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.

Hierarchical assembly of Ag40 nanowheel ranging from building blocks to diverse superstructure regulation

Achieving precise and controllable hierarchical self-assembly of functional nanoclusters within crystal lattices to create distinct architectures is of immense significance, yet it creates considerable challenges. Here we successfully synthesized a silver nanowheel Ag40, along with its optically pure enantiomers S-/R-Ag40. Each species possesses an internal nanospace and exhibits host-guest interactions. These structures are constructed from primary building blocks (Ag9). By manipulating the surface anions and guest molecules, the nanowheels function as secondary building blocks, spontaneously organizing into complex double- and triple-helical crystalline superstructures or one-dimensional chains {Ag41}n through conformational matching and diverse noncovalent interactions. Moreover, we demonstrate that the water-mediated complex specifically assembled with uridine monophosphate nucleotides, resulting in chiral assemblies of Ag40 that exhibit chiroptical activity for specific recognition. Our findings provide insights into the efficient construction of assemblies with hollow frameworks and propose strategies for superstructure engineering by manipulating surface motifs.

Phosphate anion-induced silver-chalcogenide cluster-based metal organic frameworks as dual-functional catalysts for detoxifying chemical warfare agent simulants

Two porphyrinic silver-chalcogenide cluster-based MOFs were achieved using a phosphate anionic template strategy, and the highly photoactive organic building modules combined with Lewis acidic silver clusters allow both SCC-MOFs to be used as versatile catalysts for the simultaneous degradation of sulfur mustard and nerve agent simulants.

3D Cluster-Based Covalent Organic Framework for Efficient CO2 Photoreduction

Copper clusters exhibit superior catalytic activity for the CO2 reduction reaction (CO2RR), and their defined structures endow them with unique advantages for modeling the catalytic mechanism at the atomic level. Additionally, the construction of highly stable and regularly structured covalent organic frameworks (COFs) based on copper clusters still presents significant challenges. Herein, we reported two highly stable and reactive cluster-based COFs (termed Cu4COF-1 and Cu4COF-2) constructed via a stepwise assembly strategy. The epitaxially amino-modified Cu4 cluster (Cu4-NH2) was initially synthesized based on coordination bonds. Then, Cu4COFs were obtained by the covalent linkage of Cu4-NH2 clusters and organic linkers. Compared with isolated Cu4 clusters, the Cu4COFs exhibit greater stability, a narrower band gap, a larger specific surface area, and better charge transfer ability, which endow them with superior photocatalytic CO2RR performance under visible light. In-situ infrared spectroscopy and density functional theory (DFT) calculations revealed that the covalently linked Cu4COFs could efficiently lower the energy barrier for the formation of the critical *COOH intermediate, thereby enhancing the photocatalytic activity. This study offers a solid basis for the atomically precise construction of novel metal-cluster-based COF catalysts.