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The electrocatalytic reaction pathway is highly dependent on the intrinsic structure of the catalyst. CO 2 /CO electroreduction has recently emerged as a potential approach for obtaining C 2+ products, but it is challenging to achieve high selectivity for a single C 2+ product. Herein, we develop a Cu atomic ensemble that satisfies the appropriate site distance and coordination environment required for electrocatalytic CO-to-acetate conversion, which shows outstanding overall performance with an acetate Faradaic efficiency of 70.2% with a partial current density of 225 mA cm -2 and a formation rate of 2.1 mmol h -1 cm -2 . Moreover, a single-pass CO conversion rate of 91% and remarkable stability can be also obtained. Detailed experimental and theoretical investigations confirm the significant advantages of the Cu atomic ensembles in optimizing C-C coupling, stabilizing key ketene intermediate (*CCO), and inhibiting the *HOCCOH intermediate, which can switch the CO reduction pathway from the ethanol/ethylene on the conventional metallic Cu site to the acetate on the Cu atomic ensembles.

Selective removal of the nitrogen atom from an aromatic N -heterocycle, such as pyridine, is of significant interest and importance, yet it remains highly challenging. Here, we report an unprecedented denitrogenative ring-contraction reaction of pyridines at a dititanium hydride framework, yielding cyclopentadienyl and nitride species under mild conditions. The reaction of pyridine with a dititanium tetrahydride complex ( 1 ) bearing rigid acridane-based PNP-pincer ligands at room temperature produced a cyclopentadienyl/nitride complex ( 2 ), in which the two Ti atoms are bridged by a nitride atom and one Ti atom is bonded to a cyclopentadienyl group formed by pyridine denitrogenation and ring-contraction. The reactions of 2-, 3-, and 4-methylpyridines with 1 under similar conditions yielded the same product ( 3 ), a methylcyclopentadienyl-ligated analog of 2 . When 2,4- or 3,5-dimethylpyridine reacted with 1 at 60 °C, the 1,3-dimethylcyclopentadienyl-ligated analog ( 5 ) formed almost quantitatively. The mechanistic details have been elucidated by isolation of key intermediates and density functional theory calculations. It was revealed that the reaction proceeded via coordination of the N atom of a pyridine unit to a Ti atom in 1 followed by H 2 release, C═N reduction, two C-N bond cleavage (ring-opening and denitrogenation), and C-C coupling (ring closing). The involvement of C-H activation in an isopropyl group of a PNP ligand at the later stages of the reaction significantly contributed to the stabilization of the denitrogenative ring-contraction product. This work not only provides unprecedented mechanistic insights into denitrogenation of aromatic N -heterocycles but also represents a novel example of skeletal editing of aromatic N -heterocycles.

Rational regulation of the electrochemical CO 2 reduction reaction (CO 2 RR) pathway to produce desired products is particularly interesting, yet designing economical and robust catalysts is crucial. Here, we report an antimony-modified copper (CuSb) catalyst capable of selectively producing both CO and multicarbon (C 2+ ) products in the CO 2 RR. At a current density of 0.3 A/cm 2 , the faradaic efficiency (FE) of CO was as high as 98.2% with a potential of -0.6 V vs reversible hydrogen electrode (RHE). When the current density increased to 1.1 A/cm 2 at -1.1 V vs RHE, the primary products shifted to C 2+ compounds with a FE of 75.6%. Experimental and theoretical studies indicate that tuning the potential could manipulate the oxygen species on the CuSb surface, which determined the product selectivity in the CO 2 RR. At a more positive potential, the existence of oxygen species facilitates the potential-limiting step involving *COOH formation and reduces the adsorption of *CO intermediates, thereby promoting CO production. At a more negative potential, the localized high CO concentration coupled with the enhanced adsorption of *CO intermediates due to Sb incorporation facilitates C-C coupling and deep hydrogenation processes, resulting in an increased C 2+ selectivity.

Electrocatalytic coupling of CO 2 and NO 3 - to urea is a promising way to mitigate greenhouse gas emissions, reduce waste from industrial processes, and store renewable energy. However, the poor selectivity and activity limit its application due to the multistep process involving diverse reactants and reactions. Herein, we report the first work to design heterostructured Cu-Bi bimetallic catalysts for urea electrosynthesis. A high urea Faradaic efficiency (FE) of 23.5% with a production rate of 2180.3 μg h -1 mg cat -1 was achieved in H-cells, which surpassed most reported electrocatalysts in the literature. Moreover, the catalyst had a remarkable recycling stability. Experiments and density functional theory calculations demonstrated that introduction of moderate Bi induced the formation of the Bi-Cu/O-Bi/Cu 2 O heterostructure with abundant phase boundaries, which are beneficial for NO 3 - , CO 2 , and H 2 O activation and enhance C-N coupling and promote *HONCON intermediate formation. Moreover, favorable *HNCONH 2 protonation and urea desorption processes were also validated, further explaining the reason for high activity and selectivity toward urea.

Analyzing the molecular structure-photophysical property correlations of metal nanoclusters to accomplish function-oriented photocatalysis could be challenging. Here, the selective heteroatom alloying has been exploited to a Au 15 nanocluster, making up a structure-correlated nanocluster series, including homogold Au 15 , bimetallic Ag x Au 15- x and Cu x Au 15- x , trimetallic Ag x Cu y Au 15- x - y , and tetrametallic Pt 1 Ag x Cu y Au 15- x - y . Their structure-dependent photophysical properties were investigated due to the atomically precise structures of these nanoclusters. Cu-alloyed Cu x Au 15- x showed intense phosphorescence and the highest singlet oxygen production efficiency. Moreover, the generation of 1 O 2 species from excited nanoclusters enabled Cu x Au 15- x as a suitable catalyst for efficient photocatalytic oxidation of silyl enol ethers to produce α,β-unsaturated carbonyl compounds. The generality and applicability of the Cu x Au 15- x catalysts toward different photocatalytic oxidations were assessed. Overall, this study presents an intriguing Au 15 -based cluster series enabling an atomic-level understanding of structure-photophysical property correlations, which hopefully provides guidance for the fabrication of cluster-based catalysts with customized photocatalytic performance.

