Electrocatalytic Nitrate Reduction on Metallic CoNi-Terminated Catalyst with Industrial-Level Current Density in Neutral Medium

Green ammonia synthesis through electrocatalytic nitrate reduction reaction (eNO3RR) can serve as an effective alternative to the traditional energy-intensive Haber-Bosch process. However, achieving high Faradaic efficiency (FE) at industrially relevant current density in neutral medium poses significant challenges in eNO3RR. Herein, with the guidance of theoretical calculation, a metallic CoNi-terminated catalyst is successfully designed and constructed on copper foam, which achieves an ammonia FE of up to 100% under industrial-level current density and very low overpotential (-0.15 V versus reversible hydrogen electrode) in a neutral medium. Multiple characterization results have confirmed that the maintained metal atom-terminated surface through interaction with copper atoms plays a crucial role in reducing overpotential and achieving high current density. By constructing a homemade gas stripping and absorption device, the complete conversion process for high-purity ammonium nitrate products is demonstrated, displaying the potential for practical application. This work suggests a sustainable and promising process toward directly converting nitrate-containing pollutant solutions into practical nitrogen fertilizers.

Introducing Carborane Clusters into Crystalline Frameworks via Thiol-Yne Click Chemistry for Energetic Materials

Crystalline frameworks represent a cutting-edge frontier in material science, and recently, there has been a surge of interest in energetic crystalline frameworks. However, the well-established porosity often leads to diminished output energy, necessitating a novel approach for performance enhancement. Thiol-yne coupling, a versatile metal-free click reaction, has been underutilized in crystalline frameworks. As a proof of concept, we herein demonstrate the potential of this approach by introducing the energy-rich, size-matched, and reductive 1,2-dicarbadodecaborane-1-thiol (CB-SH) into an acetylene-functionalized framework, Zn(AIm)2, via thiol-yne click reaction. This innovative decoration strategy resulted in a remarkable 46.6 % increase in energy density, a six-fold reduction in ignition delay time (4 ms) with red fuming nitric acid as the oxidizer, and impressive enhancement of stability. Density functional theory calculations were employed to elucidate the mechanism by which CB-SH promotes hypergolic ignition. The thiol-yne click modification strategy presented here permits engineering of crystalline frameworks for the design of advanced energetic materials.

Stepwise structural evolution toward robust carboranealkynyl-protected copper nanocluster catalysts for nitrate electroreduction

Atomically precise metal nanoclusters (NCs) are emerging as idealized model catalysts for imprecise metal nanoparticles to unveil their structure-activity relationship. However, the directional synthesis of robust metal NCs with accessible catalytic active sites remains a great challenge. In this work, we achieved bulky carboranealkynyl-protected copper NCs, the monomer Cu13·3PF6 and nido-carboranealkynyl bridged dimer Cu26·4PF6, with fair stability as well as accessible open metal sites step by step through external ligand shell modification and metal-core evolution. Both Cu13·3PF6 and Cu26·4PF6 demonstrate remarkable catalytic activity and selectivity in electrocatalytic nitrate (NO3-) reduction to NH3 reaction, with the dimer Cu26·4PF6 displaying superior performance. The mechanism of this catalytic reaction was elucidated through theoretical computations in conjunction with in situ FTIR spectra. This study not only provides strategies for accessing desired copper NC catalysts but also establishes a platform to uncover the structure-activity relationship of copper NCs.

Chemical Flexibility of Atomically Precise Metal Clusters

Ligand-protected metal clusters possess hybrid properties that seamlessly combine an inorganic core with an organic ligand shell, imparting them exceptional chemical flexibility and unlocking remarkable application potential in diverse fields. Leveraging chemical flexibility to expand the library of available materials and stimulate the development of new functionalities is becoming an increasingly pressing requirement. This Review focuses on the origin of chemical flexibility from the structural analysis, including intra-cluster bonding, inter-cluster interactions, cluster-environments interactions, metal-to-ligand ratios, and thermodynamic effects. In the introduction, we briefly outline the development of metal clusters and explain the differences and commonalities of M(I)/M(I/0) coinage metal clusters. Additionally, we distinguish the bonding characteristics of metal atoms in the inorganic core, which give rise to their distinct chemical flexibility. Section 2 delves into the structural analysis, bonding categories, and thermodynamic theories related to metal clusters. In the following sections 3 to 7, we primarily elucidate the mechanisms that trigger chemical flexibility, the dynamic processes in transformation, the resultant alterations in structure, and the ensuing modifications in physical-chemical properties. Section 8 presents the notable applications that have emerged from utilizing metal clusters and their assemblies. Finally, in section 9, we discuss future challenges and opportunities within this area.

Vibration-Dependent Dual-Phosphorescent Cu4 Nanocluster with Remarkable Piezochromic Behavior

The dual emission (DE) characteristics of atomically precise copper nanoclusters (Cu NCs) are of significant theoretical and practical interest. Despite this, the underlying mechanism driving DE in Cu NCs remains elusive, primarily due to the complexities of excited state processes. Herein, a novel [Cu4(PPh3)4(C≡C-p-NH2C6H4)3]PF6 (Cu4) NC, shielded by alkynyl and exhibiting DE, was synthesized. Hydrostatic pressure was applied to Cu4, for the first time, to investigate the mechanism of DE. With increasing pressure, the higher-energy emission peak of Cu4 gradually disappeared, leaving the lower-energy emission peak as the dominant emission. Additionally, the Cu4 crystal exhibited notable piezochromism transitioning from cyan to orange. Angle-dispersive synchrotron X-ray diffraction results revealed that the reduced inter-cluster distances under pressure brought the peripheral ligands closer, leading to the formation of new C-H···N and N-H···N hydrogen bonds in Cu4. It is proposed that these strengthened hydrogen bond interactions limit the ligands´ vibration, resulting in the vanishing of the higher-energy peak. In situ high-pressure Raman and vibrationally resolved emission spectra demonstrated that the benzene ring C=C stretching vibration is the structural source of the DE in Cu4.

Viologen-based ionic conjugated mesoporous polymer as the electron conveyer for efficient polysulfide trapping and conversion

The commercialization of lithium-sulfur (Li-S) batteries has been hindered by the shuttle effect and sluggish redox kinetics of lithium polysulfides (LiPSs). Herein, we reported a viologen-based ionic conjugated mesoporous polymer (TpV-Cl), which acts as the cathode host for modifying Li-S batteries. The viologen component serves as a reversible electron conveyer, leading to a comprehensive enhancement in the adsorption of polysulfides and improved conversion rate of polysulfides during the electrochemical process. As a result, the S@TpV-PS cathode exhibits outstanding cycling performance, achieving 300 cycles at 2.0 C (1 C = 1675 mA g-1) with low decay rate of 0.032% per cycle. Even at a high sulfur loading of 4.0 mg cm-2, S@TpV-PS shows excellent cycling stability with a Coulombic efficiency of up to 98%. These results highlight the significant potential of S@TpV-PS in developing high-performance Li-S batteries.

