and gasoline systems. On the frontline is the guard post of hydrogen detectors, which need to be deployed on various structural surfaces and environmental conditions. Conventional hydrogen detectors are usually bulky and environmentally sensitive, limiting their flexible and conformal deployment to various locations, such as pipelines and valves. Herein, we demonstrate the successful synthesis of a palladium-modified epitaxial metal-organic framework (MOF) on single-layer graphene to fabricate a heterostructure material (Epi-MOF-Pd). Device based on the heterostructure demonstrates high sensitivity toward low- concentration H2 (155% resistance response to 1% H2 within 12 s, a theoretical detection limit of 3 ppm). The 25 nm epitaxial MOF acquires electrons from the Pd nanoparticles after the trace amount of H2 is chemically adsorbed and further relays the electrons to the highly conductive graphene. The Epi-MOF-Pd is both flexible and enduring, and maintains stable detection over 10 000 bending cycles. Through photolithography, device arrays with a density of 3000 units/cm2 are successfully fabricated. This versatile material provides a prospective avenue for the mass production of high-performance chemical-sensitive electronics, which could significantly improve the hydrogen safety management on demand.

A Multifunctional Co-Based Metal-Organic Framework as a Platform for Proton Conduction and Ni trophenols Reduction

The design and development of proton conduction materials for clean energy-related applications is obviously important and highly desired but challenging. An ultrastable cobalt-based metal-organic framework Co-MOF, formulated as [Co2(btzip)2(μ2-OH2)] (namely, LCUH-103, H2btzip = 4, 6-bis(triazol-1-yl)-isophthalic acid) had been successfully synthesized via the hydrothermal method. LCUH-103 exhibits a three-dimensional framework and a one-dimensional microporous channel structure with scu topology based on the binuclear metallic cluster {Co2}. LCUH-103 indicated excellent chemical and thermal stability; peculiarly, it can retain its entire framework in acid and alkali solutions with different pH values for 24 h. The excellent stability is a prerequisite for studying its proton conductivity, and its proton conductivity σ can reach up to 1.25 × 10-3 S·cm-1 at 80 °C and 100% relative humidity (RH). In order to enhance its proton conductivity, the proton-conducting material Im@LCUH-103 had been prepared by encapsulating imidazole molecules into the channels of LCUH-103. Im@LCUH-103 indicated an excellent proton conductivity of 3.18 × 10-2 S·cm-1 at 80 °C and 100% RH, which is 1 order of magnitude higher than that of original LCUH-103. The proton conduction mechanism was systematically studied by various detection means and theoretical calculations. Meanwhile, LCUH-103 is also an excellent carrier for palladium nanoparticles (Pd NPs) via a wetness impregnation strategy, and the nitrophenols (4/3/2-NP) reduction in aqueous solution by Pd@LCUH-103 indicated an outstanding conversion efficiency, high rate constant (k), and exceptional cycling stability. Specifically, the k value of 4-NP reduction by Pd@LCUH-103 is superior to many other reported catalysts, and its k value is as high as 1.34 min-1 and the cycling stability can reach up to 6 cycles. Notably, its turnover frequency (TOF) value is nearly 196.88 times more than that of Pd/C (wt 5%) in the reaction, indicating its excellent stability and catalytic activity.

Fluorinated Metal-Organic Frameworks with Dual-Functionalized Linkers to Enhance Photocatalytic H2 Evolution and High Water Adsorption

Photocatalytic H2 evolution has recently attracted much attention due to the reduction of nonrenewable energy sources and the increasing demand for renewable sustainable energies. Meanwhile, metal-organic frameworks (MOFs) are emerging potential photocatalysts due to their structural adaptability, porous configuration, several active sites, and a wide range of performance. Nevertheless, there are still limitations in the photocatalytic H2 evolution reaction of MOFs with higher charge recombination rates. Herein, a copper-organic framework with dual-functionalized linkers {[Cu2(L)(H2O)2]·(5DMF)(4H2O)}n (fluorinated MOF(Cu)-NH2; H4L = 3,5-bis(2,4-dicarboxylic acid)-4-(trifluoromethyl)aniline) and with a rare 2-nodal 4,12-connected shp topology has been synthesized by a ligand-functionalization strategy and evaluated for the photocatalytic production of H2 to overcome this issue. According to the photocatalytic H2 evolution results, fluorinated MOF(Cu)-NH2 showed a hydrogen evolution rate of 63.64 mmol·g-1·h-1 exposed to light irradiation, indicating values 12 times that of the pure ligand when cocatalyst Pt and photosensitizer Rhodamine B were present. In addition, this MOF showed a maximum water absorption of 205 cm3·g-1. When dual-functionalized linkers are introduced to the structure of this MOF, its visible-light absorption increases considerably, which can be associated with nearly narrower energy band gaps (2.18 eV). More importantly, this MOF contributes to water absorption and electron collection and transport, acting as a bridge that helps to separate and transfer photogenerated charges while shortening the electron migration path because of the functional group in its configuration. The current paper seeks to shed light on the design of advanced visible-light photocatalysts with no MOF calcination for H2 photocatalytic production.