The development of luminescent materials via mechanochemistry embodies a compelling yet intricate frontier within materials science. Herein, we delineate a methodology for the synthesis of brightly luminescent polymers, achieved by the mechanochemical coupling of aggregation-induced emission (AIE) prefluorophores with generic polymers. An array of AIE moieties tethered to the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical are synthesized as prefluorophores, which initially exhibit weak fluorescence due to intramolecular quenching. Remarkably, the mechanical coupling of these prefluorophores with macromolecular radicals, engendered through ball milling of generic polymers, leads to substantial augmentation of fluorescence within the resultant polymers. We meticulously evaluate the tunable emission of the AIE-modified polymers, encompassing an extensive spectrum from the visible to the near-infrared region. This study elucidates the potential of such materials in stimuli-responsive systems with a focus on information storage and encryption displays. By circumventing the complexity inherent to the conventional synthesis of luminescent polymers, this approach contributes a paradigm to the field of AIE-based polymers with implications for advanced technological applications.

Cu-based catalysts are optimal for the electroreduction of CO 2 to generate hydrocarbon products. However, controlling product distribution remains a challenging topic. The theoretical investigations have revealed that the coordination number (CN) of Cu considerably influences the adsorption energy of *CO intermediates, thereby affecting the reaction pathway. Cu catalysts with different CNs were fabricated by reducing CuO precursors via cyclic voltammetry (Cyc-Cu), potentiostatic electrolysis (Pot-Cu), and pulsed electrolysis (Pul-Cu), respectively. High-CN Cu catalysts predominantly generate C 2+ products, while low-CN Cu favors CH 4 production. For instance, over the high-CN Pot-Cu, C 2+ is the main product, with the Faradaic efficiency (FE) reaching 82.5% and a partial current density ( j ) of 514.3 mA cm -2 . Conversely, the low-CN Pul(3)-Cu favors the production of CH 4 , achieving the highest FE CH4 value of 56.7% with a j CH4 . In situ X-ray absorption spectroscopy and Raman spectroscopy studies further confirm the different *CO adsorptions over Cu catalysts with different CN, thereby directing the reaction pathway of the CO -2 . In situ X-ray absorption spectroscopy and Raman spectroscopy studies further confirm the different *CO adsorptions over Cu catalysts with different CN, thereby directing the reaction pathway of the CO 2 RR.

The complex and dynamic compositions of biofilms, along with their sophisticated structural assembly mechanisms, endow them with exceptional capabilities to thrive in diverse conditions that are typically unfavorable for individual cells. Characterizing biofilms in their native state is significantly challenging due to their intrinsic complexities and the limited availability of noninvasive techniques. Here, we utilized solid-state nuclear magnetic resonance (NMR) spectroscopy to analyze Bacillus subtilis biofilms in-depth. Our data uncover a dynamically distinct organization within the biofilm: a dominant, hydrophilic, and mobile framework interspersed with minor, rigid cores of limited water accessibility. In these heterogeneous rigid cores, the major components are largely self-assembled. TasA fibers, the most robust elements, further provide a degree of mechanical support for the cell aggregates and some lipid vesicles. Notably, rigid cell aggregates can persist even without the major extracellular polymeric substance (EPS) polymers, although this leads to slight variations in their rigidity and water accessibility. Exopolysaccharides are exclusively present in the mobile domain, playing a pivotal role in its water retention property. Specifically, all water molecules are tightly bound within the biofilm matrix. These findings reveal a dual-layered defensive strategy within the biofilm: a diffusion barrier through limited water mobility in the mobile phase and a physical barrier posed by limited water accessibility in the rigid phase. Complementing these discoveries, our comprehensive, in situ compositional analysis is not only essential for delineating the sophisticated biofilm architecture but also reveals the presence of alternative genetic mechanisms for synthesizing exopolysaccharides beyond the known pathway.

Hydroxylamine (HA, NH 2 OH) is a critical feedstock in the production of various chemicals and materials, and its efficient and sustainable synthesis is of great importance. Electroreduction of nitrate on Cu-based catalysts has emerged as a promising approach for green ammonia (NH 3 ) production, but the electrosynthesis of HA remains challenging due to overreduction of HA to NH 3 . Herein, we report the first work on ketone-mediated HA synthesis using nitrate in water. A metal-organic-framework-derived Cu catalyst was developed to catalyze the reaction. Cyclopentanone (CP) was used to capture HA in situ to form CP oxime (CP-O) with C═N bonds, which is prone to hydrolysis. HA could be released easily after electrolysis, and CP was regenerated. It was demonstrated that CP-O could be formed with an excellent Faradaic efficiency of 47.8%, a corresponding formation rate of 34.9 mg h -1 cm -2 , and a remarkable carbon selectivity of >99.9%. The hydrolysis of CP-O to release HA and CP regeneration was also optimized, resulting in 96.1 mmol L -1 of HA stabilized in the solution, which was significantly higher than direct nitrate reduction. Detailed in situ characterizations, control experiments, and theoretical calculations revealed the catalyst surface reconstruction and reaction mechanism, which showed that the coexistence of Cu 0 and Cu + facilitated the protonation and reduction of *NO 2 and *NH 2 OH desorption, leading to the enhancement for HA production.

