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While supported metal nanoparticles (NPs) have shown significant promise in heterogeneous catalysis, precise control over their interaction with the support, which profoundly impacts their catalytic performance, remains a significant challenge. In this study, Pt NPs are incorporated into thioether‐functionalized covalent organic frameworks (denoted COF‐Sx), enabling precise control over the size and electronic state of Pt NPs by adjusting the thioether density dangling on the COF pore walls. Notably, the resulting Pt@COF‐Sx demonstrate exceptional selectivity (> 99 %) in catalytic hydrogenation of p‐chloronitrobenzene to p‐chloroaniline, in sharp contrast to the poor selectivity of Pt NPs embedded in thioether‐free COFs. Furthermore, the conversion over Pt@COF‐Sx exhibits a volcano‐type curve as the thioether density increases, due to the corresponding change of accessible Pt sites. This work provides an effective approach to regulating the catalysis of metal NPs via their microenvironment modulation, with the aid of rational design and precise tailoring of support structure. [ABSTRACT FROM AUTHOR]

A novel class of crystalline porous materials has been developed utilizing multilevel dynamic linkages, including covalent B−O, dative B←N and hydrogen bonds. Typically, boronic acids undergo in situ condensation to afford B3O3‐based units, which further extend to molecular complexes or chains via B←N bonds. The obtained superstructures are subsequently interconnected via hydrogen bonds and π–π interactions, producing crystalline porous organic frameworks (CPOFs). The CPOFs display excellent solution processability, allowing dissolution and subsequent crystallization to their original structures, independent of recrystallization conditions, possibly due to the diverse bond energies of the involved interactions. Significantly, the CPOFs can be synthesized on a gram‐scale using cost‐effective monomers. In addition, the numerous acidic sites endow the CPOFs with high NH3 capacity, surpassing most porous organic materials and commercial materials. [ABSTRACT FROM AUTHOR]

Atomically precise metal nanoclusters (NCs) with unique optical properties and abundant catalytic sites are promising in photocatalysis. However, their light‐induced instability and the difficulty of utilizing the photogenerated carriers for photocatalysis pose significant challenges. Here, MAg24 (M=Ag, Pd, Pt, and Au) NCs doped with diverse single heteroatoms have been encapsulated in a metal–organic framework (MOF), UiO‐66‐NH2, affording MAg24@UiO‐66‐NH2. Strikingly, compared with Ag25@UiO‐66‐NH2, the MAg24@UiO‐66‐NH2 doped with heteroatom exhibits much enhanced activity in photocatalytic hydrogen production, among which AuAg24@UiO‐66‐NH2 presents the best activity up to 3.6 mmol g−1 h−1, far superior to all other counterparts. Moreover, they display excellent photocatalytic recyclability and stability. X‐ray photoelectron spectroscopy and ultrafast transient absorption spectroscopy demonstrate that MAg24 NCs encapsulated into the MOF create a favorable charge transfer pathway, similar to a Z‐scheme heterojunction, when exposed to visible light. This promotes charge separation, along with optimized Ag electronic state, which are responsible for the superior activity in photocatalytic hydrogen production. [ABSTRACT FROM AUTHOR]

Carbon‐based single‐atom catalysts (SACs) have attracted tremendous interest in heterogeneous catalysis. However, the common electric heating techniques to produce carbon‐based SACs usually suffer from prolonged heating time and tedious operations. Herein, a general and facile microwave‐assisted rapid pyrolysis method is developed to afford carbon‐based SACs within 3 min without inert gas protection. The obtained carbon‐based SACs present high porosity and comparable carbonization degree to those obtained by electric heating techniques. Specifically, the single‐atom Ni implanted N‐doped carbon (Ni1−N−C) derived from a Ni‐doped metal–organic framework (Ni‐ZIF‐8) exhibits remarkable CO Faradaic efficiency (96 %) with a substantial CO partial current density (jCO) up to 1.06 A/cm2 in CO2 electroreduction, far superior to the counterpart obtained by traditional pyrolysis with electric heating. Mechanism investigations reveal that the resulting Ni1−N−C presents abundant defective sites and mesoporous structure, greatly facilitating CO2 adsorption and mass transfer. This work establishes a versatile approach to rapid and large‐scale synthesis of SACs as well as other carbon‐based materials for efficient catalysis. [ABSTRACT FROM AUTHOR]