Nanosized metal-organic frameworks as unique platforms for bioapplications

Metal-organic frameworks (MOFs) are extremely versatile materials, which serve to create platforms with exceptional porosity and specific reactivities. The production of MOFs at the nanoscale (NMOFs) offers the possibility of creating innovative materials for bioapplications as long as they maintain the properties of their larger counterparts. Due to their inherent chemical versatility, synthetic methods to produce them at the nanoscale can be combined with inorganic nanoparticles (NPs) to create nanocomposites (NCs) with one-of-a-kind features. These systems can be remotely controlled and can catalyze abiotic reactions in living cells, which have the potential to stimulate further research on these nanocomposites as tools for advanced therapies.

Modification of bimetal Zn/ Mg MOF with nanoparticles Fe3O4 and Fe3O4@SiO2, investigation of the peroxidase-like activity of these compounds by calorimetry and fluorimetry methods

In this article; the bimetal metal-organic framework Zn/Mg (Zn/Mg MOF) is synthesized. Then Zn/Mg MOF bimetal was combined with Fe₃O₄ and Fe₃O₄@SiO₂, and composites of Fe₃O₄@ SiO₂/MOF/Dextrin, Fe₃O₄@SiO₂/MOF, Fe₃O₄@MOF/Dextrin and Fe₃O₄@MOF made. The peroxidase-like activity of these compounds was investigated and compared by calorimetric Resazurin (Rz) and O-phenylenediamine (OPD); (Rz-H₂O₂, OPD-H₂O₂) and fluorimetric Rz and terephtalic acid (TA); (Rz-H₂O₂, TA-H₂O₂). The Fe₃O₄@ MOF/Dextrin composite has the highest peroxidase-like activity. The effect factors (amount of pH (6), the values of TA (1.37 mM), H₂O₂ (0.025 mM), reaction time (8.15 min), and amount of Composite (116.67 mg)) to increase the catalytic activity of Fe₃O₄@ MOF/Dextrin measured by chemometrics method. The most suitable linear range of the calibration curve by the TA-H₂O₂ -Composite fluorimetric method is 1-600 μg L^-1, and the detection limit is 2.27 μg L^-1. The relative standard deviation (RSD%) for measuring concentration atropine 1 μg L^-1 (n = 6) is 1.18%. Finally, from this system for measuring atropine extracted by the Liquid-liquid extraction (LLE) method in two types of plants, D. Innoxia north and west and D. stramonium north and west of Iran (118.25 μg L^-1, 79.80 μg L^-1) and (18.477 μg L^-1, 9.27 μg L^-1) used, respectively.

Defined metal atom aggregates precisely incorporated into metal-organic frameworks

Nanosized metal aggregates (MAs), including metal nanoparticles (NPs) and nanoclusters (NCs), are often the active species in numerous applications. In order to maintain the active form of MAs in "use", they need to be anchored and stabilised, preventing agglomeration. In this context, metal-organic frameworks (MOFs), which exhibit a unique combination of properties, are of particular interest as a tunable and porous matrix to host MAs. A high degree of control in the synthesis towards atom-efficient and application-oriented MA@MOF composites is required to derive specific structure-property relationships and in turn to enable design of functions on the molecular level. Due to the versatility of MA@MOF (derived) materials, their applications are not limited to the obvious field of catalysis, but increasingly include 'out of the box' applications, for example medical diagnostics and theranostics, as well as specialised (bio-)sensoring techniques. This review focuses on recent advances in the controlled synthesis of MA@MOF materials en route to atom-precise MAs. The main synthetic strategies, namely 'ship-in-bottle', 'bottle-around-ship', and approaches to achieve novel hierarchical MA@MOF structures are highlighted and discussed while identifying their potential as well as their limitations. Hereby, an overview of standard characterisation methods that enable a systematic analysis procedure and state-of-art techniques that localise MA within MOF cavities are provided. While the perspectives of MA@MOF materials in general have been reviewed various times in the recent past, few atom-precise MAs inside MOFs have been reported so far, opening opportunities for future investigation.