Glycine is a nonessential amino acid that plays a vital role in various biological activities. However, the conventional synthesis of glycine requires sophisticated procedures or toxic feedstocks. Herein, we report an electrochemical pathway for glycine synthesis via the reductive coupling of oxalic acid and nitrate or nitrogen oxides over atomically dispersed Fe-N-C catalysts. A glycine selectivity of 70.7% is achieved over Fe-N-C-700 at -1.0 V versus RHE. Synergy between the FeN 3 C structure and pyrrolic nitrogen in Fe-N-C-700 facilitates the reduction of oxalic acid to glyoxylic acid, which is crucial for producing glyoxylic acid oxime and glycine, and the FeN 3 C structure could reduce the energy barrier of *HOOCCH 2 NH 2 intermediate formation thus accelerating the glyoxylic acid oxime conversion to glycine. This new synthesis approach for value-added chemicals using simple carbon and nitrogen sources could provide sustainable routes for organonitrogen compound production.

Although a variety of chiral porous framework materials have been reported, there are few examples known to combine molecular chirality, helicity, and three-dimensional (3D) intrinsically chiral topology in one structure, which is beneficial for chirality transfer and amplification. Here, we report the synthesis of the first two 3D covalent organic frameworks (COFs) with an intrinsic chiral qzd topology, which exhibit unusual integration of various homochiral and homohelical features. By imine condensation of 4-connected porphyrin tetraamines and 2-connected enantiopure diene dialdehyde, we prepared two isostructural COFs with a noninterpenetrated qzd topology. The specific geometry and conformation flexibility of the V-shaped diene linker control the alignment of square-planar porphyrin units with rotational linkages and facilitate the creation of homochiral extended porous structures that feature a helical arrangement of porphyrins. Post-synthetic metalation of CCOF 23 with Rh(I) affords a heterogeneous catalyst for the asymmetric Michael addition reaction of aryl boronic acids to 2-cyclohexenone, which shows higher enantioselectivities compared to their homogeneous counterparts, presumably due to the confined effect of helical channels. This finding will provide an impetus to explore multichirality materials, offering new insights into the generation and control of helicity, homochirality, and enantioselectivity in the solid state.

Electrochemical CO 2 reduction reaction (CO 2 RR) in acid can solve alkalinity issues while highly corrosive and reductive acidic electrolytes usually cause catalyst degradation. Inhibiting catalyst degradation is crucial for the stability of acidic CO 2 RR. Here, we reveal the microenvironment changes of dynamic Bi-based catalysts and develop a pulse chronoamperometry (CA) strategy to improve the stability of acidic CO 2 RR. In situ fluorescence mappings show that the local pH changes from neutral to acid, and the in situ Raman spectra reveal the dynamic evolution of interfacial water structures in the microenvironment. We propose that the surface charge properties of dynamic catalysts affect the competitive adsorption of K + and protons, thereby causing the differences in local pH and CO 2 RR intermediate adsorption. We also develop a pulse CA strategy to reactivate catalysts, and the stability of acidic CO 2 RR is improved by 2 orders of magnitude for 100 h operation, which is higher than most reports on the stability of acidic CO 2 RR. This work gives insights on how microenvironment changes affecting the stability of acidic CO 2 RR, and provides guidance for designing stable catalysts in acidic electrolytes.

Covalent organic frameworks (COFs) have undergone extensive research as heterogeneous catalysts for a wide range of significant reactions, but they have not yet been investigated in the realm of electrochemical asymmetric catalysis, despite their recognition as an economical and sustainable strategy for producing enantiopure compounds. Here, we report a mixed-linker strategy to design multicomponent two-dimensional (2D) chiral COFs with tunable layer stacking for highly enantioselective electrocatalysis. By crystallizing mixtures of triamines with and without the MacMillan imidazolidinone catalyst or aryl substituent (ethyl and isopropyl) and a dialdehyde derivative of thieno-[3,2- b ]thiophene, we synthesized and structurally characterized a series of three-component homochiral 2D COFs featuring either AA or ABC stacking. The stacking modes that can be synthetically controlled through steric tuning using different aryl substituents affect their chemical stability and electrochemical performance. With the MacMillan catalyst periodically appended on their channels, all three COFs with conductive thiophene moieties can be highly enantioselective and recyclable electrocatalysts for the asymmetric α-arylation of aldehydes, affording alkylated anilines with up to 97% enantiomeric excess by an anodic oxidation/organocatalytic protocol. Presumably due to their higher charge transfer ability, the ABC stacking COFs exhibit improved reactivity compared to the AA stacking analogue. This work therefore advances COFs as electrocatalysts for asymmetric catalysis and may facilitate the design of more redox-active crystalline organic polymers for electrochemical enantioselective processes.

Selective oxidation of benzylic C-H to benzylic alcohols is a well-known challenge in the chemical community since benzylic C-H is more prone to be overoxidized to benzylic ketones. In this work, we report the highly selective electro-oxidation of benzylic C-H to benzylic alcohols in an undivided cell in ionic liquid-based solution. As an example, the selectivity toward xanthydrol could be as high as 95.7% at complete conversion of xanthene, a typical benzylic C-H compound, on gram-scale in imidazolium bromide/H 2 O/DMF. Mechanism investigation reveals that the imidazolium radical generated in situ participants in a proton-coupled electron transfer process and low-barrier hydrogen bonds stabilize the reaction intermediates, together steering the redox equilibrium, favoring benzylic alcohols over benzylic ketones.