Construction of novel Ag(0)-containing silver nanoclusters by regulating auxiliary phosphine ligands

Controlled synthesis of metal clusters through minor changes in surface ligands holds significant interest because the corresponding entities serve as ideal models for investigating the ligand environment's stereochemical and electronic contributions that impact the corresponding structures and properties of metal clusters. In this work, we obtained two Ag(0)-containing nanoclusters (Ag17 and Ag32) with near-infrared emissions by regulating phosphine auxiliary ligands. Ag17 and Ag32 bear similar shells wherein Ag17 features a trigonal bipyramid Ag5 kernel while Ag32 has a bi-icosahedral interpenetrating an Ag20 kernel. Ag17 and Ag32 showed a near-infrared emission (NIR) of around 830 nm. Benefiting from the rigid structure, Ag17 displayed a more intense near-infrared emission than Ag32. This work provides new insight into the construction of novel superatomic silver nanoclusters by regulating phosphine ligands.

Boosting 2000-Fold Hypergolic Ignition Rate of Carborane by Substitutes Migration in Metal Clusters

Hypergolic propellants rely on fuel and oxidizer that spontaneously ignite upon contact, which fulfill a wide variety of mission roles in launch vehicles and spacecraft. Energy-rich carboranes are promising hypergolic fuels, but triggering their energy release is quite difficult because of their ultrastable aromatic cage structure. To steer the development of carborane-based high-performance hypergolic material, carboranylthiolated compounds integrated with atomically precise copper clusters are presented, yielding two distinct isomers, Cu14B-S and Cu14C-S, both possessing similar ligands and core structures. With the migration of thiolate groups from carbon atoms to boron atoms, the ignition delay (ID) time shortened from 6870 to 3 ms when contacted with environmentally benign oxidizer high-test peroxide (HTP, with a H2O2 concentration of 90%). The extraordinarily short ignition ID time of Cu14B-S is ranking among the best of HTP-active hypergolic materials. The experimental and theoretical findings reveal that benefitting from the migration of thiolate groups, Cu14B-S, characterized by an electron-rich metal kernel, displays enhanced reducibility and superior charge transfer efficiency. This results in exceptional activation rates with HTP, consequently inducing carborane combustion and the simultaneous release of energy. This fundamental investigation shed light on the development of advanced green hypergolic propulsion systems.

Staggered Assembly of a Dimeric Au13 Cluster: Impacts on Coupling of Geometric Isomerism

The specific states of aggregation of metal atoms in sub-nanometer-sized gold clusters are related to the different quantum confinement volumes of electrons, leading to novel optical and electronic properties. These volumes can be tuned by changing the relative positions of the gold atoms to generate isomers. Studying the isomeric gold core and the electron coupling between the basic units is fundamentally important for nanoelectronic devices and luminescence; however, appropriate cases are lacking. In this study, the structure of the first staggered di-superatomic Au25 -S was solved using single-crystal X-ray diffraction. The optical properties of Au25 -S were studied by comparing with eclipsed Au25 -E. From Au25 -E to Au25 -S, changes in the electronic structures occurred, resulting in significantly different optical absorptions originating from the coupling between the two Au13 modules. Au25 -S shows a longer electron decay lifetime of 307.7 ps before populating the lowest triplet emissive state, compared to 1.29 ps for Au25 -E. The experimental and theoretical results show that variations in the geometric isomerism lead to distinct photophysical processes owing to isomerism-dependent electronic coupling. This study offers new insights into the connection between the geometric isomerism of nanosized building blocks and the optical properties of their assemblies, opening new possibilities for constructing function-specific nanomaterials.

Asymmetrical Interactions between Ni Single Atomic Sites and Ni Clusters in a 3D Porous Organic Framework for Enhanced CO2 Photoreduction

3D porous organic frameworks, which possess the advantages of high surface area and abundant exposed active sites, are considered ideal platforms to accommodate single atoms (SAs) and metal nanoclusters (NCs) in high-performance catalysts; however, very little research has been conducted in this field. In the present work, a 3D porous organic framework containing Ni1 SAs and Nin NCs is prepared through the metal-assisted one-pot polycondensation of tetraaldehyde and hexaaminotriptycene. The single metal sites and metal clusters confined in the 3D space created a favorable micro-environment that facilitated the activation of chemically inert CO2 molecules, thus promoting the overall photoconversion efficiency and selectivity of CO2 reduction. The 3D-NiSAs/NiNCs-POPs, as a CO2 photoreduction catalyst, demonstrated an exceptional CO production rate of 6.24 mmol g-1  h-1 , high selectivity of 98%, and excellent stability. The theoretical calculations uncovered that asymmetrical interaction between Ni1 SAs and Nin NCs not only favored the bending of CO2 molecules and reducing the CO2 reduction energy, but also regulated the electronic structure of the catalyst leading to the optimal binding strength of intermediates.

Microwave-Assisted Rapid Synthesis of MOF-Based Single-Atom Ni Catalyst for CO2 Electroreduction at Ampere-Level Current

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.

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.

Tandem Nitrate-to-Ammonia Conversion on Atomically Precise Silver Nanocluster/MXene Electrocatalyst

Electrocatalytic reduction of nitrate (NO3 RR) to synthesize ammonia (NH3 ) provides a competitive manner for carbon neutrality and decentralized NH3 synthesis. Atomically precise nanoclusters, as an advantageous platform for investigating the NO3 RR mechanisms and actual active sites, remain largely underexplored due to the poor stability. Herein, we report a (NH4 )9 [Ag9 (mba)9 ] nanoclusters (Ag9 NCs) loaded on Ti3 C2 MXene (Ag9 /MXene) for highly efficient NO3 RR performance towards ambient NH3 synthesis with improved stability in neutral medium. The composite structure of MXene and Ag9 NCs enables a tandem catalysis process for nitrate reduction, significantly increasing the selectivity and FE of NH3 . Besides, compared with individual Ag9 NCs, Ag9 /MXene has better stability with the current density performed no decay after 108 hours of reaction. This work provides a strategy for improving the catalytic activity and stability of atomically precise metal NCs, expanding the mechanism research and application of metal NCs.