Kinetic Acceleration of Lithium Polysulfide Conversion via a Copper-Iridium Alloying Catalytic Strategy in Li-S Batteries

To solve the shuttle effect of soluble lithium polysulfides (LiPSs), a porous N-doped carbon-supported copper-iridium alloy catalyst composite (CuIr/NC) has been synthesized and served as a modified cathode sulfur host for lithium-sulfur batteries (LSBs). The metal-organic framework-derived calcined carbon frameworks build efficient conductive channels for fast ion/electron transport. Furthermore, alloying noble metals Ir with thiophilic metal Cu provides abundant active sites to effectively capture LiPSs and accelerate the catalytic conversion process, originating from modulating the surface electronic structure of the metal Cu by introducing Ir atoms to affect the 3d-orbital distribution. All of the above are strongly supported by a range of characterization studies and density functional theory calculations. Benefiting from the above advantages, the LSBs generally show satisfactory cycling performance. Apart from exhibiting a terrific initial specific capacity of 1288 mA h g^-1 at 0.2 C, they can also keep long-term cycling stability under a high current density up to 5 C together with a slow specific capacity decay ratio (0.033%) per cycle after 1000 cycles. In addition, it is worth mentioning that a high areal capacity (4.7 mA h cm^-2) with a low E/S ratio (6.2 μL mg^-1) could still be accomplished at higher sulfur loading (4.3 mg cm^-2).

Inert metal induces the modulation of unsaturated aldehyde absorption mode for enhanced selective hydrogenation

Selective hydrogenation of α,β-unsaturated aldehydes to obtain a high yield of unsaturated alcohols is important in industrial production. This is still a great challenge because it is thermally more favorable for the hydrogenation of CC than for the CO bond. Various strategies have been developed to optimize the catalysts for improving selectivity but are usually accompanied by the sacrifice of catalytic activity. Herein, we adopt the inert metal inducement strategy to synthesize a series of Ir-M alloy nanoparticle catalysts. The optimal catalyst IrCd₅ exhibits impressive catalytic performance in the selective hydrogenation of cinnamaldehyde, achieving 96.7% conversion with 94.3% selectivity for cinnamal alcohol, which is far superior to that of the Ir counterpart. Furthermore, the H₂ temperature-programmed desorption (H₂-TPD) test, styrene-TPD test, surface valence band test and density functional theory calculations demonstrate that the adsorption mode of cinnamaldehyde shifted from parallel to vertical configurations after introducing an inert metal. Compared to Ir, the weaker adsorption of alkene and stronger adsorption of the substrate for IrCd₅ lead to the prior adsorption and hydrogenation of the CO bond, thus elevating the selectivity of the cinnamal alcohol. This strategy disperses precious metal nanoparticles effectively, maximizes atomic utilization, and improves the selectivity, which provides a new avenue to design bimetal alloy catalysts for the selective hydrogenation of α,β-unsaturated aldehydes.

Series of TM-OFs as a Platform for Efficient Catalysis and Multifunctional Luminescence Sensing