Rational regulation of the reaction pathway to produce the desired products is one of the most significant challenges in the electrochemical CO 2 reduction reaction (CO 2 RR). Herein, we designed a series of rare-earth Cu catalysts with mixed phases. It was found that the products could be switched from C 2+ to CH 4 by tuning the composition and structure of the catalysts. Particularly at the Cu/Sm atomic ratio of 9/1 (Cu 9 Sm 1 -O x ), the Faradaic efficiency (FE) for C 2+ products (FE C 2+ ) could reach 81% at 700 mA cm -2 with negligible CH 4 . However, the FE of CH 4 (FE CH 4 ) was 65% at 500 mA cm -2 over Cu 1 Sm 9 -O x (Cu/Sm = 1/9), and the FE C 2+ was extremely low. Experiments and theoretical studies indicated that the stable CuSm 2 O 4 phase existed in all the catalysts within the Cu/Sm range of 9/1 to 1/9. At a high Cu content, the catalyst was composed of CuSm 2 O 4 and Cu phases. The small amount of Sm could enhance the binding strength of *CO and facilitate C-C coupling. Conversely, at a high Sm content, the catalyst was composed of CuSm 2 O 4 and Sm 2 O 3 phases. Sm could effectively stabilize bivalent Cu and enrich proton donors, lowering the reaction energy of *CO for deep hydrogenation to generate CH 4 . In both pathways, the stable CuSm 2 O 4 phase could cooperate with the Cu or Sm 2 O 3 phases, which induced the formation of different microenvironments to generate different products. This strategy also had commonality with other Cu-rare-earth (La, Pr, and Eu) catalysts to boost the CO 2 RR for C 2+ or CH 4 production.

Cu-based electrocatalysts have great potential for facilitating CO 2 reduction to produce energy-intensive fuels and chemicals. However, it remains challenging to obtain high product selectivity due to the inevitable strong competition among various pathways. Here, we propose a strategy to regulate the adsorption of oxygen-associated active species on Cu by introducing an oxophilic metal, which can effectively improve the selectivity of C 2+ alcohols. Theoretical calculations manifested that doping of Lewis acid metal Al into Cu can affect the C-O bond and Cu-C bond breaking toward the selectively determining intermediate (shared by ethanol and ethylene), thus prioritizing the ethanol pathway. Experimentally, the Al-doped Cu catalyst exhibited an outstanding C 2+ Faradaic efficiency (FE) of 84.5% with remarkable stability. In particular, the C 2+ alcohol FE could reach 55.2% with a partial current density of 354.2 mA cm -2 and a formation rate of 1066.8 μmol cm -2 h -1 . A detailed experimental study revealed that Al doping improved the adsorption strength of active oxygen species on the Cu surface and stabilized the key intermediate *OC 2 H 5 , leading to high selectivity toward ethanol. Further investigation showed that this strategy could also be extended to other Lewis acid metals.

Metal nanoclusters have served as an emerging class of modular nanomaterials. Several efficient strategies have been proposed for transforming cluster precursors into new nanoclusters with customized structures and enhanced performance. However, such nanocluster transformations have still been in a "blind box" state, meaning that the existing intermediates were hard to track with atomic precision. Herein, we present a "slice visualization" approach for in-depth imaging of the nanocluster transformation from Au 1 Ag 24 (SR) 18 to Au 1 Ag 30 (SR) 20 . With this approach, two cluster intermediates, namely, Au 1 Ag 26 (SR) 19 and Au 1 Ag 28 (SR) 20 , were monitored with atomic precision. The four nanoclusters constituted a correlated Au 1 Ag 24+2 n ( n = 0, 1, 2, and 3) cluster series with comparable structural features─the same Au 1 Ag 12 icosahedral kernel but evolutionary peripheral motif structures. The mechanism of nanocluster structure growth was mapped in detail─insertion of Ag 2 (SR) 1 or Ag-induced assembly of surface subunits. The presented "slice visualization" approach not only contributes an ideal cluster platform for in-depth investigations of structure-property correlations but also hopefully acts as a powerful means for obtaining clear information on nanocluster structure evolution.

Using bulk metals as catalysts to get high efficiency in electro-reduction of CO 2 is ideal but challenging. Here, we report the coupling of bulk metal electrodes and a ternary ionic-liquid-based electrolyte, 1-butyl-3-methylimidazolium tetrafluoroborate/1-dodecyl-3-methylimidazolium tetrafluoroborate/MeCN to realize highly efficient electro-reduction of CO 2 to CO. Over various bulk metal electrodes, the ternary electrolyte not only increases the current density but also suppresses the hydrogen evolution reaction to obtain a high Faradaic efficiency (FE) toward CO. FE CO could maintain ∼100% over a wide potential range, and metal electrodes showed very high stability in the ternary electrolyte. It is demonstrated that the aggregation behavior of the ternary electrolyte and the arrangement of two kinds of IL cations with different chain lengths in the electrochemical double layer not only increase the wettability to electrode and CO 2 adsorption but also extend the diffusion channel of H + , rendering the high current density and FE CO .

Cu is a promising electrocatalyst in CO 2 reduction reaction (CO 2 RR) to high-value C 2+ products. However, as important C-C coupling active sites, the Cu + species is usually unstable under reduction conditions. How atomic dopants affect the performance of Cu-based catalysts is interesting to be studied. Herein, we first calculated the difference between the thermodynamic limiting potentials of CO 2 RR and the hydrogen evolution reaction, as well as the *CO binding energy over Cu 2 O doped with different metals, and the results indicated that doping atomic Gd into Cu 2 O could improve the performance of the catalyst effectively. On the basis of the theoretical study, we designed Gd 1 /CuO x catalysts. The distinctive electronic structure and large ion radii of Gd not only keep the Cu + species stable during the reaction but also induce tensile strain in Gd 1 /CuO x , resulting in excellent performance of the catalysts for electroreduction of CO 2 to C 2+ products. The Faradic efficiency of C 2+ products could reach 81.4% with a C 2+ product partial current density of 444.3 mA cm -2 at -0.8 V vs a reversible hydrogen electrode. Detailed experimental and theoretical studies revealed that Gd doping enhanced CO 2 activation on the catalyst, stabilized the key intermediate O*CCO, and reduced the energy barrier of the C-C coupling reaction.

