Visible-Light-Promoted C3-Sulfenylindoles with Arylsulfonyl Chlorides via Electron Donor-Acceptor Complex.

In this study, we present an efficient approach for the synthesis of 3-sulfenyl indoles through an electron donor-acceptor (EDA) complex-promoted photoreaction. This sulfenylation reaction leverages sulfonyl chlorides as the sulfur source and employs PPh3 as the reductant without the need for any transition-metal catalyst or photocatalyst. At the same time, the relaxation process of the excited EDA complex was theoretically investigated at the method and multiconfiguration second-order perturbation//complete active space self-consistent field/PCM level of theory, which involves the π bond of indoles injecting an electron to the antibonding orbital of the S-Cl bond in arylsulfonyl chlorides.

Anion Modulation of Ag-Imidazole Cuboctahedral Cage Microenvironments for Efficient Electrocatalytic CO2 Reduction.

How to achieve CO2 electroreduction in high efficiency is a current challenge with the mechanism not well understood yet. The metal-organic cages with multiple metal sites, tunable active centers, and well-defined microenvironments may provide a promising catalyst model. Here, we report self-assembly of Ag4L4 type cuboctahedral cages from coordination dynamic Ag+ ion and triangular imidazolyl ligand 1,3,5-tris(1-benzylbenzimidazol-2-yl) benzene (Ag-MOC-X, X= NO3, ClO4, BF4) via anion template effect. Notably, Ag-MOC-NO3 achieves the highest CO faradaic efficiency in pH-universal electrolytes of 86.1%(acidic), 94.1%(neutral) and 95.3% (alkaline), much higher than those of Ag-MOC-ClO4 and Ag-MOC-BF4 with just different counter anions. In situ attenuated total reflection Fourier transform infrared spectroscopy observes formation of vital intermediate *COOH for CO2-to-CO conversion. The density functional theory calculations suggest that the adsorption of CO2 on unsaturated Ag-site is stabilized by C-H⋅⋅⋅O hydrogen-bonding of CO2 in a microenvironment surrounded by three benzimidazole rings, and the activation of CO2 is dependent on the coordination dynamics of Ag-centers modulated by the hosted anions through Ag⋅⋅⋅X interactions. This work offers a supramolecular electrocatalytic strategy based on Ag-coordination geometry and host-guest interaction regulation of MOCs as high-efficient electrocatalysts for CO2 reduction to CO which is a key intermediate in chemical industry process.

Modular Design of Highly Stable Semiconducting Porous Coordination Polymer for Efficient Electrosynthesis of Ammonia.

Developing highly stable porous coordination polymers (PCPs) with integrated electrical conductivity is crucial for advancing our understanding of electrocatalytic mechanisms and the structure-activity relationship of electrocatalysts. However, achieving this goal remains a formidable challenge because of the electrochemical instability observed in most PCPs. Herein, we develop a "modular design" strategy to construct electrochemically stable semiconducting PCP, namely, Fe-pyNDI, which incorporates a chain-type Fe-pyrazole metal cluster and π-stacking column with effective synergistic effects. The three-dimensional electron diffraction (3D ED) technique resolves the precise structure. Both theoretical and experimental investigation confirms that the π-stacking column in Fe-pyNDI can provide an efficient electron transport path and enhance the structural stability of the material. As a result, Fe-pyNDI can serve as an efficient model electrocatalyst for nitrate reduction reaction (NO3RR) to ammonia with a superior ammonia yield of 339.2 µmol h-1 cm-2 (14677 µg h-1 mgcat. -1) and a faradaic efficiency of 87 % at neutral electrolyte, which is comparable to state-of-the-art electrocatalysts. The in-situ X-ray absorption spectroscopy (XAS) reveals that during the reaction, the structure of Fe-pyNDI can be kept, while part of the Fe3+ in Fe-pyNDI was reduced in situ to Fe2+, which serves as the potential active species for NO3RR.