Three novel porous transition-metal-organic frameworks (TM-OFs), formulated as [Co₃(DCPN)₂(μ₂-OH₂)₄(H₂O)₄](DMF)₂ (1), [Cd₃(DCPN)₂(μ₂-OH₂)₄(H₂O)₄](DMF)₂ (2), and [CdK(DCPN)(DMA)] (3), have been successfully prepared via solvothermal conditions based on a 5-(3',6'-dicarboxylic phenyl) nicotinic carboxylic acid (H₃DCPN) ligand. 1 and 2 both have the same porous 3D network structure with the point symbol of {4¹⁰·6¹⁴·8⁴}·{4⁵·6}₂ based on trinuclear ({Co₃} or {Cd₃}) clusters, indicating a one-dimensional porous channel, and possess excellent water and thermal stability; 3 also displays a porous 3D network structure with a 4-connected sra topology based on the heteronuclear metal cluster {CdK}. Complex 1 can be used to load Pd nanoparticles (Pd NPs) via a wetness impregnation strategy to obtain Pd@1. The reduction of nitrophenols (2-NP, 3-NP, 4-NP) by Pd@1 in aqueous solution shows outstanding conversion, excellent rate constants (k), and remarkable cycling stability due to the synergistic effect of complex 1 and Pd NPs. Luminescence sensing tests confirmed that 2 is a reliable multifunctional chemical sensor with high selectivity and sensitivity for low concentrations of Fe³⁺, Cr₂O₇^2-, CPFX, and NFX. Specifically, 2 shows a fluorescence enhancement behavior toward fluoroquinolone antibiotics (CPFX and NFX), which has not been reported previously in the literature. Moreover, the rational mechanism of fluorescence sensing was also systematically investigated by various detection means and theoretical calculations.

Searching for an Optimal Multi-Metallic Alloy Catalyst by Active Learning Combined with Experiments

Searching for an optimal component and composition of multi-metallic alloy catalysts, comprising two or more elements, is one of the key issues in catalysis research. Due to the exhaustive data requirement of conventional machine-learning (ML) models and the high cost of experimental trials, current approaches rely mainly on the combination of density functional theory and ML techniques. In this study, a significant step is taken toward overcoming limitations by the interplay of experiment and active learning to effectively search for an optimal component and composition of multi-metallic alloy catalysts. The active-learning model is iteratively updated using by examining electrocatalytic performance of fabricated solid-solution nanoparticles for the hydrogen evolution reaction (HER). An optimal metal precursor composition of Pt_0.65 Ru_0.30 Ni_0.05 exhibits an HER overpotential of 54.2 mV, which is superior to that of the pure Pt catalyst. This result indicates the successful construction of the model by only utilizing the precursor mixture composition as input data, thereby improving the overpotential by searching for an optimal catalyst. This method appears to be widely applicable since it is able to determine an optimal component and composition of electrocatalyst without obvious restriction to the types of catalysts to which it can be applied.

High-Temperature Synthesis of Carbon-Supported Bimetallic Nanocluster Catalysts by Enlarging the Interparticle Distance

Supported bimetallic nanoparticle catalysts with small size have attracted wide research attention in catalysis but are difficult to synthesize because high-temperature annealing required for alloying inevitably accelerates metal sintering and leads to larger particles. Here, we report a simple and scalable "critical interparticle distance" method for the synthesis of a family of bimetallic nanocluster catalysts with an average particle size of only 1.5 nm by using large-surface-area carbon black supports at high temperatures, which consist of 12 diverse combinations of 3 noble metals (Pt, Ru, and Rh) and 4 other metals (Cr, Fe, Zr, and Sn). In this strategy, high-temperature treatments ensure the formation of alloyed bimetallic nanoparticles and enlargement of the interparticle distance on high-surface-area supports significantly suppresses metal sintering. The prepared ultrafine Pt₂Sn and RuSn nanocluster catalysts exhibited enhanced performance in catalyzing the synthesis of aromatic secondary amines and the selective hydrogenation of furfural, respectively.

Hierarchical Co@C-N synthesized by the confined pyrolysis of ionic liquid@metal–organic frameworks for the aerobic oxidation of alcohols

Co@C-N with hierarchical pores and highly active sites is synthesized by the pyrolysis of an ionic liquid@metal–organic framework.

Light-Assisted CO2 Hydrogenation over Pd3Cu@UiO-66 Promoted by Active Sites in Close Proximity

CO 2 hydrogenation to methanol has attracted great interest while suffering from low conversion and high energy input. Herein, tiny Pd 3 Cu nanoparticles are confined into a metal-organic framework (MOF), UiO-66, to afford Pd 3 Cu@UiO-66 for CO 2 hydrogenation. Remarkably, it achieves a methanol production rate of 340 µmol g -1 h -1 at 200 °C and 1.25 MPa under light irradiation, far surpassing that in the dark. The photo-generated electron transfer from the MOF to antibonding orbitals of CO 2 * promotes CO 2 activation and HCOO* formation. In addition, the Pd 3 Cu microenvironment plays a critical role in CO 2 hydrogenation. In contrast to the MOF-supported Pd 3 Cu (Pd 3 Cu/UiO-66), the Pd 3 Cu@UiO-66 exhibits a much higher methanol production rate due to the close proximity between CO 2 and H 2 activation sites, which greatly facilitates their interaction and conversion. This work provides a new avenue to the integration of solar and thermal energy for efficient CO 2 hydrogenation under moderate conditions.

