A³ coupling reaction is a three-component reaction widely used in pharmaceutical and is an important and practical method for constructing new C-N and C-C bonds. Here, two low-Nuclear Cu₄Cl₂/C₃N₄ and Cu₂Cl₄/C₃N₄ catalysts were specifically designed for A³ coupling under mild conditions, with TON up to 8702.3 and 3461.8, respectively, much higher than reported catalysts. Additionally, we captured the key intermediate and confirmed its structures by ESI, revealing the halogen exchange process at the atomic level by experiments and DFT studies. These results increase our understanding of low-nuclear catalysts and provide guidance for the design and preparation of more efficient and targeted catalytic materials.

Metal-organic frameworks (MOFs) have emerged as superior hosting matrices for atomically precise nanoclusters (NCs) encapsulation, offering excellent physical and chemical protections for advanced catalysis. Nevertheless, the MOF coating significantly reduces the NC catalytic efficiency due to the diffusion barriers and the confined microenvironments. Herein, a hierarchically engineered MOF nanoreactor was constructed by controlled structural etching for NC immobilization. This nanoreactor possesses hierarchical pores to accelerate the diffusion rate of reactants and creates hollow structures to unleash the confined NC molecules from the rigid MOF network to a capacious microenvironment. The enhanced mass transfer, improved freedom of NCs, and outstanding stability collectively boosted the catalytic activity of the nanoreactor. By controlling the etching time, freestanding Pd₈@zeolitic imidazolate framework-8 (ZIF-8)-TA₁₀ displayed a catalytic efficiency that was 3.17 times greater than that of the initial confined Pd₈@ZIF-8 and even better than free Pd₈. This work opens a new strategy to reduce the inherent limitations of porous matrixes for developing high-performance catalysts.

Carbon-supported noble-metal-free single-atom catalysts (SACs) have aroused widespread interest due to their green chemistry aspects and excellent performances. Herein, we propose a “ligand regulation strategy” and achieve the successful fabrication of bifunctional SAC/MOF (MOF = metal–organic framework) nanocomposite (abbreviated NiSA/ZIF-300; ZIF = ZIF-8) with exceptional catalytic performance and robustness. The designed NiSA/ZIF-300 has a planar interfacial structure with the Ni atom, involving one S and three N atoms bonded to Ni(II), fabricated by controllable pyrolysis of volatile Ni-S fragments. For CO₂ cycloaddition to styrene epoxide, NiSA/ZIF-300 exhibits ultrahigh activity (turnover number (TON) = 1.18 × 10⁵; turnover frequency (TOF) = 9830 mol_SC·mol_Ni⁻¹·h⁻¹; SC = styrene carbonate) and durability at 70 °C under 1 atm CO₂ pressure, which is much superior to Ni complex/ZIF, NiNP/ZIF-300, and most reported catalysts. This study offers a simple method of bifunctional SAC/MOF nanocomposite fabrication and usage, and provides guidance for the precise design of additional original SACs with unique catalytic properties.

Bimetallic nanocluster with atomic precision has gained widespread attention due to its unique synergism. The coreless Au₄Cu₅ bimetallic nanoclusters were selected as models to explore the relationship between their microstructure and performance, and compare with the coreless monometallic nanoclusters, core–shell nanoclusters, and single atom catalyst (SAC). The experimental results show that the coreless bimetallic nanocluster catalyst Au₄Cu₅/activated carbon (AC) exhibits high activity and stability in the Ullmann C–O coupling reaction, much higher than coreless monometallic nanoclusters (Au₁₁/AC and Cu₁₁/AC), core–shell nanoclusters (Au₂₅/AC, Cu₂₅/AC, and Au₁Cu₂₄/AC), and single atom catalysts (Au SAC and Cu SAC). Moreover, the coreless Au₄Cu₅/AC catalyst efficiently catalyzed the Ullmann C–O coupling of benzyl alcohol for the first time. This structure–activity relationship was successfully extended to other coreless bimetallic systems, such as Au₄Cu₄/AC nanocluster, and it is expected to provide new insights for the design of bimetallic catalysts with well-defined performance.