Growth mechanisms and anisotropic softness-dependent conductivity of orientation-controllable metal-organic framework nanofilms.

Conductive metal-organic frameworks (cMOFs) manifest great potential in modern electrical devices due to their porous nature and the ability to conduct charges in a regular network. cMOFs applied in electrical devices normally hybridize with other materials, especially a substrate. Therefore, the precise control of the interface between cMOF and a substrate is particularly crucial. However, the unexplored interface chemistry of cMOFs makes the controlled synthesis and advanced characterization of high-quality thin films, particularly challenging. Herein, we report the development of a simplified synthesis method to grow "face-on" and "edge-on" cMOF nanofilms on substrates, and the establishment of operando characterization methodology using atomic force microscopy and X-ray, thereby demonstrating the relationship between the soft structure of surface-mounted oriented networks and their characteristic conductive functions. As a result, crystallinity of cMOF nanofilms with a thickness down to a few nanometers is obtained, the possible growth mechanisms are proposed, and the interesting anisotropic softness-dependent conducting properties (over 2 orders of magnitude change) of the cMOF are also illustrated.

Fine Pore-Structure Engineering by Ligand Conformational Control of Naphthalene Diimide-Based Semiconducting Porous Coordination Polymers for Efficient Chemiresistive Gas Sensing.

Exploring new porous coordination polymers (PCPs) that have tunable structure and conductivity is attractive but remains challenging. Herein, fine pore structure engineering by ligand conformation control of naphthalene diimide (NDI)-based semiconducting PCPs with π stacking-dependent conductivity tunability is achieved. The π stacking distances and ligand conformation in these isoreticular PCPs were modulated by employing metal centers with different coordination geometries. As a result, three conjugated PCPs (Co-pyNDI, Ni-pyNDI, and Zn-pyNDI) with varying pore structure and conductivity were obtained. Their crystal structures were determined by three-dimensional electron diffraction. The through-space charge transfer and tunable pore structure in these PCPs result in modulated selectivity and sensitivity in gas sensing. Zn-pyNDI can serve as a room-temperature operable chemiresistive sensor selective to acetone.

Correction: Nitroxyl radical-containing flexible porous coordination polymer for controllable size-selective aerobic oxidation of alcohols.

Correction for 'Nitroxyl radical-containing flexible porous coordination polymer for controllable size-selective aerobic oxidation of alcohols' by Ping Wang et al., Chem. Commun., 2022, 58, 9026-9029, https://doi.org/10.1039/D2CC02772K.

Nitroxyl radical-containing flexible porous coordination polymer for controllable size-aelective aerobic oxidation of alcohols.

The ability of flexible porous coordination polymers (PCPs) to change their structure in response to various stimuli has not been exploited in the design of tunable-selectivity catalysts. Herein, we make use of this ability and prepare nitroxyl radical-containing flexible PCP that can reversibly switch between large- and contracted-pore configurations in response to solvent change and thus promote the controllable size-selective aerobic oxidation of alcohols.

Multiscale structural regulation of metal-organic framework nanofilm arrays for efficient oxygen evolution reaction.

Novel MOF nanofilm arrays (NiCoBDC-Fc) were grown on Ni foam via a multiscale structural regulation strategy. The introduction of metal doping and defects regulated the morphology of NiBDC for increasing the exposure of electrochemically active sites and adjusted the electronic structure of the Ni active center, which enhanced the OER performance of NiCoBDC-Fc/NF.

Tailoring the Electronic Structure of an Atomically Dispersed Zinc Electrocatalyst: Coordination Environment Regulation for High Selectivity Oxygen Reduction.