Confinement of Ultrasmall Bimetallic Nanoparticles in Conductive Metal-Organic Frameworks via Site-Specific Nucleation

Conductive metal-organic frameworks (cMOFs) are emerging materials for various applications due to their high surface area, high porosity, and electrical conductivity. However, it is still challenging to develop cMOFs having high surface reactivity and durability. Here, highly active and stable cMOF are presented via the confinement of bimetallic nanoparticles (BNPs) in the pores of a 2D cMOF, where the confinement is guided by dipolar-interaction-induced site-specific nucleation. Heterogeneous metal precursors are bound to the pores of 2D cMOFs by dipolar interactions, and the subsequent reduction produces ultrasmall (≈1.54 nm) and well-dispersed PtRu NPs confined in the pores of the cMOF. PtRu-NP-decorated cMOFs exhibit significantly enhanced chemiresistive NO₂ sensing performances, owing to the bimetallic synergies of PtRu NPs and the high surface area and porosity of cMOF. The approach paves the way for the synthesis of highly active and conductive porous materials via bimetallic and/or multimetallic NP loading.

Incorporation of Active Metal Species in Crystalline Porous Materials for Highly Efficient Synergetic Catalysis

The design and development of efficient catalytic materials with synergistic catalytic sites always has long been known to be a thrilling and very dynamic research field. Crystalline porous materials (CPMs) mainly including metal-organic frameworks and zeolites with high scientific and industrial impact have recently been the subject of extensive research due to their essential role in modern chemical industrial processes. The rational incorporation of guest species in CPMs can synergize the respective strengths of these components and allow them to collaborate with each other for synergistic catalysis, leading to enhanced catalytic activity, selectivity, and stability in a broad range of catalytic processes. In this review, the recent advances in the development of CPMs-confined active metal species, including metal nanoparticles, metal/metal oxides heteroparticles, metal oxide, subnanometric metal clusters, and polyoxometalates, for heterogeneous catalysis, with a particular focus on synergistic effects between active components that result in an enhanced performance are highlighted. Insights into catalysts design strategies, host-guest interactions, and structure-property relationships have been illustrated in detail. Finally, the existing challenges and possible development directions in CPMs-based encapsulation-structured synergistic catalysts are discussed.

Metal Sub-nanoclusters Confined within Hierarchical Porous Carbons with High Oxidation Activity

Metal sub-nanoclusters (SNCs) have shown great promise for a variety of catalytic reactions. However, the fabrication of stable metal SNCs simultaneously with high dispersion and high metal contents remains a challenge. Herein, we report a novel and versatile strategy for the synthesis of various bimetal SNCs stabilized within hierarchical porous carbons (HPC). This facile synthesis only involves the self-assembly of a metal-organic framework (MOF) as the precursor, a molten salt assisted pyrolysis process and the final metal replacement. The metal SNCs (mostly less than 0.8 nm) derived from the metal nodes of the MOF are exclusively confined and homogeneously dispersed throughout the organic ligands derived HPC at high loadings (up to 11.2 wt %). The obtained Cu-Pd@HPC composite exhibits superior catalytic activity and recycling durability in the selective transformation of furfural to maleic acid, achieving 97.8 % yield of maleic acid with a TOF value as high as 20.1 h^-1 under mild conditions. DFT calculations reveal that the introduction of Pd shifts the partial density of states of Cu toward the Fermi level, leading to stronger chemisorption of furfural to enhance the catalytic activity.

Controlled growth of ultrafine metal nanoparticles mediated by solid supports

As a unique class of nanomaterials with a high surface-area-to-volume ratio and narrow size distribution, ultrafine metal nanoparticles (UMNPs) have shown exciting properties in many applications, particularly in the field of catalysis. Growing UMNPs in situ on solid supports enables precise control of the UMNP size, and the supports can effectively prevent the aggregation of UMNPs and maintain their high catalytic activity. In this review, we summarize the recent research progress in controlled growth of UMNPs using various solid supports and their applications in catalysis.

