关键词: 多级孔MOF, 单原子铜位点, 氮杂环化合物, C—N偶联

Nitrogen heterocycles serve as key structural components in modern pharmaceutical, materials, and agrochemical applications. Addressing the intrinsic limitations of conventional C—N coupling catalysts—particularly their poor catalytic efficiency and narrow substrate range—this investigation engineered an advanced catalytic architecture based on an Al(BPY) metal-organic framework (MOF). The synthetic route involved: (1) hydrothermal assembly of microporous Al(BPY) MOF employing 2,2'-bipyridine (BPY, rigid bidentate N-ligand) and AlCl₃, followed by (2) controlled liquid-phase loading of Cu(BF₄)₂ as a bifunctional reagent (dual etchant and metal source). This innovative approach successfully accomplished two critical objectives concurrently: (i) in situ formation of hierarchically porous networks (pore size distribution: 1~50 nm) and (ii) atomic-level precision immobilization of mono-disperse copper active centers. Structural analysis showed $\text{BF}_{4}^{-}$ etches Al—O—C bonds forming mesopores, while Cu²⁺ coordinates with pyridinic N ensuring atomic dispersion. Rigorous evaluation of Al(BPY)-Cu(BF₄)₂'s catalytic behavior in Ullmann C—N coupling reactions established distinct structure-activity correlations, with the Cu(BF₄)₂-modified catalyst exhibiting substantially superior activity relative to Cu(NO₃)₂-, CuCl₂-, and Cu(acac)₂-modified analogs. The Al(BPY)-Cu(BF₄)₂-0.5 demonstrated optimal catalytic performance, achieving 93% product yield under optimized reaction parameters (Cs₂CO₃ base, dimethylsulfoxide solvent, 120 ℃, 16 h). Notably, the catalyst displayed exceptional functional group compatibility (55%~95% yields across 42 diverse substrates including fused-ring systems, non-aromatic N-heterocycles, and P—H compounds) while maintaining remarkable tolerance toward both electronic and steric perturbations. The system successfully transcended conventional catalytic constraints by accomplishing: (i) efficient coupling of sterically demanding non-aromatic amines and (ii) pioneering MOF-mediated C—P bond formation—the first documented instance of such transformation in MOF-based catalytic systems. Furthermore, the material exhibited outstanding cycling stability, retaining >94% initial activity through 8 successive reaction cycles with negligible copper leach-ing (<0.2 mg/L). The exceptional catalytic efficiency originates from synergistic interplay between hierarchically porous channels (facilitating enhanced mass transport and active site accessibility) and atomic Cu centers (activating aryl iodides and X—H bonds).

Key words: hierarchically porous MOF, single-atom copper sites, nitrogen heterocycles, C—N coupling