Metal Clusters Confined in Chiral Zeolitic Imidazolate Framework for Circularly Polarized-Luminescence Inks

Chiroptical activities arising in nanoclusters (NCs) are emerging as one of the most dynamic areas of modern science. However, devising an overarching strategy that is capable of concurrently enhancing the photoluminescence (PL) and circularly polarized luminescence (CPL) of metal NCs remains a formidable challenge. Herein, gold and silver nanoclusters (AuNCs, AgNCs) are endowed with CPL, for the first time, through a universal host-guest approach─centered around perturbing a chiral microenvironment within chiral hosts, simultaneously enhancing emissions. Remarkably, the photoluminescence quantum yield (PLQY) of AuNCs has undergone an increase of over 200 times upon confinement, escalating from 0.05% to 12%, and demonstrates a CPL response. Moreover, a three-dimensional (3D) model termed "NCs@CMOF" featuring CPL activity is created using metal cluster-based assembly inks through the process of 3D printing. This work introduces a potentially straightforward and versatile approach for achieving both PL enhancement and CPL activities in metal clusters.

High-Efficiency Circularly Polarized Light-Emitting Diodes Based on Chiral Metal Nanoclusters

Circularly polarized light-emitting diodes (CP-LEDs) are critical for next-generation optical technologies, ranging from holography to quantum information processing. Currently deployed chiral luminescent materials, with their intricate synthesis and processing and limited efficiency, are the main bottleneck for CP-LEDs. Chiral metal nanoclusters (MNCs) are potential CP-LED materials, given their ease of synthesis and processability as well as diverse structures and excited states. However, their films are usually plagued by inferior electronic quality and aggregation-caused photoluminescence quenching, necessitating their incorporation into host materials; without such a scheme, MNC-based LEDs exhibit external quantum efficiencies (EQEs) < 10%. Herein, we achieve an efficiency leap for both CP-LEDs and cluster-based LEDs by using novel chiral MNCs with aggregation-induced emission enhancement. CP-LEDs using enantiopure MNC films attain EQEs of up to 23.5%. Furthermore, by incorporating host materials, the devices yield record EQEs of up to 36.5% for both CP-LEDs and cluster-based LEDs, along with electroluminescence dissymmetry factors (|gEL|) of around 1.0 × 10-3. These findings open a new avenue for advancing chiral light sources for next-generation optoelectronics.

Thiacalix[4]arene Etching of an Anisotropic Cu70H22 Intermediate for Accessing Robust Modularly Assembled Copper Nanoclusters

Atom-precise metal nanoclusters (NCs) with large bulk (nuclearity >60) are important species for insight into the embryonic phase of metal nanoparticles and their top-down etching synthesis. Herein, we report a metastable rod-shaped 70-nuclei copper-hydride NC, [Cl@Cu70H22(PhC≡C)29(CF3COO)16]2+ (Cu70), with Cl- as the template, in which the Cl@Cu59 kernel adopts a distinctive metal packing mode along the bipolar direction, and the protective ligand shell exhibits corresponding site differentiation. In terms of metal nuclearity, Cu70 is the largest alkynyl-stabilized Cu-hydride cluster to date. As a typical highly active intermediate, Cu70 could undergo a transformation into a series of robust modularly assembled Cu clusters (B-type Cu8, A-A-type Cu22, A-B-type Cu23, and A-B-A-type Cu38) upon etching by p-tert-butylthiacalix[4]arene (H4TC4A), which could not be achieved by "one-pot" synthetic methods. Notably, the patterns of A and B blocks in the Cu NCs could be effectively modulated by employing appropriate counterions and blockers, and the modular assembly mechanism was illustrated through comprehensive solution chemistry analysis using HR-ESI-MS. Furthermore, catalytic investigations reveal that Cu38 could serve as a highly efficient catalyst for the cycloaddition of propargylic amines with CO2 under mild conditions. This work not only enriched the family of high-nuclear copper-hydride NCs but also provided new insights into the growth mechanism of metal NCs.

Engineering High-Performance Hypergolic Propellant by Synergistic Contribution of Metal-Organic Framework Shell and Aluminum Core

Hypergolicity is a highly desired characteristic for hybrid rocket engine-based fuels because it eliminates the need for a separate ignition system. Introducing hypergolic additives into conventional fuels through physical mixing is a feasible approach, but achieving highly reliable hypergolic ignition and energy release remains a major challenge. Here, the construction of core-shell Al@metal organic framework (MOF) heterostructures is reported as high-performance solid hypergolic propellants. Upon contact with the liquid oxidizer the uniformly distributed hypergolic MOF (Ag-MOF) shell can induce the ignition of hypergolic-inert fuel Al, resulting in Al combustion. Such a synthetic strategy is demonstrated to be favorable in hotspot generation and heat transfer relative to a simple physical mixture of Al/Ag-MOF, thus producing shorter ignition delay times and more efficient combustion. Thermal reactivity study indicated that the functionalization of the Ag-MOF shell changes the energy release process of the inner Al, which is accompanied by a thermite reaction. The synergistic effect of implantation of hypergolic MOF and high energy Al contributes to high specific impulses of 230-270 s over a wide range of oxidizer-to-fuel ratios.

A Universal Electrochemical Synthetic Strategy for the Direct Assembly of Single-Atom Catalysts

Single-atom catalysts (SACs) have been one of the frontiers in the field of catalysis in recent years owing to their high atomic utilization and unique electronic structure. To facilitate the practical application of single-atom, it is vital to develop a sustainable, facile single-atom preparation method with mass production potential. Herein, a universal one-step electrochemical synthesis strategy is proposed, and various metal-organic framework-supported SACs (including Pt, Au, Ir, Pd, Ru, Mo, Rh, and W) are straightforwardly obtained by simply replacing the guest metal precursors. As a proof-of-concept, the electrosynthetic Pt-based catalysts exhibit outstanding activity and stability in the electrocatalytic hydrogen evolution reaction (HER). This study not only enriches the single-atom synthesis methodology, but also extends the scenario of electrochemical synthesis, opening up new avenues for the design of advanced electro-synthesized catalysts.

High-Efficiency Pure Blue Circularly Polarized Phosphorescence from Chiral N-Heterocyclic-Carbene-Stabilized Copper(I) Clusters

Circularly polarized luminescence (CPL) materials have attracted considerable attention for their promising applications in encryption, chiral sensing, and three-dimensional (3D) displays. However, the preparation of high-efficiency, pure blue CPL materials remains challenging. In this study, we reported an enantiomeric pair of triangle copper(I) clusters (R/S-Cu3) rigidified by employing chiral N-heterocyclic carbene (NHC) ligands with two pyridine-functionalized wingtips. These chiral clusters emitted pure blue phosphorescence that overlapped with that of the commercial blue phosphor having Commission Internationale de l'Eclairage (CIE) chromaticity coordinates of (0.14, 0.10), and the films exhibited an unprecedented photoluminescence quantum yield (PLQY) of ∼70.0%. Additionally, the solutions showed very bright circularly polarized phosphorescence (CPP) with a dissymmetry factor of ±2.1 × 10-3. The excellent solubility and photostability endowed these pure-blue-emitting chiral clusters with promising applications as pure blue CPP inks for 3D printing white objects, such as precise-atomic-enlarged models of metal clusters and a lovely white stereoscopic "rabbit". The intricate mechanism underlying blue phosphorescence in this small cluster and across various states is elucidated through a comprehensive approach that integrates thorough analysis of luminescence properties, controlled experiments, and theoretical calculations. For the first time, we propose that the dominant high-energy emission center is constituted by delocalized hybrid orbitals over multiple atomic centers, encompassing both the metal and the coordinated atoms. This challenges stereotypical assumptions that the cluster center solely supports low-energy emissions. This work expands the currently limited range of CPP functional materials and provides a new direction for CPP applications involving NHC-stabilized metal clusters.