Encapsulation of Ultrafine Metal-Organic Framework Nanoparticles within Multichamber Carbon Spheres by a Two-Step Double-Solvent Strategy for High-Performance Catalysts

Carbon-encapsulated metal-organic framework (MOF) composite is one kind of emerging new catalyst with high efficiency and has gained much attention. However, for this kind of composite catalyst, the key to improving its catalytic activity and durability is to realize the effective dispersion of MOF nanoparticles (NPs) and enhance the interaction between MOF NPs and the carbon matrix, which remain a significant challenge. Herein, ultrafine MOF NPs within multichamber carbon spheres (MOF@MCCS), for the first time, have been rationally synthesized by a two-step double-solvent strategy for high-performance catalysts. The precise loading of guest MOFs can be achieved by adjusting the multichamber structure and calcination extent of the multichamber polymer (MCP), and the particle size of MOFs can be as low as 13.2 nm. Due to the formation of abundant carbon defects in the pyrolysis process of MCPs, the special structure and synergistic effect make the material exhibit higher catalytic activity and durability. More importantly, this method is universal and can be extended to different MOF systems. The two-step double-solvent strategy not only prepares a unique structure of MOF@MCCS-type host-guest-encapsulated catalysts but also provides a new idea for the design of high-efficiency catalysts with better performance and higher durability.

Multienzyme-Mimic Ultrafine Alloyed Nanoparticles in Metal Organic Frameworks for Enhanced Chemodynamic Therapy

Nanozyme-based chemodynamic therapy (CDT) has emerged as an effective cancer treatment because of its low side effects and without the requirement of exogenous energy. The therapeutic effect of CDT highlights the pivotal importance of active sites, H₂ O₂ supplement and the glutathione (GSH) depletion of a nanozyme. The construction of a single kind of catalyst with multiple functions for the enhanced CDT is still a big challenge. In this work, seven types of bimetallic nanoparticles are synthesized using a metal-organic framework (MOF) as a stable host instead of a Fenton or Fenton-like ions supplier. Among them, Cu-Pd@MIL-101 with an alloy loading of 9.5 wt% modified by PEG (9.5% CPMP) is found to exhibit the highest peroxidase (POD) like activity combined with a superoxide dismutase (SOD) mimic activity and the function of GSH depletion. The in vivo results suggest that the stable and ultrafine nanoparticles possess favorable CDT effect for tumor and good biosafety as well as biocompatibility. This work has provided a credible strategy to construct nanozymes with an excellent activity and may pave a new way for the design of enhanced tumor CDT treatment.

The robust peroxidase mimics within metal–organic frameworks for the sensitivity detection of H2O2 and glucose in serum

Ultrafine and uniform CuPd alloy nanoparticles encapsuled in MOF to detect H2O2 and glucose with a low detection limit.

Multiple catalytic sites in MOF-based hybrid catalysts for organic reactions

Hybrid catalysis provides an effective pathway to improve the catalytic efficiency and simplify the synthesis operation, but multiple catalytic sites are required. Catalysts with multiple functions based on/derived from metal-organic frameworks (MOFs) have received growing attention in organic synthesis due to their wide variety and outstanding designability. This review provides an overview of significant advances in the field of organic reactions by MOF-based hybrid catalysts with emphasis on multiple catalytic sites and their synergies, including inherent sites on host frameworks, sites of MOF composites and metal sites in/on MOF-derived hybrid catalysts.

MOF-Assisted Synthesis of Highly Mesoporous Cr2O3/SiO2 Nanohybrids for Efficient Lewis-Acid-Catalyzed Reactions

The facile fabrication of porous solid acids is highly desired for replacing hazardous liquid acids for many acid-catalyzed reactions in the industry. Herein, we present a bottom-up strategy to construct ultrastable mesoporous Cr₂O₃/SiO₂ nanohybrids (denoted as Meso-Cr-Si-O) with highly dispersed Lewis acid sites by pyrolysis of a SiO₂@MIL-101 precursor prepared via nanocasting by a reverse double-solvent approach, which can guarantee the efficient encapsulation of SiO₂ nanoparticles (NPs) inside the MIL-101 pores. The pore environment of Meso-Cr-Si-O can be well tuned by simply controlling the amount of silica within the MIL-101 pores and the pyrolysis temperature. Pyridine adsorption experiments demonstrate that the density of Lewis acidic sites in the obtained Meso-Cr-Si-O is much higher than that of MIL-101-derived Cr₂O₃ NPs. Benefitting from its highly mesoporous nanostructure with abundant acid sites, the optimal Meso-Cr-Si-O exhibits a significantly improved catalytic activity for the Lewis-acid-catalyzed Meerwein-Ponndorf-Verley reduction of cyclohexanone with 4.5 times higher yield of cyclohexanol than that of the MIL-101-derived Cr₂O₃ NPs, representing the first efficient Cr₂O₃-based catalytic system for this reaction.

