Regioselective Ring-Opening of Terminal Epoxides Catalyzed by a Porous Metal Silicate Material.

Reductive ring-opening of epoxides is a green pathway for synthesizing highly value-added alcohols. In this study, we present a practically applicable approach for the synthesis of anti-Markovnikov-type alcohols with high yields from aliphatic and aromatic epoxides under mild conditions by developing porous metal silicate (PMS) catalysts. A PMS material PMS-20 consists of cobalt and nickel bimetal redox-active sites, exhibiting exceptional catalytic activity and selectivity in the reductive ring-opening of terminal epoxides with >99% yield of primary alcohols. Comparing with the existing methods using noble metals, PMS-20 exhibits broad substrate scope and excellent functional group tolerance by synergistic work between cobalt and nickel species, which is clarified by dual chamber cell system characterization and theoretical calculation results.

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

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

Stabilization of transition metal heterojunctions inside porous materials for high-performance catalysis.

Transition metal-based heterostructural materials are a class of very promising substitutes for noble metal-based catalysts for high-performance catalysis, due to their inherent internal electric field at the interface in the heterojunctions, which could induce electron relocalization and facilitate charge carrier migration between different metal sites at heterostructural boundaries. However, redox-active metal species suffer from reduction, oxidation, migration, aggregation, leaching and poisoning in catalysis, which results in heavy deterioration of the catalytic properties of transition metal-based heterojunctions and frustrates their practical applications. To improve the stability of transition metal-based heterojunctions and sufficiently expose redox-active sites at the heterosurfaces, many kinds of porous materials have been used as porous hosts for the stabilization of non-precious metal heterojunctions. This review article will discuss recently developed strategies for encapsulation and stabilization of transition metal heterojunctions inside porous materials, and highlight their improved stability and catalytic performance through the spatial confinement effect and synergistic interaction between the heterojunctions and the host matrices.

Confining Bimetal Sites in Porous Metal Silicate Materials for Aerobic Oxidation of Phenols under Mild Conditions.

Inspired by the unique catalytic properties of enzymes, numerous biomimetic catalysts have been developed with the intention to realize activation of unreactive reactants under mild conditions; however, the requirement of harsh activation conditions heavily deters their practical applications. We report herein a porous metal silicate (PMS) material PMS-12 that consists of redox-active copper and vanadium metal sites, which exhibits similar catalytic behaviors of enzymes by synergistically activating different reactant molecules and generating local redox potential to facilitate electron and charge transfer, demonstrating the highest catalytic efficiency for aerobic oxidation of phenols to produce highly value-added benzoquinones under mild conditions. Therefore, this work paves a practically applicable strategy for developing high-performance heterogeneous catalysts, which could activate unreactive reactant molecules to produce highly value-added chemicals under mild conditions.

Creation and stabilization of carbon dots in silica-confined compartments with high thermal stability.

Inspired by the formation procedures and high stability of ambers, we report herein a facile approach for the in situ creation and stabilization of carbon dots (CDs) in confined silica compartments by a solvothermal reaction and subsequent thermal treatment, and the endowed CDs exhibit the initial photoluminescence (PL) properties at 400 °C, which could be used to fabricate highly thermal-stable light-emitting diodes (LEDs) that work well at a current of 600 mA and temperature of 205 °C.

Stabilization of Ni0/NiII Heterojunctions inside Robust Porous Metal Silicate Materials for High-Performance Catalysis.

Heterostructural nanomaterials demonstrate great potential to replace noble metal-based catalysts because heterojunctions could induce relocalization of electrons and facilitate the migration of electrons and charge carriers at the heterostructural boundary between electron-rich and electron-deficient metal sites; however, the instability of heterojunctions greatly hinders their practical applications. We report herein an effective strategy for the fabrication and stabilization of Ni0/NiII heterojunctions inside a porous metal silicate (PMS) material PMS-22 using a nickel coordination complex as the bifunctional template. The synergistic activity between metallic nickel and nickel silicate in PMS-22 highly boosts the catalytic activity in the hydrogenation of phenol, which could activate phenol at a very low temperature of 50 °C. Most importantly, PMS-22 demonstrates robust stability in catalysis, attributed to the strong interaction and charge transfer between metallic Ni and nickel silicate at the heterointerfaces inside the confined pores. Therefore, this work paves a new pathway to improve the stability and activity of heterostructural nanomaterials for catalytic applications.