Highly Efficient Stable Luminescent Radical-Based X-ray Scintillator

Stable luminescent radicals are open-shell emitters with unique doublet emission characteristics. This feature makes stable luminescent radicals exhibit widespread application prospects in constructing optical, electrical, and magnetic materials. In this work, a stable luminescent radical-based X-ray scintillator of AuPP-1.0 was prepared, which exhibited a high X-ray excited luminescence (XEL) efficiency as well as excellent stability. A mechanism study showed that the heavy atom of Au in AuPP-1.0 endowed it with effective absorption of X-rays, and the doublet emission characteristics of AuPP-1.0 significantly increased its exciton utilization rate in the radioluminescence process. Moreover, AuPP-1.0 has good processability to fabricate a flexible screen for high-quality X-ray imaging, whose resolution can reach 20 LP mm-1. This work demonstrates that the doublet emission is beneficial for improving the exciton utilization rate of radioluminescence, providing a brand-new strategy for the construction of high-performance X-ray scintillators.

Copper-Sulfur-Nitrogen Cluster Providing a Local Proton for Efficient Carbon Dioxide Photoreduction

Atomically precise Cu clusters are highly desirable as catalysts for CO2 reduction reaction (CO2 RR), and they provide an appropriate model platform for elaborating their structure-activity relationship. However, an efficient overall photocatalytic CO2 RR with H2 O using assembled Cu-cluster aggregates as single component photocatalyst has not been reported. Herein, we report a stable crystalline Cu-S-N cluster photocatalyst with local protonated N-H groups (denoted as Cu6 -NH). The catalyst exhibits suitable photocatalytic redox potentials, high structural stability, active catalytic species, and a narrow band gap, which account for its outstanding photocatalytic CO2 RR performance under visible light, with ≈100 % selectivity for CO evolution. Remarkably, systematic isostructural Cu-cluster control experiments, in situ infrared spectroscopy, and density functional theory calculations revealed that the protonated pyrimidine N atoms in the Cu6 -NH cluster act as a proton relay station, providing a local proton during the photocatalytic CO2 RR. This efficiently lowers the energy barrier for the formation of the *COOH intermediate, which is the rate-limiting step, efficiently enhancing the photocatalytic performance. This work lays the foundation for the development of atomically precise metal-cluster-based photocatalysts.

Halogen bonding-driven chiral amplification of a bimetallic gold-copper cluster through hierarchical assembly

Understanding the fundamentals and applications of chirality relies substantially on the amplification of chirality through hierarchical assemblies involving various weak interactions. However, a notable challenge remains for metal clusters chiral assembly driven by halogen bonding, despite their promising applications in lighting, catalysis, and biomedicine. Here, we used halogen bonding-driven assembly to achieve a hierarchical degree of achiral emissive Au2Cu2 clusters. From single crystals to one-dimensional ribbons and then to helixes, the morphologies were primarily modulated by intermolecular halogen bonding that evoked by achiral or/and chiral iodofluorobenzene (IFBs) molecules. Concomitantly, the luminescence and circularly polarized luminescence (CPL) changed a lot, ultimately leading to a substantial increase in the luminescence dissymmetry g-factor (glum) of 0.036 in the supramolecular helix. This work opens an avenue for hierarchical assemblies using predesigned metal clusters as building blocks though directional halogen bonding. This achievement marks a noteworthy advancement in the field of nanosized inorganic functional blocks.

Solvation-Mediated Self-Assembly from Crystals to Helices of Protic Acyclic Carbene AuI -Enantiomers with Chirality Amplification

Constructing chiral supramolecular assembly and exploring the underlying mechanism are of great significance in promoting the development of circularly polarized luminescence (CPL)-active materials. Herein, we report a solvation-mediated self-assembly from single-crystals to helical nanofibers based on the first protic acyclic (methoxy)(amino)carbenes (pAMACs) AuI -enantiomers driven by a synergetic aurophilic interactions and H-bonds. Their aggregation-dependent thermally activated delayed fluorescence properties with high quantum yields (ΦFL ) up to 95 % were proved to be attributed to packing modes of Au⋅⋅⋅Au dimers with π-stacking or one-dimensional extended Au⋅⋅⋅Au chains. Via drop-casting method, supramolecular P- or M-helices were prepared. Detailed studies on the helices demonstrate that formations of extended helical Au⋅⋅⋅Au molecular chains amplify supramolecular chirality, leading to strong CPL with high dissymmetry factor (|glum |=0.030, ΦFL =67 %) and high CPL brightness (BCPL ) of 4.87×10-3 . Our findings bring new insights into the fabrication of helical structures to improve CPL performance by modifying aurophilic interactions.

Neighboring Platinum Atomic Sites Activate Platinum-Cobalt Nanoclusters as High-Performance ORR/OER/HER Electrocatalysts

The rational design of efficient and multifunctional electrocatalysts for energy conversion devices is one of the major challenges for clean and renewable energy transition. Herein, the local electronic structure of cobalt-platinum nanoclusters is regulated by adjacent platinum atomic site encapsulated in N-doped hollow carbon nanotubes (PtSA -PtCo NCs/N-CNTs) by pyrolysis of melamine-orientation-induced zeolite imidazole metal-organic frameworks (ZIF-67) with thimbleful platinum doping. The introduction of melamine can reactivate adjacent carbon atoms and initiate the oriented growth of nitrogen-doped carbon nanotubes. The systematic analysis suggests the significant role of thimbleful neighboring low-coordinated Pt─N2 in altering the localized electronic structure of PtCo nanoclusters. The optimized PtSA -PtCo NCs/N-CNTs-900 exhibit excellent hydrogen evolution reaction (HER)/oxygen evolution reaction (OER)/oxygen reduction reaction (ORR)/ catalytic performance reaching the current density of 10 mA cm-2 in 1 m KOH under the low 47 (HER) and 252 mV (OER) overpotentials, and a high half-wave potential of 0.86 and 0.89 V (ORR) in 0.1 m KOH and 0.1 m HClO4 , respectively. Remarkably, the PtSA -PtCo NC/N-CNT-900 also presents outstanding catalytic performances toward water splitting and rechargeable Zn-air batteries. The theoretical calculations reveal that optimal regulation of the electronic structure of PtCo nanoclusters by thimbleful neighboring Pt atomic reduces the reaction energy barrier in electrochemical process, facilitating the ORR/OER/HER performance.

