Metal Organic Frameworks as Versatile Hosts of Au Nanoparticles in Heterogeneous Catalysis

Highly Dispersive Gold Nanoclusters Confined within Micropores of Defective UiO-66 for Highly Efficient Aldehyde Oxidation at Mild Conditions

The oxidative esterification of aldehydes under mild conditions remains a significant challenge. This study introduces a unique defective UiO-66 to achieve gold nanoclusters (AuNCs) for efficient aldehyde oxidation under mild conditions. The construction and characterization of these materials are thoroughly investigated by techniques of XRD, SEM and TEM images, FT-IR, Raman, and XPS spectrum, emphasizing the unique microporous in defective UiO-66 are conducive to the fabrication of AuNCs. The catalytic performance of the prepared materials in aldehyde oxidation reactions is systematically evaluated, demonstrating the remarkable efficiency of dispersed Au@UiO-66-25 with high-content (9.09 wt%) Au-loading and ultra-small size (~2.7 nm). Moreover, mechanistic insights into the catalytic process under mild conditions (70 °C for 1 h) are provided, elucidating the determination of defective UiO-66 in the confined fabrication of AuNCs and subsequent furfural adsorption, which underlie the principles governing the observed enhancements. This study establishes the groundwork for the synthesis of highly dispersed and catalytically active metal nanoparticles using defective MOFs as a platform, advancing the catalytic esterification reaction of furfural to the next level.

Building respirable powder architectures: utilizing polysaccharides for precise control of particle morphology for enhanced pulmonary drug delivery

INTRODUCTION

Dry powder inhaler (DPI) formulations are gaining attention as universal formulations with applications in a diverse range of drug formulations. The practical application of DPIs to pulmonary drugs requires enhancing their delivery efficiency to the target sites for various treatment modalities. Previous reviews have not explored the relation between particle morphology and delivery to different pulmonary regions. This review introduces new approaches to improve targeted DPI delivery using novel particle design such as supraparticles and metal-organic frameworks based on cyclodextrin.

AREAS COVERED

This review focuses on the design of DPI formulations using polysaccharides, promising excipients not yet approved by regulatory agencies. These excipients can be used to design various particle morphologies by controlling their physicochemical properties and manufacturing methods.

EXPERT OPINION

Challenges associated with DPI formulations include poor access to the lungs and low delivery efficiency to target sites in the lung. The restricted applicability of typical excipients contributes to their limited use. However, new formulations based on polysaccharides are expected to establish a technological foundation for the development of DPIs capable of delivering modalities specific to different lung target sites, thereby enhancing drug delivery.

AuNP/MIL-88B-NH2 Nanocomposite for the Valorization of Nitroarene by Green Catalytic Hydrogenation

The efficiency of a catalytic process is assessed based on conversion, yield, and time effectiveness. However, these parameters are insufficient for evaluating environmentally sustainable research. As the world is urged to shift towards green catalysis, additional factors such as reaction media, raw material availability, sustainability, waste minimization and catalyst biosafety, need to be considered to accurately determine the efficacy and sustainability of the process. By combining the high porosity and versatility of metal organic frameworks (MOFs) and the activity of gold nanoparticles (AuNPs), efficient, cyclable and biosafe composite catalysts can be achieved. Thus, a composite based on AuNPs and the nanometric flexible porous iron(III) aminoterephthalate MIL-88B-NH2 was successfully synthesized and fully characterized. This nanocomposite was tested as catalyst in the reduction of nitroarenes, which were identified as anthropogenic water pollutants, reaching cyclable high conversion rates at short times for different nitroarenes. Both synthesis and catalytic reactions were performed using green conditions, and even further tested in a time-optimizing one-pot synthesis and catalysis experiment. The sustainability and environmental impact of the catalytic conditions were assessed by green metrics. Thus, this study provides an easily implementable synthesis, and efficient catalysis, while minimizing the environmental and health impact of the process.