Transformation of metal-organic frameworks with retained networks.

Metal-organic frameworks (MOFs) are a class of crystalline porous coordination materials with systematically designable network structures and tunable properties, demonstrating great potential for applications in diverse fields. However, the generally poor stability of dynamic coordination bonds in MOFs hinders their practical applications in harsh environments. Although MOFs have been used as precursors and templates for the production of various derivatives with enhanced stability via thermal treatment, the extreme thermolytic conditions often destroy the network structures, consequently resulting in obvious decreases in porosity and surface areas with undesired characteristics. This feature article discusses the generally used pathways for the transformation of MOFs and the advanced fabrication methods for the production of various MOF-derived materials. We particularly emphasize the recent progress in the designed strategies for customization and derivation tailoring of MOFs, which could produce MOF-derived functional materials with remaining framework skeletons and inherited characteristics (surface area, porosity and properties) of the parent MOFs, exhibiting great promise for practical applications.

ZIF-67 Derivative Decorated MXene for a Highly Integrated Flexible Self-Powered Photodetector.

The rapid development of portable and wearable electronics has promoted the integration of multifunction techniques. Although flexible energy storage systems have been successfully investigated, the compact configuration with photodetector and energy storage components has received less attention. As a new member of the 2D material class, MXene exhibits remarkable electronic and optical properties. Here, through the intentional introduction of ZIF-67 derivatives deposited on the Mo2CTx nanosheets, the synthesized Co-CoOx/NC/Mo2CTx heterostructure not only provided a straightforward pathway for photogenerated electrons to transport but also enhanced the structural stability of Mo2CTx, leading to a high responsivity and short rise/decay time under the illumination of simulated light in the photoelectrochemical (PEC) configuration. The integrated flexible device based on a zinc ion battery and Co-CoOx/NC/Mo2CTx heterostructure shows outstanding photodetection function and retains the intrinsic charge/discharge behaviors, which could monitor 1 day sunlight changes in real time. The paradigm presented here paves the way for realizing the development of miniaturization and multifunction toward next-generation portable and wearable technologies.

Interwrapping Distinct Metal-Organic Frameworks in Dual-MOFs for the Creation of Unique Composite Catalysts.

Incorporating metal nanoparticles (MNPs) inside metal-organic frameworks (MOFs) demonstrates superior catalytic properties in numerous reactions; however, the size and distribution of MNPs could not be well controlled, resulting in low product selectivity in catalysis by undergoing different catalytic reaction pathways. We report herein a facile strategy for integrating lattice-mismatched MOFs together to fabricate homogeneously distributed "dual-MOFs," which are the ideal precursors for the preparation of MNPs@MOFs with unique catalytic properties. As a proof of concept, we successfully synthesize a dual-MOF HKUST-1/ZIF-8 for in situ creation of redox-active Cu NPs inside hierarchical porous ZIF-8 under controlled pyrolytic conditions. Combining the advantages of size-tunable Cu NPs in the molecular sieving matrix of ZIF-8, Cu@ZIF-8 demonstrates high activity and selectivity for transformation of alkynes into alkenes without overhydrogenation, which surpasses most of the catalysts in the literature. Therefore, this work paves a new pathway for developing highly efficient and selective heterogeneous catalysts to produce highly value-added chemicals.

High-Loading Pt Single-Atom Catalyst on CeO2 -Modified Diatomite Support.

Single-atom catalysis has become a new branch in heterogeneous catalysis. Although the naturally produced SiO2 -based materials are abundant and stable, fabrication of single-atom catalysts on such supports with high loading remains as a formidable challenge due to the lack of bonding sites to anchor the isolated metal species. Herein, modifying the diatomite, a kind of pure SiO2 mineral, with CeO2 nanoparticles is demonstrated to increase the defect sites on the support. The enhanced metal-support interaction maintains the atomic dispersion of Pt species with above 1 wt.% loading, exhibiting good performance in the selective hydrogenation of phenylacetylene to styrene.

In situ creation of multi-metallic species inside porous silicate materials with tunable catalytic properties.

Porous metal silicate (PMS) material PMS-11, consisting of uniformly distributed multi-metallic species inside the pores, is synthesized by using a discrete multi-metal coordination complex as the template, demonstrating high catalytic activity and selectivity in hydrogenation of halogenated nitrobenzenes by synergistically activating different reactant molecules via Ni and Co transition metal centers, while GdIII Lewis acid sites play a role in tuning the catalytic properties.