Large-current electrolysis of CO 2 to multi-carbon (C 2+ ) products is critical to realize the industrial application of CO 2 conversion. However, the poor binding strength of *CO intermediates on the catalyst surface induces multiple competing pathways, which hinder the C 2+ production. Herein, we report that p-d orbital hybridization induced by Ga-doped Cu (CuGa) could promote efficient CO 2 electrocatalysis to C 2+ products at ampere-level current density. It was found that CuGa exhibited the highest C 2+ productivity with a remarkable Faradaic efficiency (FE) of 81.5% at a current density of 0.9 A/cm 2 , and the potential at such a high current density was -1.07 V versus reversible hydrogen electrode. At 1.1 A/cm 2 , the catalyst still maintained a high C 2+ productivity with an FE of 76.9%. Experimental and theoretical studies indicated that the excellent performance of CuGa results from the p-d hybridization of Cu and Ga, which not only enriches reactive sites but also enhances the binding strength of the *CO intermediate and facilitates C-C coupling. The p-d hybridization strategy can be extended to other p-block metal-doped Cu catalysts, such as CuAl and CuGe, to boost CO 2 electroreduction for C 2+ production. As far as we know, this is the first work to promote electrochemical CO 2 reduction reaction to generate the C 2+ product by p-d orbital hybridization interaction using a p-block metal-doped Cu catalyst.

The construction of helical nanosized superstructures has long been a challenging pursuit, and little has been achieved in terms of atomic-level manipulation. Herein, intercluster hierarchical triple-helical structures were presented from all-thiol-stabilized Au 6 Cu 6 (4-MeOBT) 12 nanoclusters by investigating their structures from both molecular and supramolecular aspects. Based on the atomically precise structure, the mechanism of intercluster assembly was elucidated, and the results indicated an intracluster rotation-induced self-assembly process. Specifically, the presence of abundant intermolecular interactions, including π-π stacking, C-H···O hydrogen bonding, and C-H···π interactions, was found to be beneficial for the organization of the triple-helical superstructure of metal clusters. Moreover, DFT calculations and UV-vis, Raman, and transient absorption measurements were performed to observe the different electronic structures between the nanocluster monomers and helical aggregates. Overall, this work presents an exciting example of the hierarchical triple-helical assembly of atomically precise nanoclusters, which allows an in-depth understanding of complex helical structures/behaviors at the atomic level.

The interactions between SbF 6 - and metal nanoclusters are of significance for customizing clusters from both structure and property aspects; however, the whole-segment monitoring of this customization remains challenging. In this work, by controlling the amount of introduced SbF 6 - anions, the step-by-step nanocluster evolutions from [Pt 1 Ag 28 (S-Adm) 18 (PPh 3 ) 4 ]Cl 2 (Pt 1 Ag 28 -Cl) to [Pt 1 Ag 28 (S-Adm) 18 (PPh 3 ) 4 ](SbF 6 ) 2 (Pt 1 Ag 28 -SbF 6 ) and then to [Pt 1 Ag 30 Cl 1 (S-Adm) 18 (PPh 3 ) 3 ](SbF 6 ) 3 (Pt 1 ) have been mapped out with X-ray crystallography, with which atomic-level SbF 30 -SbF 6 ) have been mapped out with X-ray crystallography, with which atomic-level SbF 6 - counterion effects in reconstructing and rearranging nanoclusters are determined. The structure-dependent optical properties, including optical absorption, photoluminescence, and electrochemiluminescence (ECL), of these nanoclusters are then explored. Notably, the Pt 1 Ag 30 -SbF 6 nanocluster was ultrabright with a high phosphorescence quantum yield of 85% in N 2 -purged solutions, while Pt 1 Ag 28 nanoclusters were fluorescent with weaker emission intensities. Furthermore, Pt 1 Ag 30 -SbF 6 displayed superior ECL efficiency over Pt 1 Ag 28 -SbF 6 , which was rationalized by its increased effectively exposed reactive facets. Both Pt 1 Ag 30 -SbF 6 and Pt 1 Ag 28 -SbF 6 demonstrated unprecedented high absolute ECL quantum efficiencies at sub-micromolar concentrations. This work is of great significance for revealing the SbF 6 - counterion effects on the control of both structures and luminescent properties.

Non-copper electrocatalysts are seldom reported to generate C 2+ products, and the efficiency over these catalysts is low. In this work, we report a nitrogen-doped γ-Fe 2 O 3 ( x Fe 2 O 3 -N@CN) electrocatalyst, which yield C 2 H 6 as the major product in an H-cell. At -2.0 V vs Ag/Ag + , the Faradaic efficiency (FE) for ethane reaches 42% with a current density of 32 mA cm -2 . This is the first report about selective CO 2 reduction to ethane (C 2 H 6 ) over an iron-based catalyst. The results showed that the catalyst possessing FeO 1.5- n N n sites enriched with oxygen vacancies was beneficial for the stabilization of *COOH intermediates. The exposure of two adjacent surfaces of Fe atoms was conducive to lowering the energy barrier for C-C coupling over FeO 1.5- n N n sites, facilitating the generation of C 2 H 6 . This work provides a strategy for the design of a novel iron-based catalyst with tunable local coordination and electronic structures for converting CO 2 into C 2 products in the CO 2 RR.

The carbon-carbon (C-C) bond formation is essential for the electroconversion of CO 2 into high-energy-density C 2+ products, and the precise coupling pathways remain controversial. Although recent computational investigations have proposed that the OC-COH coupling pathway is more favorable in specific reaction conditions than the well-known CO dimerization pathway, the experimental evidence is still lacking, partly due to the separated catalyst design and mechanistic/spectroscopic exploration. Here, we employ density functional theory calculations to show that on low-coordinated copper sites, the *CO bindings are strengthened, and the adsorbed *CO coupling with their hydrogenation species, *COH, receives precedence over CO dimerization. Experimentally, we construct a fragmented Cu catalyst with abundant low-coordinated sites, exhibiting a 77.8% Faradaic efficiency for C 2+ products at 300 mA cm -2 . With a suite of in situ spectroscopic studies, we capture an *OCCOH intermediate on the fragmented Cu surfaces, providing direct evidence to support the OC-COH coupling pathway. The mechanistic insights of this research elucidate how to design materials in favor of OC-COH coupling toward efficient C 2+ production from CO 2 reduction.