Accurately regulating the selectivity of the oxygen reduction reaction (ORR) is crucial to renewable energy storage and utilization, but challenging. A flexible alteration of ORR pathways on atomically dispersed Zn sites towards high selectivity ORR can be achieved by tailoring the coordination environment of the catalytic centers. The atomically dispersed Zn catalysts with unique O- and C-coordination structure (ZnO3 C) or N-coordination structure (ZnN4 ) can be prepared by varying the functional groups of corresponding MOF precursors. The coordination environment of as-prepared atomically dispersed Zn catalysts was confirmed by X-ray absorption fine structure (XAFs). Notably, the ZnN4 catalyst processes a 4 e- ORR pathway to generate H2 O. However, controllably tailoring the coordination environment of atomically dispersed Zn sites, ZnO3 C catalyst processes a 2 e- ORR pathway to generate H2 O2 with a near zero overpotential and high selectivity in 0.1 M KOH. Calculations reveal that decreased electron density around Zn in ZnO3 C lowers the d-band center of Zn, thus changing the intermediate adsorption and contributing to the high selectivity towards 2 e- ORR.

Concluding remarks: current and next generation MOFs.

This paper describes the content of my "Concluding remarks" talk at the Faraday Discussion meeting on "MOFs for energy and the environment" (online, 23-25 June 2021). The panel consisted of sessions on the design of MOFs and MOF hybrids (synthetic chemistry), their applications (e.g., capture, storage, separation, electrical devices, photocatalysis), advanced characterization (e.g., transmission electron microscopy, solid-state nuclear magnetic resonance), theory and modeling, and commercialization. MOF chemistry is undergoing a significant evolution from simply network chemistry to the chemistry of synergistic integration with heterogeneous materials involving other disciplines (we call this the fourth generation type). As reflected in the papers of the invited speakers and discussions with the participants, the present and future of this field will be described in detail.

Modulating electronic structure of metal-organic frameworks by introducing atomically dispersed Ru for efficient hydrogen evolution.

Developing high-performance electrocatalysts toward hydrogen evolution reaction is important for clean and sustainable hydrogen energy, yet still challenging. Herein, we report a single-atom strategy to construct excellent metal-organic frameworks (MOFs) hydrogen evolution reaction electrocatalyst (NiRu0.13-BDC) by introducing atomically dispersed Ru. Significantly, the obtained NiRu0.13-BDC exhibits outstanding hydrogen evolution activity in all pH, especially with a low overpotential of 36 mV at a current density of 10 mA cm-2 in 1 M phosphate buffered saline solution, which is comparable to commercial Pt/C. X-ray absorption fine structures and the density functional theory calculations reveal that introducing Ru single-atom can modulate electronic structure of metal center in the MOF, leading to the optimization of binding strength for H2O and H*, and the enhancement of HER performance. This work establishes single-atom strategy as an efficient approach to modulate electronic structure of MOFs for catalyst design.

Interfacial Charge Transfer in a Hierarchical Ni2P/FeOOH Heterojunction Facilitates Electrocatalytic Oxygen Evolution.

The construction of a heterojunction is an important strategy to develop efficient electrocatalysts. However, the precise design and preparation of the heterojunction with desirable catalytic performance remain a challenge. Herein, a hierarchical Ni2P/FeOOH Schottky junction supported on nickel foam was prepared by electrodeposition of FeOOH on the surface of Ni2P. The electrocatalytic activity of the Ni2P/FeOOH Schottky junction can be remarkably improved, owing to the unique hierarchical architecture and strong electron interaction in the Ni2P/FeOOH Schottky junction. As-prepared Ni2P/FeOOH exhibits excellent electrocatalytic activity for an oxygen evolution reaction (OER) with an ultralow overpotential of 246 mV to reach 100 mA cm-2 and a small Tafel slope of 62.8 mV dec-1. This work provides not only a new method for the design of hierarchical nanomaterials but also an efficient strategy to design efficient OER electrocatalysts by constructing hierarchical heterojunctions.

Erratum: One-Step Construction of Hydrophobic MOFs@COFs Core-Shell Composites for Heterogeneous Selective Catalysis.

[This corrects the article DOI: 10.1002/advs.201802365.].

Hierarchical Nanorods of MoS2 /MoP Heterojunction for Efficient Electrocatalytic Hydrogen Evolution Reaction.