Photocatalytic Hydrogen Evolution Coupled with Production of Highly Value-Added Organic Chemicals by a Composite Photocatalyst CdIn2 S4 @MIL-53-SO3 Ni1/2.

Photocatalytic water splitting coupled with the production of highly value-added organic chemicals is of significant importance, which represents a very promising pathway for transforming green solar energy into chemical energy. Herein, we report a composite photocatalyst CdIn2 S4 @MIL-53-SO3 Ni1/2 , which is highly efficient on prompting water splitting for the production of H2 in the reduction half-reaction and selective oxidation of organic molecules for the production of highly value-added organic chemicals in the oxidation half-reaction under visible light irradiation. The superior photocatalytic properties of the composite photocatalyst CdIn2 S4 @MIL-53-SO3 Ni1/2 should be ascribed to coating suspended ion catalyst (SIC), consisting of redox-active NiII ions in the anionic pores of coordination network MIL-53-SO3 - , on the surface of photoactive CdIn2 S4 , which endows photogenerated electron-hole pairs separate more efficiently for high rate production of H2 and selective production of highly value-added organic products, demonstrating great potential for practical applications.

Passing the framework skeleton and properties of coordination materials onto organic framework materials.

A practically applicable strategy for transforming fragile metal-organic frameworks (MOFs) into highly stable and ordered organic framework materials (OFMs) is developed by replacing the labile coordination bonds in MOFs with stable covalent bonds in OFMs, which exhibit hypothetically approximated topology, porosity and properties of the parent MOFs by merging the advantages of MOFs and porous organic materials, thus providing a general pathway for the synthesis of highly ordered OFMs with merged advantages of MOFs and organic polymers.

Tuning the pore structures and photocatalytic properties of a 2D covalent organic framework with multi-branched photoactive moieties.

In this study, a new strategy to establish a 3D local connection of building synthons and tune the functionalities of 2D covalent organic frameworks (COFs) was developed via in situ incorporation of multi-branched building blocks during the synthesis of COFs. The new COF material CPF-3 retains the features including surface area, crystallinity and stability of the pristine 2D COF COF-LZU1 and expands the light absorption range to the visible-light region via incorporation of accessible photoactive porphyrin sites with the 3D local connection. The Sn(iv)-metalated COF material Sn-CPF-3 exhibits high photocatalytic efficiency and selectivity in aerobic oxidation of sulfides to produce highly value-added sulfoxides with up to 23 334 turnovers and 648 h-1 turnover frequency under visible light irradiation.

Modular synthesis of α-aryl ß-perfluoroalkyl ketones via N-heterocyclic carbene catalysis.

A new general de novo synthesis of pharmaceutically important α-aryl ß-perfluoroalkyl ketones has been disclosed. Compared with trifluoromethylation-initiated radical 1,2-aryl migration of α,α-diaryl allylic alcohols, this protocol employs a new strategy of biomimetic carbene catalysis to assemble alkene, aldehyde and perfluoroalkyl reagents, providing access to products with excellent flexibility of the aryl unit and perfluoroalkyl group. This method also demonstrates excellent functional group compatibility, including some Grignard reagent sensitive groups.

The crucial roles of guest water in a biocompatible coordination network in the catalytic ring-opening polymerization of cyclic esters: a new mechanistic perspective.

The ring-opening polymerization (ROP) of cyclic esters/carbonates is a crucial approach for the synthesis of biocompatible and biodegradable polyesters. Even though numerous efficient ROP catalysts have been well established, their toxicity heavily limits the biomedical applications of polyester products. To solve the toxicity issues relating to ROP catalysts, we report herein a biocompatible coordination network, CZU-1, consisting of Zn4(µ4-O)(COO)6 secondary building units (SBUs), biomedicine-relevant organic linkers and guest water, which demonstrates high potential for use in the catalytic ROP synthesis of biomedicine-applicable polyesters. Both experimental and computational results reveal that the guest water in CZU-1 plays crucial roles in the activation of the Zn4(µ4-O)(COO)6 SBUs by generating µ4-OH Brønsted acid centers and Zn-OH Lewis acid centers, having a synergistic effect on the catalytic ROP of cyclic esters. Different to the mechanism reported in the literature, we propose a new reaction pathway for the catalytic ROP reaction, which has been confirmed using density functional theory (DFT) calculations, in situ diffuse reflectance IR Fourier transform spectroscopy (DRIFTS), and matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS). Additionally, the hydroxyl end groups allow the polyester products to be easily post-modified with different functional moieties to tune their properties for practical applications. We particularly expect that the proposed catalytic ROP mechanism and the developed catalyst design principle will be generally applicable for the controlled synthesis of biomedicine-applicable polymeric materials.