Advances in the Application of Transition-Metal Composite Nanozymes in the Field of Biomedicine

Due to the limitation that natural peroxidase enzymes can only function in relatively mild environments, nanozymes have expanded the application of enzymology in the biological field by dint of their ability to maintain catalytic oxidative activity in relatively harsh environments. At the same time, the development of new and highly efficient composite nanozymes has been a challenge due to the limitations of monometallic particles in applications and the inherently poor enzyme-mimetic activity of composite nanozymes. The inherent enzyme-mimicking activity is due to Au, Ag, and Pt, along with other transition metals. Moreover, the nanomaterials exhibit excellent enzyme-mimicking activity when composited with other materials. Therefore, this paper focuses on composite nanozymes with simulated peroxidase activity that have been prepared using noble metals such as Au, Ag, and Pt and other transition metal nanoparticles in recent years. Their simulated enzymatic activity is utilized for biomedical applications such as glucose detection, cancer cell detection and tumor treatment, and antibacterial applications.

Constructing FeS and ZnS Heterojunction on N,S-Codoped Carbon as Robust Electrocatalyst toward Oxygen Reduction Reaction

Highly active and cost-efficient electrocatalysts for oxygen reduction reaction (ORR) are significant for developing renewable energy conversion devices. Herein, a nanocomposite Fe/ZnS-SNC electrocatalyst with an FeS and ZnS heterojunction on N,S-codoped carbon has been fabricated via a facile one-step sulfonating of the pre-designed Zn- and Fe-organic frameworks. Benefitting from the electron transfer from FeS to adjacent ZnS at the heterointerfaces, the optimized Fe/ZnS-SNC900 catalyst exhibits excellent ORR performances, featuring the half-wave potentials of 0.94 V and 0.81 V in alkaline and acidic media, respectively, which is competitive with the commercial 20 wt.% Pt/C (0.87 and 0.76 V). The flexible Zn-air battery equipping Fe/ZnS-SNC900 affords a higher open-circuit voltage (1.45 V) and power density of 30.2 mW cm-2. Fuel cells assembled with Fe/ZnS-SNC900 as cathodic catalysts deliver a higher power output of 388.3 and 242.8 mW cm-2 in H2-O2 and -air conditions. This work proposes advanced heterostructured ORR electrocatalysts that effectively promote renewable energy conversions.

Fabrication of Adjustable Au/Carbon Hybrid Nanozymes with Photothermally Enhanced Peroxidase Activity and Ultra-sensitivity for Glutathione Detection

Au nanozymes are extensively researched for their photothermal effect and catalytic performance, but overcoming the inherent defects of poor dispersibility and thermal stability through complementary materials will expand their prospects for biological applications. Herein, several novel CAu nanozymes were fabricated by in situ reduction of chloroauric acid on hollow carbon nanospheres (HCNs). Through regulating the number of reductions, sesame ball-shaped CAu (sCAu) with highly dispersed Au nanoparticles and diversity-shaped CAu (dCAu) were obtained. The number and morphology of loaded Au nanoparticles, absorption spectra, and hydrophilicity of CAu nanozymes were systematically characterized to demonstrate the flexibility of this novel method. The high-efficiency peroxidase-like sCAu0.3 nanozyme with hyperthermia-activated property was then screened for later bio-application. It is worth mentioning that its photothermal-promoted peroxidase-like activity could be achieved under near-infrared laser irradiation. Moreover, sCAu0.3 could specifically achieve glutathione detection in human blood samples. This method will provide a protocol for the regulation of CAu nanozymes to adapt to bio-detection applications.

Synthesis and characterization of PCN-222 metal organic framework and its application for removing perfluorooctane sulfonate from water

Poly- and perfluoro alkyl substances (PFAS) are a group of man-made, notoriously persistent, and highly toxic contaminants in the environment reported worldwide. Many adsorbents including granular activated carbon, graphene, biochar, zeolites, and clay minerals have been tested for PFAS removal from water, but most of these materials suffer from high cost and/or poor removal performance. Here, we synthesized, characterized, and examined the efficiency of PCN-222(Fe), a new porous metal organic framework (MOF) with high water stability, for adsorptive removal of a frequently occurring PFAS, perfluorooctane sulfonate (PFOS), from water. The adsorption isotherm and kinetic studies revealed high PFOS adsorption capacity of PCN-222 (2257 mg/g), with rapid PFOS removal rate (within 30 min). The structure of PCN-222 was unaffected in water in the pH range of 2-10 but disintegrated and lost its PFOS removal ability at pH > 10. The PFOS adsorption on PCN-222 was an endothermic reaction. Electrostatic attraction was a dominant mechanism for PFOS adsorption at < 1694 mg/g PFOS concentration, while hydrophobic interaction accompanied with hydrogen-bonding was responsible at ≥ 1694 mg/g PFOS concentration. The interlayer morphology of PCN-222 did not change due to increasing PFOS loading. The findings of this study demonstrated superior features of PCN-222 over other conventional adsorbents for its potential application in removing PFOS from contaminated water to reduce PFOS transfer from water to living organisms.