Ultrathin Ni-MOF Nanobelts-Derived Composite for High Sensitive Detection of Nitrite

In this paper, the Ni/NiO ultrathin nanobelts were successively synthesized by a facile in suit conversion process using pre-synthesized Ni-based metal-organic frameworks (MOFs) nanobelts as parent materials to detect the nitrite (NaNO2). The synthesized Ni/NiO composites have the advantages in structure, as follows: (I) Interleaved 3D reticulated structure has strong mechanical stability; (II) Ultrathin nanobelt structures allow more active sites to be exposed and make the transfer of charge faster; (III) A large number of ultrafine Ni nanoparticles decorate the building blocks of the NiO nanobelt and enhance the electrical conductivity. Ni/NiO/GCE has an obvious oxidation peak at 0.78 V, when the concentration is between 0.5 and 1000 μM, the oxidation peak current of NaNO2 is linearly related to the concentration, and the sensitivity is 1.5319 μA mM-1 cm-2 (S/N = 3). Moreover, the experimental results also concluded that the Ni/NiO ultrathin nanobelts not only indicated wonderful reproducibility in the determination of NaNO2 in the pickled pork samples, but also could be well-recovered and keep stable for a long time.

Encapsulation of metal oxide nanoparticles inside metal-organic frameworks via surfactant-assisted nanoconfined space

Encapsulation of metal oxide nanoparticles (MO NPs) inside metal-organic frameworks (MOFs) has been realized successfully via surfactant-assisted nano-confined space strategy, which is a universal method for various MO NPs@MOFs. The size of MO NPs was limited by the confined nano-space and could be adjusted to a certain extent. The synthesis mechanism of MO NPs@MOFs was revealed via detailed structural characterizations and a series of control experiments. Surfactants introduced during MOFs (CuBDC, BDC = 1,4-benzenedicarboxylic acid) formation process plays a very important role in producing uniform voids of nano-confined space. Cu ions in MOF frameworks were directly used as precursors to fabricate CuO NPs in these confined void spaces. The synthesized CuO@CuBDC composites showed excellent catalytic activity in C-S cross-coupling reactions and dye pollutant photo-degradation reactions.

Metal organic frameworks for biomass conversion

This review narrates the recent developments on the catalytic applications of pristine metal–organic frameworks (MOFs), functionalized MOFs, guests embedded over MOFs and MOFs derived carbon composites for biomass conversion into platform chemicals.

Synergistic Effect over Sub-nm Pt Nanocluster@MOFs Significantly Boosts Photo-oxidation of N-alkyl(iso)quinolinium Salts

Quinolones and isoquinolones are of interest to pharmaceutical industry owing to their potent biological activities. Herein, we first encapsulated sub-nm Pt nanoclusters into Zr-porphyrin frameworks to afford an efficient photocatalyst Pt_0.9@PCN-221. This catalyst can dramatically promote electron-hole separation and ¹O₂ generation to achieve synergistic effect first in the metal-organic framework (MOF) system, leading to the highest activity in photosynthesis of (iso)quinolones in >90.0% yields without any electronic sacrificial agents. Impressively, Pt_0.9@PCN-221 was reused 10 times without loss of activity and can catalyze gram-scale synthesis of 1-methyl-5-nitroisoquinolinone at an activity of 175.8 g·g_cat⁻¹, 22 times higher than that of PCN-221. Systematic investigations reveal the contribution of synergistic effect of photogenerated electron, photogenerated hole, and ¹O₂ generation for efficient photo-oxidation, thus highlighting a new strategy to integrate multiple functional components into MOFs to synergistically catalyze complex photoreactions for exploring biologically active heterocyclic molecules.