In Situ Generation and Stabilization of Accessible Cu/Cu2 O Heterojunctions inside Organic Frameworks for Highly Efficient Catalysis.

Heterostructural metal/metal oxides are the very promising substituents of noble-metal catalysts; however, generation and further stabilization of accessible metal/metal oxide heterojunctions are very difficult. A strategy to encapsulate and stabilize Cu/Cu2 O nanojunctions in porous organic frameworks in situ is developed by tuning the acrylate contents in copper-based metal-organic frameworks (Cu-MOFs) and the pyrolytic conditions. The acrylate groups play important roles on improving the polymerization degree of organic frameworks and generating and stabilizing highly dispersed and accessible Cu/Cu2 O heteronanojunctions. As a result, pyrolysis of the MOF ZJU-199, consisting of three acrylates per ligand, generates abundant heterostructural Cu/Cu2 O discrete domains inside porous organic matrices at 350 °C, demonstrating excellent catalytic properties in liquid-phase hydrogenation of furfural into furfuryl alcohol, which are much superior to the non-noble metal-based catalysts.

Synthesis and Catalytic Properties of Porous Metal Silica Materials Templated and Functionalized by Extended Coordination Cages.

A practically applicable strategy is developed to rationally immobilize easily accessed and highly dispersed redox-active metal oxides into porous metal silica (PMS) materials templated and functionalized by porous metal-ligand moieties. On the basis of this strategy, the highly active porous catalyst PMS-1 is successfully targeted for aerobic oxidation of cyclohexane with conversion up to 14.6%, which is much superior to the current industrially adopted catalysts (less than 4% cyclohexane conversion) that use harsh conditions. This promising approach to explore highly active heterogeneous catalysts for inert C-H bond activation should lead to the further discovery of numerous industrially useful catalysts for the oxidation of inert hydrocarbon raw materials.

Facile preparation of biomass lignin-based hydroxyethyl cellulose super-absorbent hydrogel for dye pollutant removal.

The severe preparation process, poor swelling properties and mechanical properties of traditional cellulose and polyvinyl alcohol (PVA) composite hydrogels heavily limited their practical applications. To solve these issues, we use long-chain hydroxyethyl celluloses (HECs) as framework backbones, short-chain PVAs as branched chains, lignin molecules as extended crosslinkers and epichlorohydrin molecules as crosslinkers to prepare the lignin-based hydroxyethyl cellulose-PVA (LCP) super-absorbent hydrogels in the alkaline aqueous solution under mild reaction conditions, demonstrating high swelling ratio of up to 1220 g/g. The LCP hydrogels could take up large amounts of positively charged dyes rhodamine 6G, crystal violet and methylene blue with uptakes of 153, 184 and 196 mg/g, respectively. The LCP super-absorbent hydrogels also present excellent water retention, biodegradability and excellent swelling properties, which are very promising for applications in the fields of commercial diapers, soil water retention and seed cultivation in agriculture, and dye pollutant removal.

Suspending Ion Electrocatalysts in Charged Metal-Organic Frameworks to Improve the Conductivity and Selectivity in Electroorganic Synthesis.

Electroorganic synthesis is an environmentally friendly alternative to traditional synthetic methods; however, the application of this strategy is heavily hindered by low product selectivity. Metal-organic frameworks (MOFs) exhibit high selectivity in numerous catalytic reactions; however, poor conductivity heavily limits the application of MOFs in electroorganic synthesis. To realize the electrocatalytic application of MOFs in selective electroorganic synthesis, a practically applicable strategy by suspending ion electrocatalysts in charged MOFs is herein reported. This approach could markedly improve the product selectivity in electroorganic synthesis. In the electrocatalytic oxidative self-coupling of benzylamine experiments, the imine product selectivity is markedly improved from 61.3 to 94.9 %, when the MOF-based electrocatalyst is used instead of the corresponding homogeneous electrocatalyst under the identical conditions. Therefore, this work opens a new route to improve the product selectivity in electroorganic synthesis.