CuCo Nanoparticle, Pd(II), and l-Proline Trifunctionalized UiO-67 Catalyst for Three-Step Sequential Asymmetric Reactions

Metal-organic frameworks (MOFs) have become a promising support for different active sites to construct multifunctional and heterogeneous catalysts. However, the related investigation mainly focuses on introducing one or two active sites into MOFs and trifunctional catalysts have been very rarely reported. Herein, non-noble CuCo alloy nanoparticles, Pd²⁺, and l-proline, as encapsulated active species, functional organic linkers, and active metal nodes, respectively, were successfully decorated to UiO-67 to construct a chiral trifunctional catalyst by the one-step method, which was further applied to asymmetric three-step sequential oxidation of aromatic alcohols/Suzuki coupling/asymmetric aldol reactions with excellent oxidation and coupling performance (yields up to 95 and 96%, respectively), as well as good enantioselectivities (ee_anti value up to 73%) in asymmetric aldol reactions. The heterogeneous catalyst can be reused at least five times without obvious deactivation due to the strong interaction between the MOFs and the active sites. This work provides an effective strategy to construct multifunctional catalysts via the introduction and combination of three or more of active sites, including encapsulated active species, functional organic linkers, and active metal nodes, into stable MOFs.

Ag Nanoparticle-Modified Polyoxometalate-Based Metal-Organic Framework for Enhanced CO2 Photoreduction

The photoreduction deposition method is employed to fabricate a family of silver nanoparticle (Ag NP)-modified polyoxometalate-based metal-organic framework (NENU-5) photocatalysts, named Ag/NENU-5. The title photocatalysts, Ag/NENU-5, can be used for the photocatalytic reduction of CO₂ and are observed to efficiently reduce CO₂ into CO, in which the highest reduction rate is 22.28 μmol g^-1 h^-1, 3 times greater than that of NENU-5. Photocatalytic reduction performances of CO₂ have been extremely improved after the incorporation of Ag NPs as the cocatalyst. The enhancement of the photocatalytic reduction of CO₂ has been attributed to the synergistic effects of Ag NPs and NENU-5, inhibiting the charge recombination during the photocatalytic process and increasing the reaction active sites. Furthermore, the influence of Ag NPs on the photocatalytic activity has also been investigated. The experimental results clearly reveal that the size of Ag NPs could exert a main effect on the photocatalytic activity, and the reasonable size of Ag NPs is able to enhance the photocatalytic reduction activity toward CO₂ significantly.

Metal-organic frameworks as a good platform for the fabrication of multi-metal nanomaterials: design strategies, electrocatalytic applications and prospective

MOF-derived multi-metal nanomaterials are attracting numerous attentions in widespread applications such as catalysis, sensors, energy storage and conversion, and environmental remediation. Compared to the monometallic counterparts, the presence of foreign metal is expected to bring new physicochemical properties, thus exhibiting synergistic effect for enhanced performance. MOFs have been proved as a good platform for the fabrication of polymetallic nanomaterials with requisite features. Herein, various design strategies related to constructing multi-metallic nanomaterials from MOFs are summarized for the first time, involving metal nodal substitution, seed epitaxial growth, ion-exchange strategy, guest species encapsulation, solution impregnation and combination with extraneous substrate. Afterwards, the recent advances of multi-metallic nanomaterials for electrocatalytic applications, including oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), are systematically discussed. Finally, a personal outlook on the future trends and challenges are also presented with hope to enlighten deeper understanding and new thoughts for the development of multi-metal nanomaterials from MOFs.