A large number of covalent organic frameworks (COFs) with two-dimensional (2D) layered structures have been reported, but their network structures are restricted to only seven topologies (namely, hcb , hxl , kgm , sql , tth , bex , and kgd ) because of the limited choice of building blocks. In this work, we illustrate how linking pseudo-fivefold symmetric 1,2,3,4,5-penta(4-formylphenyl)pyrrole with linear aromatic diamines through dynamic imine bonds produces three 2D porous COFs with an unprecedented cem topology, which represent the first examples of five-vertex semiregular Archimedean tessellations in COFs. The three 2D COFs are isostructural, and each adopts an eclipsed stacking structure with unidirectional hierarchical pores, in which the pyrrole unit is utilized as the five-vertex of network to form both square and triangular pores in a 3 3 .4 2 sequence. With high thermal and chemical resistances, the COF-packed HPLC columns show excellent performance to provide separation of 10 different polycyclic aromatic hydrocarbons, a group of the most widespread organic environmental pollutants. The implementation of five-vertex Archimedean tessellations thus couriers a strategy to design COFs with new topologies and paves a new way to expand the inimitable properties of COF materials.

Accomplishing optical activity in achiral materials has long been a challenge. Achiral nanomaterials that crystallize in achiral point groups are generally optically inactive. Herein we report the surprising observation of optical activity in several achiral point groups for supercrystals assembled from anisotropic metal nanoclusters with atomic precision. By analyzing multiple achiral nanoclusters with different molecular structures and symmetry space groups, we have identified that the molecular anisotropy of nanocluster entities and their asymmetric arrangement in point groups of supercrystals are the two key factors for the realization of optical activity in such supercrystals. We have further exploited the polarization effect of the nanocluster supercrystals as a polarization switch that can alter the polarized state of the linearly polarized light. Our findings have broadened the fundamental principles for producing nanomaterial-based optical activity and devices with polarization effects.

The inorganic-organic interface between metal catalysts and their substrates greatly influences reaction processes, but few studies of this interface have been conducted for a detailed understanding of its structure. Herein, we describe the synthesis and structural determination of an arylthiolated Au 25 (F-Ph) 18 - nanocluster and characterize in detail the key roles of its ligands in photocatalyzed oxidative functionalization reactions. The most significant findings are that (i) interactions are established between ligands to avoid distortion of the geometric structure, limit the Jahn-Teller effect, and protect the nanocluster from oxidization and (ii) the low energy gap (HOMO-LUMO) of the synthetic clusters enables three types of photocatalytic oxidative functionalization reactions by near-infrared light (850 nm).

The importance of selenium (Se) in biology and health has become increasingly clear. Hydrogen selenide (H 2 Se), the biologically available and active form of Se, is suggested to be an emerging nitric oxide (NO)-like signaling molecule . Nevertheless, the research on H 2 Se chemical biology has technique difficulties due to the lack of well-characterized and controllable H 2 Se donors under physiological conditions, as well as a robust assay for direct H 2 Se quantification. Motivated by these needs, here, we demonstrate that selenocyclopropenones and selenoamides are tunable donor motifs that release H 2 Se upon reaction with cysteine (Cys) at pH 7.4 and that structural modifications enable the rate of Cys-mediated H 2 Se release to be tuned. We monitored the reaction pathways for the H 2 Se release and confirmed H 2 Se generation qualitatively using different methods. We further developed a quantitative assay for direct H 2 Se trapping and quantitation in an aqueous solution, which should also be operative for investigating future H 2 Se donor motifs. In addition, we demonstrate that arylselenoamide has the capability of Cys-mediated H 2 Se release in cellular environments. Importantly, mechanistic investigations and density functional theory (DFT) calculations illustrate the plausible pathways of Cys-activated H 2 Se release from arylselenoamides in detail, which may help understand the mechanistic issues of the H 2 S release from pharmacologically important arylthioamides. We anticipate that the well-defined chemistries of Cys-activated H 2 Se donor motifs will be useful for studying Se biology and for development of new H 2 Se donors and bioconjugate techniques.

Oligonucleotide-based materials such as spherical nucleic acid (SNA) have been reported to exhibit improved penetration through the epidermis and the dermis of the skin upon topical application. Herein, we report a self-assembled, skin-depigmenting SNA structure, which is based upon a bifunctional oligonucleotide amphiphile containing an antisense oligonucleotide and a tyrosinase inhibitor prodrug. The two components work synergistically to increase oligonucleotide cellular uptake, enhance drug solubility, and promote skin penetration. The particles were shown to reduce melanin content in B16F10 melanoma cells and exhibited a potent antimelanogenic effect in an ultraviolet B-induced hyperpigmentation mouse model.

Efficient electro-reduction of CO 2 over metal-organic framework (MOF) materials is hindered by the poor contact between thermally synthesized MOF particles and the electrode surface, which leads to low Faradaic efficiency for a given product and poor electrochemical stability of the catalyst. We report a MOF-based electrode prepared via electro-synthesis of MFM-300(In) on an indium foil, and its activity for the electrochemical reduction of CO 2 is assessed. The resultant MFM-300(In)-e/In electrode shows a 1 order of magnitude improvement in conductivity compared with that for MFM-300(In)/carbon-paper electrodes. MFM-300(In)-e/In exhibits a current density of 46.1 mA cm -2 at an applied potential of -2.15 V vs Ag/Ag + for the electro-reduction of CO 2 in organic electrolyte, achieving an exceptional Faradaic efficiency of 99.1% for the formation of formic acid. The facile preparation of the MFM-300(In)-e/In electrode, coupled with its excellent electrochemical stability, provides a new pathway to develop efficient electro-catalysts for CO 2 reduction.

