Atomically precise single-atom catalysts (SACs) are essential for establishing reliable structure-activity relationships, yet synthetic routes that afford SACs with fully resolved coordination microenvironments remain a significant challenge. Here we report a secondary building unit (SBU) deconstruction-reorganization strategy that converts the dicopper Cu2(COO)4 cluster in Cu2(TCA)4/3 (H3TCA = 4,4',4″-tricarboxytriphenylamine) framework into a Y4(μ3-OH)4Cu2(COO)12 heterometallic cluster through the introduction of Y3+ and 2-fluorobenzoic acid modulator. Single-crystal X-ray diffraction unambiguously captures this reorganization, which expands the Cu···Cu distance from 2.6 to 10.3 Å, generates two isolated square CuO4 sites, and preserves the spatial arrangement of all TCA linkers with minimal lattice perturbation. The resulting framework, CCNUF-51, adopts a (3,8)-connected the topology arising from merging two adjacent 4-connected paddlewheel nodes of the parent pto net into a single 8-connected node. CCNUF-51 exhibits good chemical stability (pH 2-12), attributed to the synergistic coordination of hard Y3+ and soft Cu2+ within the heterometallic SBU. The atomically dispersed Cu sites are intimately coupled to photoactive TCA linkers, enabling highly efficient photocatalytic benzylic C(sp3)-H functionalization─including esterification, sulfonamidation, and methoxylation─that outperforms CuI, Cu(OAc)2, Cu2(TCA)4/3, and benchmark Cu/UiO-66 SAC. This work establishes SBU deconstruction-reorganization as an effective route for accessing SACs with atomically well-defined active sites.
Yuan et al. (Wed,) studied this question.