Modulating the Chemical Microenvironment of Pt Nanoparticles within Ultrathin Nanosheets of Isoreticular MOFs for Enhanced Catalytic Activity

The catalytic activity of metal nanoparticles (MNPs) embedded in metal-organic frameworks (MOFs) is affected by the electronic interactions between MNPs and MOFs. In this report, we fabricate a series of ultrathin nanosheets of isoreticular MOFs (NMOFs) with different metal nodes as supports and successfully encapsulate Pt NPs within these NMOFs, affording Pt@NMOF-Co, Pt@NMOF-Ni₁Co₁, Pt@NMOF-Ni₃Co₁, and Pt@NMOF-Ni nanocomposites. The microchemical environment on the surface of Pt NPs can be modulated by varying the metal nodes of NMOFs. The catalytic activity of the nanocomposites toward liquid-phase hydrogenation of 1-hexene shows obvious difference, in which Pt@NMOF-Ni possesses the highest activity followed by Pt@NMOF-Ni₃Co₁, Pt@NMOF-Ni₁Co₁, and Pt@NMOF-Co in a decreasing order of activity. Obviously, increasing gradually the amount of Ni²⁺ nodes in the carriers can improve the catalytic activity. The difference of catalytic activity of the nanocomposites might originate from the distinct electron interactions between Pt NPs and NMOFs, as ascertained by X-ray photoelectron spectroscopy spectrum and density functional theory calculations. This work provides a rare example that the catalytic activity of MNPs could be controlled by accurately regulating the microchemical environment using ultrathin NMOFs as supports.

A coordination cage hosting ultrafine and highly catalytically active gold nanoparticles

Ultrafine metal nanoparticles (MNPs) with size <2 nm are of great interest due to their superior catalytic capabilities. Herein, we report the size-controlled synthesis of gold nanoparticles (Au NPs) by using a thiacalixarene-based coordination cage CIAC-108 as a confined host or stabilizer. The Au NPs encapsulated within the cavity of CIAC-108 (Au@CIAC-108) show smaller size (∼1.3 nm) than the ones (∼4.7 nm) anchored on the surface of CIAC-108 (Au/CIAC-108). The cage-embedded Au NPs can be used as a homogeneous catalyst in a mixture of methanol and dichloromethane while as a heterogeneous catalyst in methanol. The homogeneous catalyst Au@CIAC-108-homo exhibits significantly enhanced catalytic activities toward nitroarene reduction and organic dye decomposition, as compared with its larger counterpart Au/CIAC-108-homo and its heterogeneous counterpart Au@CIAC-108-hetero. More importantly, the as-prepared Au@CIAC-108-homo possesses remarkable stability and durability.

The size-controlled synthesis of Au NPs was achieved by using a coordination cage CIAC-108 as a support. The Au NPs encapsulated within the cavity of CIAC-108 show smaller size (∼1.3 nm) than the ones (∼4.7 nm) anchored on the surface of CIAC-108.

Double-shell microcapsules with spatially arranged Au nanoparticles and single Zn atoms for tandem synthesis of cyclic carbonates

Tandem catalysts with multifunctional sites can achieve high-efficiency catalytic transformations for quickly converting simple raw materials into complex value-added products. The integration of highly active species of metal nanoparticles (NPs) and single-atom catalytic sites (SACs) into one tandem system promises to synthesize an ideal bifunctional catalyst on account of the synergistic effect between NPs and SACs. However, such ideas face some challenges as deactivation or loss of active species, and low efficiency or side reactions caused by the disorder of different active species. Herein, a double-shell microencapsulated nanoreactor was fabricated as a bifunctional catalyst for the one-pot synthesis of cyclic carbonates from olefins. The microcapsules consist of an inner shell of nitrogen-doped porous carbon rich in Zn SACs, an outer shell of mesoporous SiO₂, and Au NPs confined between the outer and inner shells, noted as Zn-N-C/Au@mSiO₂. Particularly, two active species are spatially compartmented within microcapsules. Furthermore, the catalyst was applied in the one-pot synthesis of styrene carbonate from styrene with CO₂ under normal pressure and showed admirable performance. The yield of cyclic carbonate reached 92.9% at 93.2% olefins conversion. Furthermore, the catalyst shows good reusability with little loss of catalytic performance (4.0%) even after using it 15 consecutive times. The unique structure used in this work can rationally integrate diverse catalytic species into one system and offering adequate protection, which provides an effective strategy for the development of multi-site catalysts.