Singlet oxygen (1O2) is ubiquitously involved in various photocatalytic oxidation reactions; however, efficient and selective production of 1O2 is still challenging. Herein, we reported the synthesis of nickel porphyrin‐based covalent organic frameworks (COFs) incorporating functional groups with different electron‐donating/‐withdrawing features on their pore walls. These functional groups established a dedicated outer‐sphere microenvironment surrounding the Ni catalytic center that tunes the activity of the COFs for 1O2‐mediated thioether oxidation. With the increase of the electron‐donating ability of functional groups, the modulated outer‐sphere microenvironment turns on the catalytic activity from a yield of nearly zero by the cyano group functionalized COF to an excellent yield of 98 % by the methoxy group functionalized one. Electronic property investigation and density‐functional theory (DFT) calculations suggested that the distinct excitonic behaviors attributed to the diverse band energy levels and orbital compositions are responsible for the different activities. This study represents the first regulation of generating reactive oxygen species (ROS) based on the strategy of outer‐sphere microenvironment modulation in COFs. [ABSTRACT FROM AUTHOR]

Photocatalytic water splitting and carbon dioxide (CO2) reduction provide promising solutions to global energy and environmental issues. In recent years, metal‐organic frameworks (MOFs), a class of crystalline porous solids featuring well‐defined and tailorable structures as well as high surface areas, have captured great interest toward photocatalytic water splitting and CO2 reduction. In this review, the semiconductor‐like behavior of MOFs is first discussed. We then summarize the recent advances in photocatalytic water splitting and CO2 reduction over MOF‐based materials and focus on the unique advantage of MOFs for clarifying the structure‐property relationship in photocatalysis. In addition, some representative characterization techniques have been presented to unveil the photocatalytic kinetics and reaction intermediates in MOF‐based systems. Finally, the challenges, and perspectives for future directions are proposed. [ABSTRACT FROM AUTHOR]

CO2 hydrogenation to methanol has attracted great interest while suffering from low conversion and high energy input. Herein, tiny Pd3Cu nanoparticles are confined into a metal–organic framework (MOF), UiO‐66, to afford Pd3Cu@UiO‐66 for CO2 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 CO2* promotes CO2 activation and HCOO* formation. In addition, the Pd3Cu microenvironment plays a critical role in CO2 hydrogenation. In contrast to the MOF‐supported Pd3Cu (Pd3Cu/UiO‐66), the Pd3Cu@UiO‐66 exhibits a much higher methanol production rate due to the close proximity between CO2 and H2 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 CO2 hydrogenation under moderate conditions. [ABSTRACT FROM AUTHOR]

Single‐atom catalysts (SACs) have attracted tremendous interests due to their ultrahigh activity and selectivity. However, the rational control over coordination microenvironment of SACs remains a grand challenge. Herein, a post‐synthetic metal substitution (PSMS) strategy has been developed to fabricate single‐atom Ni catalysts with different N coordination numbers (denoted Ni‐Nx‐C) on pre‐designed N‐doped carbon derived from metal‐organic frameworks. When served for CO2 electroreduction, the obtained Ni‐N3‐C catalyst achieves CO Faradaic efficiency (FE) up to 95.6 %, much superior to that of Ni‐N4‐C. Theoretical calculations reveal that the lower Ni coordination number in Ni‐N3‐C can significantly enhance COOH* formation, thereby accelerating CO2 reduction. In addition, Ni‐N3‐C shows excellent performance in Zn–CO2 battery with ultrahigh CO FE and excellent stability. This work opens up a new and general avenue to coordination microenvironment modulation (MEM) of SACs for CO2 utilization. [ABSTRACT FROM AUTHOR]