Hierarchical nanostructures with tailored component and architectures are attractive for energy-related applications. Here, the delicate design and construction of hierarchical MoS2 /MoP (H-MoS2 /MoP) nanorods for the hydrogen evolution reaction (HER) are demonstrated. This multiscale design rationally combines the compositional and structural advantages of MoS2 /MoP heterojunction into a hierarchical architecture, which can modulate electronic structure of S, remarkably facilitating the electrocatalytic HER. Benefitting from their unique architecture and electronic structure, the H-MoS2 /MoP nanorods exhibit excellent performance for HER with ultralow overpotential of 92 mV at current density of 10 mA cm-2 in 1 m KOH and high stability. This work not only provides an efficient approach to constructing hierarchical heterojunctions, but also a multiscale strategy for all-round regulation of the electronic structure and hierarchical morphology of nanomaterials for energy-related applications.

Trimetallic MOF-74 Films Grown on Ni Foam as Bifunctional Electrocatalysts for Overall Water Splitting.

Developing earth-abundant and high-performance electrocatalysts for water splitting has long been a vital research in energy conversion field. Herein, we report the preparation of a series of trimetallic uniform Mnx Fey Ni-MOF-74 films in-situ grown on nickel foam, which can be utilized as bifunctional electrocatalysts towards overall water splitting in alkaline media. The introduction of Mn can simultaneously regulate the morphology of MOF-74 to form uniform film and modulate electronic structure of Fe to form more Fe(II)-O-Fe(III) motifs, which is conducive to the exposure of active sites and stabilizing high-valent metal sites. The optimized Mn0.52 Fe0.71 Ni-MOF-74 film electrode showed excellent electrocatalytic performance, affording a current density of 10 mA ⋅ cm-2 at an overpotential of 99 mV for HER and 100 mA ⋅ cm-2 at an overpotential of 267 mV for OER, respectively. Assembled as an electrolyser, Mn0.52 Fe0.71 Ni-MOF-74 film electrode exhibited excellent performance towards overall water splitting, with ultralow overpotential of 245 and 462 mV to achieve current density of 10 and 100 mA ⋅ cm-2 , respectively. This work provides a new view to develop multi-metal MOF-based electrocatalysts.

Missing-linker metal-organic frameworks for oxygen evolution reaction.

Metal-organic frameworks (MOFs) have been recognized as compelling platforms for the development of miscellaneous applications because of their structural diversity and functional tunability. Here, we propose that the electrocatalytic properties could be well modified by incorporating missing linkers into the MOF. Theoretical calculations suggest the electronic structure of MOFs can be tuned by introducing missing linkers, which improves oxygen evolution reaction (OER) performance of the MOF. Inspired by these aspects, we introduced various missing linkers into a layered-pillared MOF Co2(OH)2(C8H4O4) (termed as CoBDC) to prepare missing-linker MOFs. Transmission electron microscope and synchrotron X-ray measurements confirmed that the missing linkers in the MOF could be introduced and well controlled by our strategy. The self-supported MOF nanoarrays with missing linkers of carboxyferrocene exhibit excellent OER performance with ultralow overpotential of 241 mV at 100 mA cm-2. This work opens a new prospect to develop efficient MOF-based electrocatalysts by introducing missing linkers.

One-Step Construction of Hydrophobic MOFs@COFs Core-Shell Composites for Heterogeneous Selective Catalysis.

The exploration of novel porous core-shell materials is of great significance because of their prospectively improved performance and extensive applications in separation, energy conversion, and catalysis. Here, mesoporous metal-organic frameworks (MOFs) NH2-MIL-101(Fe) as a core generate a shell with mesoporous covalent organic frameworks (COFs) NUT-COF-1(NTU) by a covalent linking process, the composite NH2-MIL-101(Fe)@NTU keeping retentive crystallinity with hierarchical porosity well. Importantly, the NH2-MIL-101(Fe)@NTU composite shows significantly enhanced catalytic conversion and selectivity during styrene oxidation. It is mainly due to the hydrophilic MOF nanocrystals readily gathering the hydrophobic reactants styrene and boosting the radical mechanism path after combining the hydrophobic COFs shell. The synthetic strategy in this systematic study develops a new rational design for the synthesis of other core-shell MOF/COF-based hybrid materials, which can expand the promising applications.