Atomically precise ultrasmall copper cluster for room-temperature highly regioselective dehydrogenative coupling

Three-component dehydrogenative coupling reactions represent important and practical methodologies for forging new C-N bonds and C-C bonds. Achieving highly all-in-one dehydrogenative coupling functionalization by a single catalytic system remains a great challenge. Herein, we develop a rigid-flexible-coupled copper cluster [Cu3(NHC)3(PF6)3] (Cu3NC(NHC)) using a tridentate N-heterocyclic carbene ligand. The shell ligand endows Cu3NC(NHC) with dual attributes, including rigidity and flexibility, to improve activity and stability. The Cu3NC(NHC) is applied to catalyze both highly all-in-one dehydrogenative coupling transformations. Mechanistic studies and density functional theory illustrate that the improved regioselectivity is derived from the low energy of ion pair with copper acetylide and endo-iminium ions and the low transition state, which originates from the unique physicochemical properties of the Cu3NC(NHC) catalyst. This work highlights the importance of N-heterocyclic carbene in the modification of copper clusters, providing a new design rule to protect cluster catalytic centers and enhance catalysis.

Chiral Hydride Cu18 Clusters Transform to Superatomic Cu15Ag4 Clusters: Circularly Polarized Luminescence Lighting

The manipulation of metal cluster enantiomers and their reconstruction remain challenging. Here, for the first time, we report an enantiomeric pair of hydride copper clusters [Cu18H(R/S-PEA)12](BF4)5 (R/S-Cu18H) made using designed chiral ligands. By manipulation of R/S-Cu18H with Ag+ ions, H- ions are released, leading to the reconstruction of 15 Cu atoms. Moreover, 4 Ag atoms replaced Cu atoms at the specific sites, resulting in the formation of homochiral [Cu15Ag4(R/S-PEA)12](BF4)5 (R/S-Cu15Ag4) with an isomorphic metal skeleton. This process was accompanied by a reduction reaction generating two free valence elections in the chiral alloying counterparts, which displayed orange emission. The solid-state R/S-Cu15Ag4 exhibited a photoluminescence quantum yield of 7.02% and excellent circularly polarized luminescence. The chiral transformations were resolved by single-crystal X-ray diffraction. The development of chiral copper hydride precursor-based metal clusters with chiroptical activities holds tremendous promise for advancing the field of optoelectronics and enabling new applications in lighting, displays, and beyond.

High Performance Dynamic X-ray Flexible Imaging Realized Using a Copper Iodide Cluster-Based MOF Microcrystal Scintillator

X-ray imaging technology has achieved important applications in many fields and has attracted extensive attentions. Dynamic X-ray flexible imaging for the real-time observation of the internal structure of complex materials is the most challenging type of X-ray imaging technology, which requires high-performance X-ray scintillators with high X-ray excited luminescence (XEL) efficiency as well as excellent processibility and stability. Here, a macrocyclic bridging ligand with aggregation-induced emission (AIE) feature was introduced for constructing a copper iodide cluster-based metal-organic framework (MOF) scintillator. This strategy endows the scintillator with high XEL efficiency and excellent chemical stability. Moreover, a regular rod-like microcrystal was prepared through the addition of polyvinyl pyrrolidone during the in situ synthesis process, which further enhanced the XEL and processibility of the scintillator. The microcrystal was used for the preparation of a scintillator screen with excellent flexibility and stability, which can be used for high-performance X-ray imaging in extremely humid environments. Furthermore, dynamic X-ray flexible imaging was realized for the first time. The internal structure of flexible objects was observed in real time with an ultrahigh resolution of 20 LP mm-1 .

Development of Au8 nanocluster-based fluorescent strip immunosensor for sensitive detection of aflatoxin B1

Gold clusters with intriguing chemical/physical properties have great promise in applications such as sensing and bio-imaging due to their fascinating photoluminescence character. In this study, an immunofluorescence sensor based on levonorgestrel protected atomically precise Au₈ nanocluster (Au₈NC) for aflatoxin B₁ (AFB₁) detection was fabricated due to its strong carcinogenic and mutagenic effect on humans. The prepared polymer-Au₈NC nanospheres displayed bright luminescence and good stability in aqueous solution. The obtained AFB₁ fluorescent strip immunosensor achieved quantitative point-of-care detection of AFB₁ in less than 15 min, with high selectivity and detection limits down to 0.27 ng/mL. In addition, the recovery rates of AFB₁ from tea soup ranged from 96% to 105% with relative standard deviations less than 10%. This work not only realized high-sensitively fluorescent sensing for AFB₁, but also expanded the bio-applications of atomic-precise metal clusters.

Multiple Stimuli-Responsive Luminescent Chiral Hybrid Antimony Chlorides for Anti-Counterfeiting and Encryption Applications

Stimuli-responsive circularly polarized luminescence (CPL) materials are ideal for information anti-countering applications, but the best-performing materials have not yet been identified. This work presents enantiomorphic hybrid antimony halides R-(C5 H12 NO)2 SbCl5 (1) and S-(C5 H12 NO)2 SbCl5 (2) showing mirror-imaged CPL activity with a dissymmetry factor of 1.2×10-3 . Interestingly, the DMF-induced structural transformation is realized to obtain non-emissive R-(C5 H12 NO)2 SbCl5  ⋅ DMF (3) and S-(C5 H12 NO)2 SbCl5  ⋅ DMF (4) upon exposure to DMF vapor. The transformation process is reversed upon heating. DFT calculations showed that the DMF-induced-quenched-luminescence is attributed to the intersection of the ground and excited state curves on the configuration coordinates. Unexpectedly, the nanocrystals of the chiral antimony halides 1 and 2 were prepared and indicate the excellent solution process performance. The reversible PL and CPL switching gives the system applications in information technology, anti-counterfeiting, encryption-decryption, and logic gates.

Multi-Stimuli-Responsive Chromic Behaviors of an All-in-One Viologen-Based Cd(II) Complex

A one-dimensional Cd(II) chain coordination polymer constructed by an electron-deficient viologen-anchored carboxylate ligand was successfully synthesized. Owing to the favorable stimuli-chromic properties of viologen, the title compound shows reversible photochromism, thermochromism, electrochromism, and naked-eye-detectable differentiable vapochromic response to different volatile amines. The chromic behaviors of it are ascribed to the formation of viologen radicals triggered by external stimuli. And the differentiated response to volatile amines is attributed to the size effect of the amines as well as the steric hindrance effect of forming α/β Cv-H···Namines interactions of the viologen unit to further affect the occurrence of electron transfer. Such an all-in-one crystalline material might have more practical applications in photoelectric, erasable inkless printing, light printing, and volatile amine detection fields.