Charge State of Au25(SG)18 Nanoclusters Induced by Interaction with a Metal Organic Framework Support and Its Effect on Catalytic Performance

We investigated the charge transfer between Au₂₅(SG)₁₈ nanoclusters and metal-organic framework (MOF) supports including Mil-101-Cr, Mil-125-Ti, and ZIF-8 by an X-ray photoemission technique and discussed the influence of resulted charge states of supported Au₂₅(SG)₁₈ nanoclusters on the 4-nitrophenol reduction reaction. Charge transfer from Au₂₅(SG)₁₈ to Mil-101-Cr induces positive charge Au^δ+ (0 < δ < 1) while charge transfer from ZIF-8 to Au₂₅(SG)₁₈ generates negative charge Au^δ- due to different metal-support interactions. Au₂₅(SG)₁₈ on Mil-125 shows metallic Au⁰, similar to unsupported Au₂₅(SG)₁₈, due to negligible charge transfer. The resulted charge state of Au^δ- inhibits the formation of adsorbed hydride (H^-) species because of electrostatic repulsion, while Au^δ+ impairs the reductive ability of adsorbed hydride (H^-) species due to strong affinity between them. In comparison, metallic Au⁰ in Au₂₅(SG)₁₈/Mil-125 and unsupported Au₂₅(SG)₁₈ presents the optimum catalytic activity. The current work provides guidelines to design effective metal nanoclusters in heterogeneous catalysis through metal-support interaction exerted by metal-oxo/nitric clusters within MOFs.

Classified Encapsulation of an Organic Dye and Metal-Organic Complex in Different Molecular Compartments for White-Light Emission and Selective Adsorption of C2H2 over CO2

Encapsulating a certain guest molecule in an assigned molecular compartment and then endowing the corresponding potential remains a huge challenge for metal-organic frameworks. To this end, we demonstrate a good example, for the first time, based on an actinide-based MOF. The used MOF (namely, ECUT-300) shows a unique uranyl-TPE anionic skeleton with three distinct cages, viz., mesopore A (2.8 nm), mesopore B (2.0 nm), and micropore C (0.9 nm). Through solid-liquid reaction, a RhB⁺ molecule can be encapsulated into ECUT-300 with the exact location in mesopore B, whereas the encapsulation of a metal-organic cation of [Fe(tpy)₂]³⁺ was observed with the location in micropore C, suggesting unprecedented classified encapsulation. Impressively, the potential of the resulting guest@MOF composites is also highly dependent on the type of encapsulated guest molecules, for example, white-light emission for RhB⁺ and selective adsorption of C₂H₂ over CO₂ for [Fe(tpy)₂]³⁺.

In-situ development of metal organic frameworks assisted ZnMgAl layered triple hydroxide 2D/2D hybrid as an efficient photocatalyst for organic dye degradation

Metal organic framework (MOF) supported layered triple hydroxide (LTH) 2D/2D hybrid material was prepared by a simple hydrothermal method. The photophysical properties of the prepared samples were investigated through a set of analytical methods such as X-ray diffraction, Fourier-transform infrared spectroscopy, field emission scanning electron microscope, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and mapping. The photocatalytic degradation activity of as prepared 2D/2D MOF-5/LTH hybrid sample was investigated against methylene blue (MB) dye under the UV-visible light irradiation. The degradation efficiency of the MOF-5/LTH hybrid sample was twice a time greater than that of pristine MOF-5, particularly degradation efficiency of the MOF-5, LTH and MOF-5/LTH hybrid samples are 43.3, 57.7 and 98.1% respectively. The Pseudo first order rate and the reusing investigation was further used to study the catalytic activity and stability of the as-synthesized 2D/2D photocatalyst. The observed improvement in the photocatalytic activity of the hybrid samples were owed to enhance visible light absorption, efficient separation and transportation of photoinduced electrons and holes.

