Single-atom tailored atomically-precise nanoclusters for enhanced electrochemical reduction of CO2-to-CO activity.

The development of facile tailoring approach to adjust the intrinsic activity and stability of atomically-precise metal nanoclusters catalysts is of great interest but remians challenging. Herein, the well-defined Au8 nanoclusters modified by single-atom sites are rationally synthesized via a co-eletropolymerization strategy, in which uniformly dispersed metal nanocluster and single-atom co-entrenched on the poly-carbazole matrix. Systematic characterization and theoretical modeling reveal that functionalizing single-atoms enable altering the electronic structures of Au8 clusters, which amplifies their electrocatalytic reduction of CO2 to CO activity by ~18.07 fold compared to isolated Au8 metal clusters. The rearrangements of the electronic structure not only strengthen the adsorption of the key intermediates *COOH, but also establish a favorable reaction pathway for the CO2 reduction reaction. Moreover, this strategy fixing nanoclusters and single-atoms on cross-linked polymer networks efficiently deduce the performance deactivation caused by agglomeration during the catalytic process. This work contribute to explore the intrinsic activity and stability improvement of metal clusters.

KOH-Enabled Axial-Oxygen Coordinated Ni Single-Atom Catalyst for Efficient Electrocatalytic CO2 Reduction.

Precise control of the coordination structure of metal centers is an ideal approach to achieve reasonable selectivity, activity, and stability in the electrochemical reduction of CO2 . In this work, the KOH activation strategy for preparation of hierarchically porous material containing Ni single-atoms with axial-oxygen coordination is reported. Spectroscopic measurements reveal the multiple roles of KOH as oxygen source, pore-making reagent and promoter for the formation of key phthalocyanine structure. It exhibits superior surface area (1801 m2  g-1 ) and electrocatalytic performance (Faradaic efficiency of 94%, Turnover frequency of 11 362 h-1 ). Notably, KOH-enabled architecture with abundant pores benefits the anchoring of Ni atoms and mass transfer for high activity and selectivity. Density functional theory calculations suggest that the axial-oxygen ligand can promote the electronic delocalization of the Ni site for facilitating the *COOH formation and *CO desorption to efficiently produce CO.

Catalytic Cyanation of C-N Bonds with CO2/NH3.

Cyanation of benzylic C-N bonds is useful in the preparation of important α-aryl nitriles. The first general catalytic cyanation of α-(hetero)aryl amines, analogous to the Sandmeyer reaction of anilines, was developed using reductive cyanation with CO2/NH3. A broad array of α-aryl nitriles was obtained in high yields and regioselectivity by C-N cleavage of intermediates as ammonium salts. Good tolerance of functional groups such as ethers, CF3, F, Cl, esters, indoles, and benzothiophenes was achieved. Using 13CO2, a 13C-labeled tryptamine homologue (five steps, 31% yield) and Cysmethynil (six steps, 37% yield) were synthesized. Both electronic and steric effects of ligands influence the reactivity of alkyl nickel species with electrophilic silyl isocyanates and thus determine the reactivity and selectivity of the cyanation reaction. This work contributes to the understanding of the controllable activation of CO2/NH3 and provides the promising potential of the amine cyanation reaction in the synthesis of bio-relevant molecules.

Recyclable Oxofluorovanadate-Catalyzed Formylation of Amines by Reductive Functionalization of CO2 with Hydrosilanes.

An efficient method has been developed for the reductive amination of CO2 by using readily available and recyclable oxofluorovanadates as catalysts. Various amines are transformed into the desired N-formylated products in moderate to excellent yields at room temperature in the presence of phenylsilane. Mechanistic studies based on in situ infrared spectroscopy suggest a reaction pathway initiated through F-Si interactions. The activated phenylsilane allows for CO2 insertion to produce phenylsilyl formate, which undergoes attack by the amine to generate the target product.

Ru-Catalyzed Switchable N-Hydroxyethylation and N-Acetonylation with Crude Glycerol.

Highly efficient Ru-catalyzed selective C-C or C-O bond cleavage of polyols (e.g., crude glycerol) for N-hydroxyethylation or N-acetonylation of amines was achieved through the hydrogen-borrowing approach. A variety of amines were transformed to the desired amino alcohols/ketones in moderate-to-excellent yields, opening up new avenues for generation of oxygenated pharmaceuticals and fine chemicals from renewable raw materials. The use of new redox-active catalysts containing bisphosphine/thienylmethylamine ligands allows this hydrogen-borrowing system to be operated selectively under both basic and acidic conditions.