Electrocatalytic Mechanism of Defect in Spinels for Water and Organics Oxidation

Spinels display promising electrocatalytic ability for oxygen evolution reaction (OER) and organics oxidation reaction because of flexible structure, tunable component, and multifold valence. Unfortunately, limited exposure of active sites, poor electronic conductivity, and low intrinsic ability make the electrocatalytic performance of spinels unsatisfactory. Defect engineering is an effective method to enhance the intrinsic ability of electrocatalysts. Herein, the recent advances in defect spinels for OER and organics electrooxidation are reviewed. The defect types that exist in spinels are first introduced. Then the catalytic mechanism and dynamic evolution of defect spinels during the electrochemical process are summarized in detail. Finally, the challenges of defect spinel electrocatalysts are brought up. This review aims to deepen the understanding about the role and evolution of defects in spinel for electrochemical water/organics oxidation and provide a significant reference for the design of efficient defect spinel electrocatalysts.

Photoluminescence Anisotropy in Eutectic Crystals of Polynuclear Lanthanide Complexes and Silver Clusters

Anisotropy is an intrinsic property of crystalline materials. However, the photoluminescence anisotropy in eutectic crystals of organometallic complexes has remained unexplored. Herein, the eutectic of polynuclear lanthanide complexes and Ag clusters was prepared, and the crystal shows significant photoluminescence anisotropy. The polarization anisotropy of emission δ and degree of excitation polarization P are 2.62 and 0.53, respectively. The rare excitation polarization properties have been proved to be related to the regular arrangement of electric transition dipole moments of luminescent molecules in the crystal. Our design provides a reference for developing new photoluminescence anisotropy materials and expanding their applications.

Aggregation-Induced Emission (AIE), Life and Health

Light has profoundly impacted modern medicine and healthcare, with numerous luminescent agents and imaging techniques currently being used to assess health and treat diseases. As an emerging concept in luminescence, aggregation-induced emission (AIE) has shown great potential in biological applications due to its advantages in terms of brightness, biocompatibility, photostability, and positive correlation with concentration. This review provides a comprehensive summary of AIE luminogens applied in imaging of biological structure and dynamic physiological processes, disease diagnosis and treatment, and detection and monitoring of specific analytes, followed by representative works. Discussions on critical issues and perspectives on future directions are also included. This review aims to stimulate the interest of researchers from different fields, including chemistry, biology, materials science, medicine, etc., thus promoting the development of AIE in the fields of life and health.

Regulation of Electrocatalytic Behavior by Axial Oxygen Enhances the Catalytic Activity of CoN4 Sites for CO2 Reduction

Recent studies have found that the existence of oxygen around the active sites may be essential for efficient electrochemical CO2 -to-CO conversion. Hence, this work proposes the modulation of oxygen coordination and investigates the as-induced catalytic behavior in CO2 RR. It designs and synthesizes conjugated phthalocyanine frameworks catalysts (CPF-Co) with abundant CoN4 centers as an active source, and subsequently modifies the electronic structure of CPF-Co by introducing graphene oxide (GO) with oxygen-rich functional groups. A systematic study reveals that the axial coordination between oxygen and the catalytic sites could form an optimized O-CoN4 structure to break the electron distribution symmetry of Co, thus reducing the energy barrier to the activation of CO2 to COOH*. Meanwhile, by adjusting the content of oxygen, the proper supports can also facilitate the charge transfer efficiency between the matrix layer and the catalytic sites. The optimized CPF-Co@LGO exhibits a high TOF value (2.81 s-1 ), CO selectivity (97.6%) as well as stability (24 h) at 21 mA cm-2 current density. This work reveals the modulation of oxygen during CO2 RR and provides a novel strategy for the design of efficient electrocatalysts, which may inspire new exploration and principles for CO2 RR.

Thermally Activated Delayed Fluorescence Coinage Metal Cluster Scintillator

X-ray scintillators are widely used in medical imaging, industrial flaw detection, security inspection, and space exploration. However, traditional commercial scintillators are usually associated with a high use cost because of their substantial toxicity and easy deliquescence. In this work, an atomically precise Au-Cu cluster scintillator (1) with a thermally activated delayed fluorescence (TADF) property was facilely synthesized, which is environmentally friendly and highly stable to water and oxygen. The TADF property of 1 endows it with an ultrahigh exciton utilization rate. Combined with the effective absorption of X-ray caused by the heavy-atom effect and a limited nonradiative transition caused by close packing in the crystal state, 1 exhibits an excellent radioluminescence property. Moreover, 1 has good processability for fabricating a large, flexible thin-film device (10 cm × 10 cm) for high-resolution X-ray imaging, which can reach 40 μm (12.5 LP mm^-1). The properties mentioned earlier make the coinage metal cluster promising for use as a substitute for traditional commercial scintillators.

Atomically precise chiral silver clusters based on non-chiral ligands for acid/base stimulated luminescence response

Chiral metal nanoclusters synthesized by non-chiral ligands are usually in the form of racemates. Thus, resolving racemic compounds continues to be a great challenge. Herein, we report a case of the racemic compound hexanuclear silver cluster (Ag6-Rac) protected by the non-chiral sulfhydryl ligand sodium 1H-1,2,3-triazole-5-thiolate (SHTT) and 2,6-bis(diphenylphosphino)pyridine (dpppy). The homochiral clusters in Ag6-Rac are able to spontaneously crystallize and undergo chiral resolution to obtain a racemic conglomerate (Ag6-S/Ag6-R) by solvent-induced crystallization. Interestingly, the Ag6-Rac clusters exhibit strong luminescence in solid and solution, which can respond to trifluoroacetic acid (TFA) and reversible cycling over five times using diethylamine (DEA). This work provides a new research model for resolving racemic clusters and constructing stimulus-responsive clusters.

Carbene-stabilized enantiopure heterometallic clusters featuring EQE of 20.8% in circularly-polarized OLED

Bright and efficient chiral coinage metal clusters show promise for use in emerging circularly polarized light-emitting materials and diodes. To date, highly efficient circularly polarized organic light-emitting diodes (CP-OLEDs) with enantiopure metal clusters have not been reported. Herein, through rational design of a multidentate chiral N-heterocyclic carbene (NHC) ligand and a modular building strategy, we synthesize a series of enantiopure Au(I)-Cu(I) clusters with exceptional stability. Modulation of the ligands stabilize the chiral excited states of clusters to allow thermally activated delayed fluorescence, resulting in the highest orange-red photoluminescence quantum yields over 93.0% in the solid state, which is accompanied by circularly polarized luminescence. Based on the solution process, a prototypical orange-red CP-OLED with a considerably high external quantum efficiency of 20.8% is prepared. These results demonstrate the extensive designability of chiral NHC ligands to stabilize polymetallic clusters for high performance in chiroptical applications.