Confined Generation of Homogeneously Dispersed Au and SnO2 Nanoparticles in Layered Silicate as Synergistic Catalysts

With the aid of the confined conversion of layered silicate RUB-15, homogeneously dispersed Au and SnO₂ nanoparticles (NPs) were generated in the confined layer space of RUB-15. The Au-SnO₂/SiO₂ composite was obtained with the structure that ultrafine Au and SnO₂ NPs were supported on SiO₂ lamellas. Benefited by the Sn(II)-assisted in situ reduction strategy, Au NPs were highly uniformed and evenly distributed in/on the RUB-15. This Au-SnO₂/SiO₂ composite was employed as a catalyst to the reduction of 4-nitrophenol showing excellent catalytic activity. The catalytic rate constant at room temperature was calculated to be 6.64 min^-1, which was dramatically higher than that of Au/SiO₂ composite produced by reduction with hydrazine hydrate on the same support of layered silicate RUB-15. The interaction between Au and SnO₂ NPs increased the electron density around Au NPs, which was demonstrated to be an essential factor to the excellent catalytic activity of the Au-SnO₂/SiO₂ composite. The simple and universal synthesis method afforded precise control over the size/spatial arrangement of Au and SnO₂ NPs on SiO₂ lamellas. The high activity of the Au-SnO₂/SiO₂ composite demonstrated that the strategy used in this study has good potential application prospect. Furthermore, this work provided new perspective on the catalysis mechanism to the metal/semiconductor synergistic catalyst system.

Two-dimensional ultrathin surfactant-encapsulating polyoxometalate assemblies as carriers for monodispersing noble-metal nanoparticles with high catalytic activity and stability

Noble metal nanoparticles (NMNPs) with excellent catalytic activity and stability play an important role in the field of environmental governance. A uniform distribution and a strong binding force with the carriers of the noble metal nanoparticles are important, but avoidance of the use of additional reducing agents is a promising direction of research. Herein, 2D ultrathin surfactant-encapsulating polyoxometalate (SEP) nanosheets constructed by the self-assembly of dodecyldimethylammonium bromide (DODA) and molybdophosphate (H3PMo12O40, PMo12) are designed to be versatile carriers for Ag nanoparticles. Under the synergistic effect of the well-arranged PMo12 units, encapsulating hydrophobic oleic acid (OA) and reductive molybdophosphate under Xe lamp irradiation, the silver oleate (AgOA)-derived Ag nanoparticles (5 ± 2 nm) are monodispersed on the DODA-PMo12 assemblies and form the Agx/DODA-PMo12 composite. The optimized Ag4.89/DODA-PMo12 composite exhibits high catalytic activity and stability in the degradation of 4-nitrophenol (4-NP), which reaches a superior rate constant of 6.49 × 10-3 s-1 and without significant deterioration after three recycles. This technique can be facilely promoted to other noble metal nanoparticles with excellent catalytic activity and stability.

Cobalt-Based Metal Organic Frameworks as Solids Catalysts for Oxidation Reactions

Metal organic frameworks (MOFs) are porous crystalline solids whose frameworks are constituted by metal ions/nodes with rigid organic linkers leading to the formation of materials having high surface area and pore volume. One of the unique features of MOFs is the presence of coordinatively unsaturated metal sites in their crystalline lattice that can act as Lewis acid sites promoting organic transformations, including aerobic oxidation reactions of various substrates such as hydrocarbons, alcohols, and sulfides. This review article summarizes the existing Co-based MOFs for oxidation reactions organized according to the nature of substrates like hydrocarbon, alcohol, olefin, and water. Both aerobic conditions and peroxide oxidants are discussed. Emphasis is placed on comparing the advantages of using MOFs as solid catalysts with respect to homogeneous salts in terms of product selectivity and long-term stability. The final section provides our view on future developments in this field.

Design and application of metal-organic frameworks and derivatives as heterogeneous Fenton-like catalysts for organic wastewater treatment: A review