The metal-organic framework (MOF) HKUST-1 with a tbo topology serves as an archetypal tunable and isoreticular framework platform for targeting desired applications, but the design and synthesis of tbo -covalent organic frameworks (COFs) remains a formidable challenge. Here we demonstrate the successful use of reticular chemistry as an appropriate strategy for the design and deliberate construction of COFs with a tbo topology. The judicious selection of the perquisite planar building blocks, 4-connected square tetramine of porphyrin and 3-connected trigonal trialdehydes of triphenylamine, allows the condensation of two tbo -COFs, the first examples of COFs with a tbo topology. The resulting COFs both crystallize in the cubic Pm 3̅ space group and adopt a non-interpenetrated open framework, in which each tritopic linker connects to three square units forming a truncated T d -octahedron and occupies the alternating triangular faces of the truncated octahedron. Owing to the presence of two different types of photoredox-active moieties, the two COFs can be efficient heterogeneous photocatalysts for the oxidative hydroxylation of arylboronic acids and the reductive defluoroalkylation of trifluoromethyl aromatics with alkenes. The present finding will provide an impetus to examine the potential of tbo -COFs as a new platform for engineering multifunctional materials via expansion and functionalization of building blocks.

The design and development of robust and porous supported catalysts with high activity and selectivity is extremely significant but very challenging for eco-friendly synthesis of fine chemicals and pharmaceuticals. We report here the design and synthesis of highly stable chiral Zr(IV)-based MOFs with different topologies to support Ir complexes and demonstrate their network structures-dependent asymmetric catalytic performance. Guided by the modulated synthesis and isoreticular expansion strategy, five chiral Zr-MOFs with a flu or ith topology are constructed from enantiopure 1,1'-biphenol-derived tetracarboxylate linkers and Zr 6 , Zr 9 , or Zr 12 clusters. The obtained MOFs all show high chemical stability in boiling water, strongly acidic, and weakly basic aqueous solutions. The two flu MOFs featuring the dihydroxyl groups of biphenol in open and large cages, after sequential postsynthetic modification with P(NMe 2 ) 3 and [Ir(COD)Cl] 2 , can be highly efficient and recyclable heterogeneous catalysts for hydrogenation of α-dehydroamino acid esters with up to 98% ee, whereas the three ith MOFs featuring the dihydroxyl groups in small cages cannot be installed with P(NMe 2 ) 3 to support the Ir complex. Incorporation of Ir-phosphorus catalysts into Zr-MOFs leads to great enhancement of their chemical stability, durability, and even stereoselectivity. This work therefore not only advances Zr-MOFs as stable supports for labile metal catalysts for heterogeneous asymmetric catalysis but also provides a new insight into how highly active chiral centers can result due to the framework topology.

Photoinduced charge transfer across the metal oxide-organic ligand interface plays a key role in the diverse applications of metal oxide nanomaterials/nanostructures, such as photovoltaics, photocatalysis, and optoelectronics. Thus far, most studies are focused on molecular engineering of the organic chromophores, where the charge-transfer properties have been found to dictate the photo absorption efficiency and eventual device performance. Yet, as the chromophores are mostly bound onto the metal oxide surfaces by hydroxyl or carboxyl anchors, the impacts of the bonding interactions at the metal oxide-ligand interface on interfacial charge transfer have remained largely unexplored. Herein, acetylene derivatives are demonstrated as effective surface capping ligands for metal oxide nanoparticles, as exemplified with TiO 2 , RuO 2 , and ZnO. Experimental studies and first-principles calculations suggest the formation of M-O-C≡C- core-ligand linkages that lead to effective interfacial charge delocalization, in contrast to hopping/tunneling by the conventional M-O-CO- interfacial bonds in the carboxyl-capped counterparts. This leads to the generation of an interfacial state within the oxide bandgap and much enhanced sensitization of the nanoparticle photoluminescence emissions as well as photocatalytic activity, as manifested in the comparative studies with TiO 2 nanoparticles functionalized with ethynylpyrene and pyrenecarboxylic acid. These results highlight the significance of the unique interfacial bonding chemistry by acetylene anchoring group in facilitating efficient charge transfer through the oxide-ligand interfacial linkage and hence the fundamental implication in their practical applications.

RNAi approaches have been widely combined with platinum-based anticancer agents to elucidate cellular responses and to target gene products that mediate acquired resistance. Recent work has demonstrated that platination of siRNA prior to transfection may negatively influence RNAi efficiency based on the position and sequence of its guanosine nucleosides. Here, we used detailed spectroscopic characterization to demonstrate rapid formation of Pt-guanosine adducts within 30 min after coincubation of oxaliplatin [OxaPt(II)] or cisplatin [CisPt(II)] with either guanosine monophosphate or B-cell lymphoma 2 (BCL-2) siRNA. After 3 h of exposure to these platinum(II) agents, >50% of BCL-2 siRNA transcripts were platinated and unable to effectively suppress mRNA levels. Platinum(IV) analogues [OxaPt(IV) or CisPt(IV)] did not form Pt-siRNA adducts but did display decreased in vitro uptake and reduced potency. To overcome these challenges, we utilized biodegradable methoxyl-poly(ethylene glycol)-block-poly(ε-caprolactone)-block-poly(l-lysine) (mPEG-b-PCL-b-PLL) to generate self-assembled micelles that covalently conjugated OxaPt(IV) and/or electrostatically complexed siRNA. We then compared multiple strategies by which to combine BCL-2 siRNA with either OxaPt(II) or OxaPt(IV). Overall, we determined that the concentrations of siRNA (nM) and platinum(II)-based anticancer agents (μM) that are typically used for in vitro experiments led to rapid Pt-siRNA adduct formation and ineffective RNAi. Coincorporation of BCL-2 siRNA and platinum(IV) analogues in a single micelle enabled maximal suppression of BCL-2 mRNA levels (to <10% of baseline), augmented the intracellular levels of platinum (by ∼4×) and the numbers of resultant Pt-DNA adducts (by >5×), increased the cellular fractions that underwent apoptosis (by ∼4×), and enhanced the in vitro antiproliferative activity of the corresponding platinum(II) agent (by 10-100×, depending on the cancer cell line). When combining RNAi and platinum-based anticancer agents, this generalizable strategy may be adopted to maximize synergy during screening or for therapeutic delivery.