Substituent Effect to Fine-Tune Energy Levels of Atom-Precise [MoOS3]2- Modified Cu(I) Thiolate Clusters Boosting Recyclable Photocatalysis

The propulsion of photocatalytic hydrogen (H2) production is limited by the rational design and regulation of catalysts with precise structures and excellent activities. In this work, the [MoOS3]2- unit is introduced into the Cu(I) clusters to form a series of atomically-precise Mo(VI)-Cu(I) bimetallic clusters of [Cu6(MoOS3)2(C6H5(CH2)S)2(P(C6H4-R)3)4]·xCH3CN (R = H, CH3, or F), which show high photocatalytic H2 evolution activities and excellent stability. By electron push-pull effects of the surface ligand, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of these Mo(VI)-Cu(I) clusters can be finely tuned, promoting the resultant visible-light-driven H2 evolution performance. Furthermore, Mo(VI)-Cu(I) clusters loaded onto the surface of magnetic Fe3O4 carriers significantly reduced the loss of catalysts in the collection process, efficiently addressing the recycling issues of such small cluster-based catalyst. This work not only highlights a competitively universal approach on the design of high-efficiency cluster photocatalysts for energy conversion, but also makes it feasible to manipulate the catalytic performance of clusters through a rational substituent strategy.

Predesigned Cluster-Based Spacers for Versatile Luminescent Metallacages

Luminescent metal-organic cages are of great interest in contemporary research; however, their designed synthesis remains challenging. Here, we created metal-cluster-derived spacers, where emissive C₃-symmetric Cu₄ clusters have three arms modified by benzene alkynyl ligands, which are terminally functionalized by extensile -COOH and 15-crown-5-ether groups with directional coordination ability. Through vertex orientation, -COOH-functionalized cluster-based spacers coassembled with paddle-wheel Cu(I)_xZn(II)_2-x(COO)₃ nodes in 3+3 mode, generating an emissive cubic cage, which subsequently gave another distorted cubic cage by synthetic modification on the nodes. Through face orientation, 15-crown-5-ether-containing cluster-based spacers capturing K⁺ ions in 3+2 mode produced an octahedral cage whose empty phase showed dual emission peaks, leading to diverse stimuli-responsive photoluminescence. This work provides new design and synthesis strategies for the integration of nodes and spacers based on metal clusters for cage materials as well as prototypes of luminescent metal-cluster cages for important sensing applications.

Regulating structural asymmetry via fluorination engineering in hybrid lead bromide perovskites

Here, we synthesized a pair of chiral two-dimensional lead bromide perovskites R-/S-(C₃H₇NF₃)₂PbBr₄ (1R/2S) using a H/F substitution strategy, which exhibit circular dichroism (CD) and circularly polarized luminescence (CPL) activity. Compared with one-dimensional non-centrosymmetric (C₃H₁₀N)₃PbBr₅ with local asymmetry obtained by isopropylamine, 1R/2S show a centrosymmetric inorganic layer despite the global chiral space group. Density functional theory calculations show that the formation energy of 1R/2S is lower than that of (C₃H₁₀N)₃PbBr₅, which implies the improved moisture stability in photophysical properties and CPL activity.

Constructing Highly Reliable and Adaptive Primary Explosive Composites for Micro-Initiator Assisting by a Hybrid Template of Metal-Organic Frameworks and Cross-Linked Polymers

Primary explosive, as a reliable initiator for secondary explosives, is the central component of micro-initiators for modern aerospace systems and military operations. However, they are typically prepared as powders, posing potential safety risks because of the inevitable particles scattering issues in the actual working environments. Here, the fabrication of a highly adaptive bulk material of copper azide (CA)-based safe primary explosive for micro-initiators is demonstrated. This bulk material, as derived by a complete azidation reaction of the carbonized metal-organic framework/cross-linked polymer hybrid template, enables the firm embedding of active CA species in a cross-linked carbon network (denoted as CA-C). Interestingly, this CA-C bulk material demonstrates multifarious mechanical stabilities (e.g., good shock and vibration resistance, and anti-overload capacity) in the simulated working conditions. Meanwhile, the CA contents in the CA-C bulk material reached as high as 70.3%, ensuring its detonation power. As a proof of concept, CA-C bulk material assembling in a micro-detonator can efficiently detonate the secondary explosive of CL-20 under laser irradiation. This work hereby advances the fabrication of safe and powerful primary explosives for the fulfillment of safe micro-initiator in a broad range of applications in aerospace systems.

Stepwise Amplification of Circularly Polarized Luminescence in Chiral Metal Cluster Ensembles

Chiral metal-organic frameworks (MOFs) are usually endowed by chiral linkers and/or guests. The strategy using chiral secondary building units in MOFs for solving the trade-off of circularly polarized luminescence (CPL)-active materials, high photoluminescence quantum yields (PLQYs) and high dissymmetry factors (|g_lum |) has not been demonstrated. This work directionally assembles predesigned chiral silver clusters with ACQ linkers through reticular chemistry. The nanoscale chirality of the cluster transmits through MOF's framework, where the linkers are arranged in a quasi-parallel manner and are efficiently isolated and rigidified. Consequently, this backbone of chiral cluster-based MOFs demonstrates superb CPL, high PLQYs of 50.3%, and |g_lum | of 1.2 × 10^-2 . Crystallographic analyses and DFT calculations show the quasi-parallel arrangement manners of emitting linkers leading to a large angle between the electric and magnetic transition dipole moments, boosting CPL response. As compared, an ion-pair-direct assembly without interactions between linkers induces one-ninth |g_lum | and one-sixth PLQY values, further highlighting the merits of directional arrangement in reticular nets. In addition, a prototype CPL switching fabricated by a chiral framework is controlled through alternating ultraviolet and visible light. This work is expected to inspire the development of reticular chemistry for high-performance chiroptical materials.

Water-Soluble Au25 Clusters with Single-Crystal Structure for Mitochondria-Targeting Radioimmunotherapy

Atomically precise gold clusters play an important role in the development of high-Z-element-based radiosensitizers, due to their intriguing structural diversity and advantages in correlating structures and properties. However, the synthesis of gold clusters with both water-solubility and single-crystal structure remains a challenge. In this study, atomically precise Au₂₅(S-TPP)₁₈ clusters (TPP-SNa = sodium 3-(triphenylphosphonio)propane-1-thiolate bromide) showing both mitochondria-targeting ability and water-solubility were obtained via ligand design for enhanced radioimmunotherapy. Compared with Au₂₅(SG)₁₈ clusters (SG = glutathione), Au₂₅(S-TPP)₁₈ exhibited higher radiosensitization efficiency due to its mitochondria-targeting ability, higher ROS production capacity, and obvious inhibition upon thioredoxin reductase (TrxR). In addition, the enhanced radiotherapy-triggered abscopal effect in combination with checkpoint blockade displayed effective growth inhibition of distant tumors. This work reveals the ligand-regulated organelle targeting ability of metal clusters by which feasible strategies to promote their application in precise theranostics could be realized.