Cu14 Cluster with Partial Cu(0) Character: Difference in Electronic Structure from Isostructural Silver Analog.

An atom-precise Cu0-containing copper cluster, Cu14(C2B10H10S2)6(CH3CN)8 (abbreviated as Cu14-8CH3CN) is reported, which is synthesized via a simultaneous reduction strategy and fully characterized by single-crystal X-ray diffraction, ESI-TOF-MS, and X-ray photoelectron spectroscopy. Cu14-8CH3CN is the only copper cluster that has a virtually identical silver structural analog, i.e., Ag14(C2B10H10S2)6(CH3CN)8 (hereafter as Ag14-8CH3CN). Nevertheless, density functional theory calculations reveal that the electronic structure of Cu14-8CH3CN differs significantly from the superatom electronic configuration of Ag14-8CH3CN. Moreover, Cu14-8CH3CN shows room-temperature luminescence and good electrocatalytic activities in the ethanol oxidation reaction and detection of H2O2. This pair of unprecedented analogous molecular nanoscale systems offer an ideal platform to investigate the fundamental differences between copper and silver in terms of catalytic activity and optical properties.

Distinct photophysical properties in atom-precise silver and copper nanocluster analogues.

The synthesis of atom-precise analogues of homometallic nanoclusters remains a great challenge. Herein we report the first pair of atom-precise copper/silver-thiolate halide cluster analogues, namely [Cu17/Ag17I3S(C2B10H10S2)6(CH3CN)11] (Cu17 and Ag17), obtained by bottom-up self-assembly and complete-metal-exchange-induced cluster-to-cluster transformation, respectively. The differences in optical absorption and emission of these analogues were fully elucidated by experimental and theoretical methods.

Amino functionalized Zn/Cd-metal-organic frameworks for selective CO2 adsorption and Knoevenagel condensation reactions.

Two amino functionalized Metal-Organic Frameworks (MOFs), {[Zn(Py2TTz)(2-NH2-BDC)]·(DMF)}n (1) and {[Cd(Py2TTz)(2-NH2-BDC)]·(DMF)·0.5(H2O)}n (2) (where Py2TTz = 2,5-bis(4-pyridyl)thiazolo[5,4-d]thiazole, 2-NH2-BDC = 2-amino-1,4-benzenedicarboxylate, and DMF = N,N-dimethylformamide), were synthesized and characterized using the primary ligand 2-amino-1,4-benzenedicarboxylic acid (2-NH2-H2BDC) and the auxiliary ligand 2,5-bis(4-pyridyl)thiazolo[5,4-d]thiazole (Py2TTz). They possess similar 2-fold interpenetrated three-dimensional bipillared-layer framework structures composed of typical binuclear metal nodes, 2-NH2-BDC two-dimensional layers and Py2TTz bipillars. Notably, thiazole nitrogen atoms and pendant -NH2 groups are present in channels in the two frameworks. Given their good chemical stabilities, high thermal stabilities, and exposed nitrogen sites, gas adsorption and catalytic experiments of the two MOFs were performed. The results demonstrate that MOF 2 can selectively adsorb carbon dioxide gas; moreover, the two MOFs can be employed as recyclable heterogeneous catalysts for Knoevenagel condensation reactions under solvent-free conditions.

Mn-Catalyzed Selective Double and Mono-N-Formylation and N-Methylation of Amines by using CO2.

Functionalization of amines by using CO2 is of fundamental importance considering the abundance of amines and CO2 . In this context, the catalytic formylation and methylation of amines represent convenient and successful protocols for selective CO2 utilization as a C1 building block. This study represents the first example of selective catalytic double N-formylation of aryl amines by using a dinuclear Mn complex in the presence of phenylsilane. This robust system also allows for selective formylation and methylation of amines under a range of conditions.

Photoluminescence modulation of an atomically precise silver(i)-thiolate cluster via site-specific surface engineering.

A series of pyridyl ligand functionalized silver-thiolate nanoclusters with an identical cuboctahedron Ag12 core were prepared through site-specific surface engineering and fully characterized. Their wide-range photoluminescence modulation was systematically studied.

Towards Hydrogen Storage through an Efficient Ruthenium-Catalyzed Dehydrogenation of Formic Acid.