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A state-of-the-art photocatalyst for preparation of bioactive (iso)quinolones

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Synergistic catalysis of photogenerated e⁻/h⁺ and ¹O₂

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Sub-nm Pt_0.9@PCN-221 with a high efficiency of e⁻-h⁺ separation and ¹O₂ generation

Multishell Hollow Metal/Nitrogen/Carbon Dodecahedrons with Precisely Controlled Architectures and Synergistically Enhanced Catalytic Properties

Multishell hollow nanoarchitectures are one of the most important branches in the nanomaterial field due to their enormous potential in many fields, but synthesizing them in a well-controlled manner remains challenging. Herein, we present a general strategy for the construction of multishell hollow metal/nitrogen/carbon dodecahedrons (metal@NC) with well-defined and precisely controlled architectures. This strategy is based on the pyrolysis of multilayer solid ZIFs prepared by a step-by-step crystal growth approach, which enables precise control over the shell number and composition of the resultant hollow metal@NC. Impressively, our strategy can be further extended to the synthesis of yolk@multishell hollow structures or multishell hollow structures that are assembled by carbon nanotubes. The multishell hollow structures can efficiently facilitate the mass diffusion, which together with the high dispersity and increased surface area are responsible for their significantly enhanced catalytic performances for the selective hydrogenation of biomass-derived furfural to cyclopentanol when compared with their solid and single-shell counterparts. We anticipate that our general strategy would shed light on the rational design and accurate construction of other complex multishell hollow materials for various important yet challenging applications.

Synthesis of Co0.5 Mn0.1 Ni0.4 C2 O4 ⋅n H2 O Micropolyhedrons: Multimetal Synergy for High-Performance Glucose Oxidation Catalysis

Owing to the synergy between metals, trimetal oxalate micropolyhedrons have been synthesized by means of a room-temperature coprecipitation strategy. The effect of their nanoscale size on their electrochemical performance toward glucose oxidation was investigated. In particular, the Co_0.5 Mn_0.1 Ni_0.4 C₂ O₄ ⋅n H₂ O micropolyhedrons illustrated prominent electrocatalytic activity for the glucose oxidation reaction. Additionally, the Co_0.5 Mn_0.1 Ni_0.4 C₂ O₄ ⋅n H₂ O micropolyhedrons, when used as an electrode material, illustrated an excellent lower limit of detection (1.5 μm), a wide detection concentration range (0.5-5065.5 μm), and a high sensitivity (493.5 μA mm^-1  cm^-2 ). Further analysis indicated that the effectively improved conductivity may have been due to the small size of the materials, and it was easier to form a flat film when Nafion was coated onto the glassy carbon electrode.

Cu/Cu2O Nanoparticles Supported on a Phenol-Pyridyl COF as a Heterogeneous Catalyst for the Synthesis of Unsymmetrical Diynes via Glaser-Hay Coupling

Covalent organic frameworks (COFs) are a new class of porous crystalline polymers with a modular construct that favors functionalization. COF pores can be used to grow nanoparticles (nPs) with dramatic size reduction, stabilize them as dispersions, and provide excellent nP access. Embedding substrate binding sites in COFs can generate host-guest synergy, leading to enhanced catalytic activity. In this report, Cu/Cu₂O nPs (2-3 nm) are grown on a COF, which is built by linking a phenolic trialdehyde and a triamine through Schiff bonds. Their micropores restrict the nP to exceptionally small sizes (∼2-3 nm), and the pore walls decorated with strategically positioned hydrogen-bonding phenolic groups anchor the substrates via hydrogen-bonding, whereas the basic pyridyl sites serve as cationic species to stabilize the [Cu_clusterCl₂]^2- type reactive intermediates. This composite catalyst shows high activity for Glaser-Hay heterocoupling reactions, an essential 1,3-diyne yielding reaction with widespread applicability in organic synthesis and material science. Despite their broad successes in homocoupled products, preparation of unsymmetrical 1,3-diynes is challenging due to poor selectivity. Here, our COF-based Cu catalyst shows elevated selectivity toward heterocoupling product(s) (Cu nP loading 0.0992 mol %; turn over frequency: ∼45-50; turn over number: ∼175-190). The reversible redox activity at the Cu centers has been demonstrated by carrying out X-ray photoelectron spectroscopy on the frozen reactions, whereas the crucial interactions between the substrates and the binding sites in their optimized configurations have been modeled using density functional theory methods. This report emphasizes the utility of COFs in developing a heterogeneous catalyst for a truly challenging organic heterocoupling reaction.