Chirality-Dependent Structural Transformation in Chiral 2D Perovskites under High Pressure

Chiral perovskites have attracted considerable attention owing to their potential applications in spintronic- and polarization-based optoelectronic devices. However, the structural chirality/asymmetry transfer mechanism between chiral organic ammoniums and achiral inorganic frameworks is still equivocal, especially under extreme conditions, as the systematic structural differences between chiral and achiral perovskites have been rarely explored. Herein, we successfully synthesized a pair of new enantiomeric chiral perovskite (S/R-3PYEA)PbI₄ (3PYEA²⁺ = C₅NH₅C₂H₄NH₃²⁺) and an achiral perovskite (rac-3PYEA)PbI₄. Hydrostatic pressure was used, for the first time, to systematically investigate the differences in the structural evolution and optical behavior between (S/R-3PYEA)PbI₄ and (rac-3PYEA)PbI₄. At approximately 7.0 GPa, (S/R-3PYEA)PbI₄ exhibits a chirality-dependent structural transformation with a bandgap "red jump" and dramatic piezochromism from translucent red to opaque black. Upon further compression, a previously unreported chirality-induced negative linear compressibility (NLC) is achieved in (S/R-3PYEA)PbI₄. High-pressure structural characterizations and first-principles calculations demonstrate that pressure-driven homodirectional tilting of homochiral ammonium cations strengthens the interactions between S/R-3PYEA²⁺ and Pb-I frameworks, inducing the formation of new asymmetric hydrogen bonds N-H···I-Pb in (S/R-3PYEA)PbI₄. The enhanced asymmetric H-bonding interactions further break the symmetry of (S/R-3PYEA)PbI₄ and trigger a greater degree of in-plane and out-of-plane distortion of [PbI₆]^4- octahedra, which are responsible for chirality-dependent structural phase transition and NLC, respectively. Nevertheless, the balanced H-bonds incurred by equal proportions of S-3PYEA²⁺ and R-3PYEA²⁺ counteract the tilting force, leading to the absence of chirality-dependent structural transition, spectral "red jump", and NLC in (rac-3PYEA)PbI₄.

A pyrolysis-free Ni/Fe bimetallic electrocatalyst for overall water splitting

Catalysts capable of electrochemical overall water splitting in acidic, neutral, and alkaline solution are important materials. This work develops bifunctional catalysts with single atom active sites through a pyrolysis-free route. Starting with a conjugated framework containing Fe sites, the addition of Ni atoms is used to weaken the adsorption of electrochemically generated intermediates, thus leading to more optimized energy level sand enhanced catalytic performance. The pyrolysis-free synthesis also ensured the formation of well-defined active sites within the framework structure, providing ideal platforms to understand the catalytic processes. The as-prepared catalyst exhibits efficient catalytic capability for electrochemical water splitting in both acidic and alkaline electrolytes. At a current density of 10 mA cm^-2, the overpotential for hydrogen evolution and oxygen evolution is 23/201 mV and 42/194 mV in 0.5 M H₂SO₄ and 1 M KOH, respectively. Our work not only develops a route towards efficient catalysts applicable across a wide range of pH values, it also provides a successful showcase of a model catalyst for in-depth mechanistic insight into electrochemical water splitting.

Highly Efficient Circularly Polarized Luminescence from Chiral Au13 Clusters Stabilized by Enantiopure Monodentate NHC Ligand

Chiral Au nanoclusters have promising application prospects in chiral sensing, asymmetric catalysis, and chiroptics. However, enantiopure superatomic homogold clusters with crystallographic structures emitting bright circularly polarized luminescence (CPL) remain challenging. In this study, we designed chiral N-heterocyclic carbenes (NHCs), and for the first time enantioselectively synthesized a pair of monovalent cationic superatomic Au13 clusters. This new enantiomeric pair of clusters has a quasi-C2 symmetric core and exhibited CPL with an unprecedent solution-state quantum yield (QY) of 61% among those of the atomically precise Au nanoclusters. DFT calculations provided insights into the circular dichroism behavior, and revealed the origin of CPL from superatomic Au clusters. This work opens a new avenue for developing novel homochiral nanoclusters using chiral NHC ligands and provides fundamental understanding of the origin of the chiroptics of metal clusters.

Cocrystallization of Two Negatively Charged Dimercaptomaleonitrile-Stabilized Silver Nanoclusters

Studies on the assembly of atomically precise metal nanoclusters (NCs) are of great significance in the nanomaterial field, which has attracted increasing interest in the last few decades. Herein, we report the cocrystallization of two negatively charged atom-precise silver nanoclusters, the octahedral [Ag₆₂(MNT)₂₄(TPP)₆]^8- (Ag₆₂) and the truncated-tetrahedral [Ag₂₂(MNT)₁₂(TPP)₄]^4- (Ag₂₂) in a 1:2 ratio (MNT^2- = dimercaptomaleonitrile, TPP = triphenylphosphine). As far as we know, a cocrystal containing two negatively charged NCs has seldom been reported. Single-crystal structure determinations reveal that the component Ag₂₂ and Ag₆₂ NCs both adopt core-shell structures. In addition, the component NCs were separately obtained by adjusting the synthetic conditions. This work enriches the structural diversity of silver NCs and extends the family of cluster-based cocrystals.

Smart Reversible Transformations between Chiral Superstructures of Copper Clusters for Optical and Chiroptical Switching

Superstructures made from nanoscale clusters with new collective properties are promising in high-tech applications; however, chiral superstructures remain elusive, and the limited intercluster coupling effect at room temperature hampers the tailoring of collective properties. Here, we show that from chiral monomeric copper clusters to two enantiomeric pairs of supercrystals with distinct phases, the absorption band edge red-shifts by over 1.3 eV, with photoluminescence and circularly polarized phosphorescence from visible (572 nm) to near-infrared (NIR, 858 nm). These supercrystals with high NIR quantum yields of up to 45% at room temperature are prototyped for night-vision imaging. In response to solvent and temperature stimuli, chiral supercrystal-to-supercrystal transformations occurred, concomitant with high-contrast optical/chiroptical switching. In situ single-crystal X-ray diffraction (SCXRD), steady-state and time-resolved optical spectroscopy, and response experiments combined with theoretical calculations demonstrate that distance-sensitive intercluster orbital interactions contribute to the exceptional collective optical responses. Such chiral supercrystals built from subnanoscale metal clusters with novel collective chiroptical responses would be useful in the fields of information storage and NIR optical devices.