Advanced oxidation process (AOP), with a high oxidation efficiency, fast reaction speed (relatively no secondary pollution), has become one of the core technologies of industrial wastewater and advanced drinking water treatment. Heterogeneous Fenton-like oxidation process (HFOP) is a kind of AOP, which developed rapidly in recent years in such a way to overcome the disadvantages of traditional Fenton reaction. Metal-organic frameworks (MOFs) and their derivatives become essential heterogeneous catalysts for organics mineralization due to the large specific surface area, abundant active sites, and ease of structural regulation. However, the knowledge gap on the mechanism and the fate of heterogeneous catalyst species during organics degradation activities by MOFs presents considerable impediments, particularly for a wide application and scaling up the process. This work has the potential to provide guidance and ideas for researchers and engineers in the fields of environmental remediation, environmental catalysis and functional materials. This review focuses on clarifying the critical mechanism of •OH production from MOFs and derivatives as well as its action on the organic's degradation process. The recent developments in MOF based HFOP are compared, and more attention is paid for the following aspects in this review: (1) classifies systematically progressive modification methods of MOFs by chemical and physical treatments; (2) analyzes the fate of catalytic species during treating organic wastewater; (3) proposes design ideas and principles for improving the performance of MOFs catalysts; (4) discusses the main factors influencing the catalytic properties and practical application; (5) summarizes the possible research challenges and directions for MOFs and their derivatives as catalysts applied to wastewater treatment in the future.

Fabrication and catalytic performance of a novel tubular PMIA/Ag@RGO nanocomposite nanofiber membrane

A novel tubular PMIA/Ag@RGO composite nanofiber membrane, which could be used in continuous catalysis process was fabricated via a facile and effective method.

Understanding the opportunities of metal–organic frameworks (MOFs) for CO2 capture and gas-phase CO2 conversion processes: a comprehensive overview

The rapid increase in the concentration of atmospheric carbon dioxide is one of the most pressing problems facing our planet.

The role of metal–organic porous frameworks in dual catalysis

Metal–organic frameworks (MOFs) are a valuable group of porous crystalline solids with inorganic and organic parts that can be used in dual catalysis.

Emerging Concepts in Carbon Nitride Organic Photocatalysis

Carbon nitrides encompass a class of transition-metal-free materials possessing numerous advantages such as low cost (few Euros per gram), high chemical stability, broad tunability of redox potentials and optical bandgap, recyclability, and a high absorption coefficient (>10⁵  cm^-1 ), which make them highly attractive for application in photoredox catalysis. In this Review, we classify carbon nitrides based on their unique properties, structure, and redox potentials. We summarize recently emerging concepts in heterogeneous carbon nitride photocatalysis, with an emphasis on the synthesis of organic compounds: 1) Illumination-Driven Electron Accumulation in Semiconductors and Exploitation (IDEASE); 2) singlet-triplet intersystem crossing in carbon nitride excited states and related energy transfer; 3) architectures of flow photoreactors; and 4) dual metal/carbon nitride photocatalysis. The objective of this Review is to provide a detailed overview regarding innovative research in carbon nitride photocatalysis focusing on these topics.

Incorporating Transition-Metal Phosphides Into Metal-Organic Frameworks for Enhanced Photocatalysis

Metal-organic frameworks (MOFs) have been shown to be an excellent platform in photocatalysis. However, to suppress electron-hole recombination, a Pt cocatalyst is usually inevitable, especially in photocatalytic H₂ production, which greatly limits practical application. Herein, for the first time, monodisperse, small-size, and noble-metal-free transitional-metal phosphides (TMPs; for example, Ni₂ P, Ni₁₂ P₅ ), are incorporated into a representative MOF, UiO-66-NH₂ , for photocatalytic H₂ production. Compared with the parent MOF and their physical mixture, both TMPs@MOF composites display significantly improved H₂ production rates. Thermodynamic and kinetic studies reveal that TMPs, behaving similar ability to Pt, greatly accelerate the linker-to-cluster charge transfer, promote charge separation, and reduce the activation energy of H₂ production. Significantly, the results indicate that Pt is thermodynamically favorable, yet Ni₂ P is kinetically preferred for H₂ production, accounting for the higher activity of Ni₂ P@UiO-66-NH₂ than Pt@UiO-66-NH₂ .

Metal Halide Perovskite Nanocrystals in Metal-Organic Framework Host: Not Merely Enhanced Stability

As an emerging optical material, perovskite nanocrystals (NCs) exhibit excellent optoelectronic properties and show great potential for various optoelectronic applications. However, the inherent inferior stability against moisture, oxygen, light and heat limit their practical application. As well, the exploration and development of perovskite NCs with novel properties and functions are new challenges. To achieve these goals, the integration and encapsulation of perovskite NCs with multifunctional metal-organic frameworks (MOFs) to form perovskite NC@MOF composites, is a promising strategy for enhancing the stability and broadening the application scope. In this minireview, we summarize and discuss the synthesis strategies and functional mechanisms of perovskite NC@MOF composites, along with applications of light emitting diodes (LED), information security, photocatalysis, sensing, and detection. We further briefly point out the current challenges as well as the future opportunities for the emerged composite materials.