Single‐atom catalysts (SACs) are of great interest because of their ultrahigh activity and selectivity. However, it is difficult to construct model SACs according to a general synthetic method, and therefore, discerning differences in activity of diverse single‐atom catalysts is not straightforward. Herein, a general strategy for synthesis of single‐atom metals implanted in N‐doped carbon (M1‐N‐C; M=Fe, Co, Ni and Cu) has been developed starting from multivariate metal–organic frameworks (MOFs). The M1‐N‐C catalysts, featuring identical chemical environments and supports, provided an ideal platform for differentiating the activity of single‐atom metal species. When employed in electrocatalytic CO2 reduction, Ni1‐N‐C exhibited a very high CO Faradaic efficiency (FE) up to 96.8 % that far surpassed Fe1‐, Co1‐ and Cu1‐N‐C. Remarkably, the best‐performer, Ni1‐N‐C, even demonstrated excellent CO FE at low CO2 pressures, thereby representing a promising opportunity for the direct use of dilute CO2 feedstock. [ABSTRACT FROM AUTHOR]

The general synthesis and control of the coordination environment of single‐atom catalysts (SACs) remains a great challenge. Herein, a general host–guest cooperative protection strategy has been developed to construct SACs by introducing polypyrrole (PPy) into a bimetallic metal–organic framework. As an example, the introduction of Mg2+ in MgNi‐MOF‐74 extends the distance between adjacent Ni atoms; the PPy guests serve as N source to stabilize the isolated Ni atoms during pyrolysis. As a result, a series of single‐atom Ni catalysts (named NiSA‐Nx‐C) with different N coordination numbers have been fabricated by controlling the pyrolysis temperature. Significantly, the NiSA‐N2‐C catalyst, with the lowest N coordination number, achieves high CO Faradaic efficiency (98 %) and turnover frequency (1622 h−1), far superior to those of NiSA‐N3‐C and NiSA‐N4‐C, in electrocatalytic CO2 reduction. Theoretical calculations reveal that the low N coordination number of single‐atom Ni sites in NiSA‐N2‐C is favorable to the formation of COOH* intermediate and thus accounts for its superior activity. [ABSTRACT FROM AUTHOR]

Abstract: A wide range of light absorption and rapid electron–hole separation are desired for efficient photocatalysis. Herein, on the basis of a semiconductor‐like metal–organic framework (MOF), a Pt@MOF/Au catalyst with two types of metal–MOF interfaces integrates the surface plasmon resonance excitation of Au nanorods with a Pt‐MOF Schottky junction, which not only extends the light absorption of the MOF from the UV to the visible region but also greatly accelerates charge transfer. The spatial separation of Pt and Au particles by the MOF further steers the formation of charge flow and expedites the charge migration. As a result, the Pt@MOF/Au presents an exceptionally high photocatalytic H2 production rate by water splitting under visible light irradiation, far superior to Pt/MOF/Au, MOF/Au and other counterparts with similar Pt or Au contents, highlighting the important role of each component and the Pt location in the catalyst. [ABSTRACT FROM AUTHOR]

The pore size enlargement and structural stability have been recognized as two crucial targets, which are rarely achieved together, in the development of metal-organic frameworks (MOFs). Herein, we have developed a versatile modulator-induced defect-formation strategy, in the presence of monocarboxylic acid as a modulator and an insufficient amount of organic ligand, successfully realizing the controllable synthesis of hierarchically porous MOFs (HP-MOFs) with high stability and tailorable pore characters. Remarkably, the integration of high stability and large mesoporous property enables these HP-MOFs to be important porous platforms for applications involving large molecules, especially in catalysis. [ABSTRACT FROM AUTHOR]