Hydrogen is of fundamental importance for the construction of modern clean-energy supply systems. In this context, the catalytic dehydrogenation of formic acid (FA) is a convenient method to generate H2 gas from an easily available liquid. One of the issues associated with current catalytic dehydrogenation systems is insufficient stability. Here, we present a robust and recyclable system for FA dehydrogenation by combining a ruthenium 1,1,1-tris(diphenylphosphinomethyl)ethane complex and aluminum trifluoromethanesulfonate (Al(OTf)3 ). This robust system allows steady H2 production under pressure and recycling for an additional 14 runs without any apparent loss of activity (turnover frequencies up to 1920 h-1 , turnover numbers up to 20 000). Notably, the catalyst can also be used for the dehydrogenation of formates and the reverse hydrogenation of bicarbonates and CO2 .

Regioselectivity inversion tuned by iron(iii) salts in palladium-catalyzed carbonylations.

Impactful regioselectivity control is crucial for cost-effective chemical synthesis. By using cheap and abundant iron(iii) salts, the hydroxycarbonylations of both aromatic and aliphatic alkenes were significantly enhanced in both reactivity and selectivity (iso/n or n/iso up to >99 : 1). Moreover, Pd-catalyzed carbonylation selectivity can be switched from branched to linear by using different Fe(iii) salts. In addition, similar results were obtained for the carbonylation of secondary alcohols.

Hypersensitive dual-function luminescence switching of a silver-chalcogenolate cluster-based metal-organic framework.

Silver(i) chalcogenide/chalcogenolate clusters are promising photofunctional materials for sensing, optoelectronics and solar energy harvesting applications. However, their instability and poor room-temperature luminescent quantum yields have hampered more extensive study. Here, we graft such clusters to adaptable bridging ligands, enabling their interconnection and the formation of rigid metal-organic frameworks. By controlling the spatial separation and orientation of the clusters, they then exhibit enhanced stability (over one year) and quantum yield (12.1%). Ultrafast dual-function fluorescence switching (<1 s) is also achieved, with turn-off triggered by O2 and multicoloured turn-on by volatile organic compounds. Single-crystal X-ray diffraction of the inclusion materials, obtained by single-crystal-to-single-crystal transformation, enables precise determination of the position of the small molecules within the framework, elucidating the switching mechanism. The work enriches the cluster-based metal-organic framework portfolio, bridges the gap between silver chalcogenide/chalcogenolate clusters and metal-organic frameworks, and provides a foundation for further development of functional silver-cluster-based materials.

Hierarchical assembly of a homochiral triple concentric helical system in a novel 3D supramolecular metal-organic framework: synthesis, crystal structure, and SHG properties.

The hierarchical assembly of a homochiral triple concentric helical system in a novel 3D metal-organic framework with SHG activity has been observed. The result also provides a better understanding of host-guest chemistry and the process of water transport in biological systems.

Syntheses, structures and properties of two unusual silver-organic coordination networks: 1D→1D tubular intertwinement and existence of an infinite winding water chain.

Two unusual metal-organic frameworks {[Ag(2)(Hbtc)(bpy)(2)]·(H(2)O)(2)}(n) (1), {[Ag(3)(btc)(bpy)(3)(H(2)O)]·(H(2)O)(7)}(n) (2) (H(3)btc = 1,2,3-benzenetricarboxylic acid, bpy = 4,4'-bipyridine) have been synthesized and characterized by single crystal X-ray diffraction. Complex 1 features an infinite 1D→1D tubular intertwinement network, while complex 2 exhibits a double ladder structure which contains rare winding water chains. Both infinite 1D→1D tubular chains in complex 1 and double ladder in 2 are mutually interconnected by hydrogen bonding and π···π stacking interactions into three-dimensional (3D) supramolecular networks. In addition, thermogravimetric analysis, powder X-ray diffraction (XRD), and photoluminescent behavior of the complexes have also been investigated.

Diaquabis[2'-(4,5-diazafluoren-9-ylidene)picolinohydrazidato-kappa2N,O]zinc(II) tetrahydrate: a metal-water chain complex containing cyclic water hexamers.

In the title compound, [Zn(C17H10N5O)2(H2O)2].4H2O, cyclic water hexamers forming one-dimensional metal-water chains are observed. The water clusters are trapped by the co-operative association of coordination interactions and hydrogen bonds. The ZnII ion resides on a centre of symmetry and is in an octahedral coordination environment comprising two O atoms and two N atoms from two 2'-(4,5-diazafluoren-9-ylidene)picolinohydrazidate ligands and two water molecules.