Carbon-carbon bond cleavage of benzene by transition metals is of great fundamental interest and practical importance, as this transformation is involved in the production of fuels and other important chemicals in the industrial hydrocracking of naphtha on solid catalysts. Although this transformation is thought to rely on cooperation of multiple metal sites, molecular-level information on the reaction mechanism has remained scarce to date. Here, we report the DFT studies of the ring cleavage and contraction of benzene by a molecular trinuclear titanium hydride cluster. Our studies suggest that the reaction is initiated by benzene coordination, followed by H2 release, C6H6 hydrometalation, repeated C-C and C-H bond cleavage and formation to give a MeC5H4 unit, and insertion of a Ti atom into the MeC5H4 unit with release of H2 to give a metallacycle product. The C-C bond cleavage and ring contraction of toluene can also occur in a similar fashion, though some details are different due to the presence of the methyl substituent. Obviously, the facile release of H2 from the metal hydride cluster to provide electrons and to alter the charge population at the metal centers, in combination with the flexible metal-hydride connections and dynamic redox behavior of the trimetallic framework, has enabled this unusual transformation to occur. This work has not only provided unprecedented insights into the activation and transformation of benzene over a multimetallic framework but it may also offer help in the design of new molecular catalysts for the activation and transformation of inactive aromatics.

This study presents a new crystal structure of a gold nanocluster coprotected by thiolate and chloride, with the formula of Au36(SCH2Ph-(t)Bu)8Cl20. This nanocluster is composed of a Au14 core with two Cl atoms, a pair of pentameric Au5(SCl5) staple motifs, and a pair of hexameric Au6(S3Cl4) motifs. It is noteworthy that the "Au-Cl-Au" staple motifs are observed for the first time in thiolate protected gold nanoclusters. More importantly, the formation of the Cl-Au3 motifs is found to be mainly responsible for the configuration of the gold nanocluster. This work will offer a new perspective to understand how the ligands affect the crystal structure of gold nanocluster.

Stable porous ionic liquid-water gel induced by inorganic salts was created for the first time. The porous gel was used to develop a one-step method to synthesize supported metal nanocatalysts. Au/SiO2, Ru/SiO2, Pd/Cu(2-pymo)2 metal-organic framework (Cu-MOF), and Au/polyacrylamide (PAM) were synthesized, in which the supports had hierarchical meso- and macropores, the size of the metal nanocatalysts could be very small (<1 nm), and the size distribution was very narrow even when the metal loading amount was as high as 8 wt %. The catalysts were extremely active, selective, and stable for oxidative esterification of benzyl alcohol to methyl benzoate, benzene hydrogenation to cyclohexane, and oxidation of benzyl alcohol to benzaldehyde because they combined the advantages of the nanocatalysts of small size and hierarchical porosity of the supports. In addition, this method is very simple.

We report the X-ray structure of a selenolate-capped Au24(SeR)20 nanocluster (R = C6H5). It exhibits a prolate Au8 kernel, which can be viewed as two tetrahedral Au4 units cross-joined together without sharing any Au atoms. The kernel is protected by two trimeric Au3(SeR)4 staple-like motifs as well as two pentameric Au5(SeR)6 staple motifs. Compared to the reported gold-thiolate nanocluster structures, the features of the Au8 kernel and pentameric Au5(SeR)6 staple motif are unprecedented and provide a structural basis for understanding the gold-selenolate nanoclusters.

Stable ruthenium nanoparticles were prepared by the self-assembly of 1-dodecyne onto the "bare" Ru colloid surface. The formation of a Ru-vinylidene (Ru═C═CH-R) interfacial bonding linkage was confirmed by the specific reactivity of the nanoparticles with imine derivatives to form a heterocyclic complex at the metal-ligand interface, as manifested in (1)H and (13)C NMR, photoluminescence, and electrochemical measurements in which a ferrocenyl imine was used as the labeling probe. Notably, the resulting nanoparticles could also undergo olefin metathesis reactions with vinyl-terminated molecules, as exemplified by the functionalization of the nanoparticles with 1-vinylpyrene. In sharp contrast, no reactvity was observed with 1-dodecynide-stabilized ruthenium nanoparticles with either imine or vinyl derivatives, indicating that these (deprotonated) nanoparticles were stabilized instead by the formation of a Ru-C≡ dπ bond at the metal-ligand interface., (© 2012 American Chemical Society)

Using low-pressure carbon dioxide (CO2), we demonstrated a novel and versatile approach to assembling polymeric constructs in the presence of cells and/or biomolecules in an aqueous environment. By regulating the CO2 pressure, the assembly was completed at biologically permissive temperatures with excellent preservation of the original structures. We further demonstrated that mammalian cells can survive the CO2-assisted bioassembly process (37 degrees C, 1.38 MPa, approximately 1 h). Human mesenchymal stem cells from bone marrow (hMSCs) exhibited the same cell morphology and proliferation potential as the untreated control. Mouse embryonic stem cells (mESCs) maintained ES-specific Oct-4 gene expression and differentiation potential after CO2 treatment as well. This method highlights the ability to construct multiple biodegradable polymeric scaffolds with well-defined architecture, on which various types of cells were grown, into a predesigned three-dimensional complex. In addition, protein and DNA bioactivity can be preserved in the context of a CO2-assisted assembly. This CO2-assisted bioassembly method provides for a manufacturing platform that, thus far, has been lacking in the fields of tissue engineering, cell-based biochips, cell therapy, and drug delivery.