Hot Electrons, Hot Holes, or Both? Tandem Synthesis of Imines Driven by the Plasmonic Excitation in Au/CeO2 Nanorods

Solar-to-chemical conversion via photocatalysis is of paramount importance for a sustainable future. Thus, investigating the synergistic effects promoted by light in photocatalytic reactions is crucial. The tandem oxidative coupling of alcohols and amines is an attractive route to synthesize imines. Here, we unravel the performance and underlying reaction pathway in the visible-light-driven tandem oxidative coupling of benzyl alcohol and aniline employing Au/CeO₂ nanorods as catalysts. We propose an alternative reaction pathway for this transformation that leads to improved efficiencies relative to individual CeO₂ nanorods, in which the localized surface plasmon resonance (LSPR) excitation in Au nanoparticles (NPs) plays an important role. Our data suggests a synergism between the hot electrons and holes generated from the LSPR excitation in Au NPs. While the oxygen vacancies in CeO₂ nanorods trap the hot electrons and facilitate their transfer to adsorbed O₂ at surface vacancy sites, the hot holes in the Au NPs facilitate the α-H abstraction from the adsorbed benzyl alcohol, evolving into benzaldehyde, which then couples with aniline in the next step to yield the corresponding imine. Finally, cerium-coordinated superoxide species abstract hydrogen from the Au surface, regenerating the catalyst surface.

In Situ One-Step Synthesis of Platinum Nanoparticles Supported on Metal-Organic Frameworks as an Effective and Stable Catalyst for Selective Hydrogenation of 5-Hydroxymethylfurfural

A facile in situ one-step route for the preparation of platinum nanoparticles supported on metal-organic frameworks (MOFs) without adding stabilizing agents was developed. The obtained 10% Pt@MOF-T3 material possessed a large surface area and high crystallinity. Meanwhile, uniform and well-dispersed platinum nanoparticles were formed inside the cavities of MOFs, which could be attributed to the efficient complexation and stabilization effect derived from the dipyridyl groups. The as-synthesized 10% Pt@MOF-T3 sample showed high activity and selectivity in the hydrogenation of 5-hydroxymethylfurfural (HMF). This excellent catalytic performance could be attributed to the synergistic effects of well-dispersed platinum nanoparticles and electron donation offered by MOFs. Meanwhile, the presence of bipyridine ligands in the MOF framework avoided the irreversible adsorption of the hydrocarbon compounds, leading to the enhanced catalytic efficiency. Besides, it was easily recycled and reused at least five times, showing good recyclability.

Plasmon-Induced Water Splitting-through Flexible Hybrid 2D Architecture up to Hydrogen from Seawater under NIR Light

The efficient utilization of solar energy is the actual task of the present and near future. Thus, the preparation of appropriate materials that are able to harvest and utilize the broad wavelength range of solar light (especially commonly ignored near-infrared light region-NIR) is the high-priority challenging mission. Our study provides a rationally designed two-dimensional (2D) flexible heterostructures with photocatalytic activity for the production of "clean" hydrogen under NIR illumination, with the hydrogen production rate exceeding most 2D materials and the ability to use the seawater as a starting material. The proposed design utilizes the hybrid bimetallic (Au/Pt) periodic structure, which is further covalently grafted with a metal-organic framework MIL-101(Cr). The periodic gold structure is able to efficiently support the plasmon-polariton wave and to excite the hot electrons, which is further injected in the Pt and MIL-101(Cr) layers. The Pt and MIL-101(Cr) structures provide catalytic sites, which are saturated with hot electrons and efficiently initiate water splitting and hydrogen production. The MIL-101(Cr) layer also serves for repelling generated hydrogen bubbles. The mechanistic studies reveal the catalytic role of every element of the 2D flexible heterostructures. The maximum hydrogen output was achieved under plasmon resonance excitation in the NIR range, and it could be actively controlled by the applied LED wavelength.