Interfacial Electronic Structure Modulation of NiTe Nanoarrays with NiS Nanodots Facilitates Electrocatalytic Oxygen Evolution.

Interface engineering has been recognized as one of the most promising strategies for regulating the physical and chemical properties of materials. However, constructing well-defined nanointerfaces with efficient oxygen evolution reaction (OER) still remains a challenge. Herein, cross columnar NiTe nanoarrays supported on nickel foam are prepared. Subsequently, NiTe/NiS nanointerfaces are constructed by an ion-exchange process. Importantly, the electrocatalytic performance for the OER can be facilitated by coupling NiTe and NiS. As a result, NiTe/NiS shows excellent OER activity with an ultralow overpotential of only 257 mV at a current density of 100 mA cm-2 , and a Tafel slope of 49 mV dec-1 in 1.0 m KOH. The calculated and experimental results reveal that the strong electron interaction on nanointerfaces induces electronic structure modulation, which optimizes the binding energy of *OOH intermediates, thus improving the OER performance.

MOF-derived Mn doped porous CoP nanosheets as efficient and stable bifunctional electrocatalysts for water splitting.

Searching for highly active and stable bifunctional electrocatalysts for overall water splitting, e.g., for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), is dominating in terms of bringing future renewable energy storage and conversion processes to reality. In this work, a kind of two-dimensional ultrathin manganese (Mn) doped polyhedral cobalt phosphide (Mn-CoP) has been synthesized via the etching-carbonization-phosphidation of Co-centered metal-organic frameworks. The as-prepared porous Mn-CoP nanosheets had a larger specific surface area and higher porosity, furnishing them with more plentiful catalytically active sites than their counterpart hollow CoP and Mn-CoP nanoparticles, and thus showed much better electrocatalytic activity for both HER and OER in acidic and alkaline media. In addition, the Mn-CoP nanosheets also demonstrated excellent durability after long-term operation. These high performances are attributed to the synergistic effects of the CoP nanosheets with intrinsic activity, the graphitic carbon and the controllable electronic structure doped by Mn and N elements. This synthetic methodology of using a classical MOF as a precursor to build a new 2D sheet-like composite may create opportunities to search for highly efficient and robust non-precious metal catalysts for energy-related reactions.

A novel "tunnel-like" cyclopalladated arylimine catalyst immobilized on graphene oxide nano-sheet.

A novel "tunnel-like" cyclopalladated arylimine was prepared and immobilized on graphene oxide nano-sheet to form a hybrid catalytic material (denoted as F-GO-Pd) by self-assembly. The F-GO-Pd catalyst was characterized by XRD, FTIR, Raman, XPS, SEM, and TEM. This novel hybrid catalytic material was proven to be an efficient catalyst for the Suzuki-Miyaura coupling reaction of aryl halides (I, Br, Cl) with arylboronic acids in aqueous media under mild conditions with a very low amount of catalyst (0.01 mol%) and a high turnover frequency (TOF) (>20 000 h-1). In particular, high yields also could be obtained at room temperature with prolonged time. F-GO-Pd also showed good stability and recyclability seven times with a superior catalytic activity. The heterogeneous catalytic mechanism was investigated with kinetic studies, hot filtration tests, catalyst poisoning tests, and in situ FTIR spectroscopy with a ReactIR and the deactivation mechanism of the catalysts was proposed through analysis of its chemical stability by TEM, SEM, Raman, and XRD, indicating that a heterogeneous catalytic process occurred on the surface and the changes of the catalytic activity during the recycling were related to the micro-environment of the catalyst surface.