Dual-Metal Single Atoms with Dual Coordination for the Domino Synthesis of Natural Flavones.

The regulation of coordination configurations of single-atom sites is highly desirable to boost the catalytic performances of SA catalysts. Here, we demonstrate a versatile complexation-deposition strategy for the synthesis of 13 kinds of dual-metal SA site pairs with uniform and exclusive coordination configurations. The preparation is specifically exemplified by the fabrication of Cu and Co single-atom pairs with the co-existence of N and P heteroatoms through etching and pyrolysis of a pre-synthesized metal-organic framework template. Systematic characterizations reveal the uniform and exclusive coordinative configuration of Cu and Co SA sites in CuN/CoNP and CuN/CoNP, over which the electrons are unsymmetrically distributed. Impressively, the CuN/CoNP site pairs exhibit significantly enhanced catalytic activity and selectivity in the synthesis of a variety of natural flavonoids in comparison with the CuN/CoNP and CuN/CoN counterparts. Theoretical calculation results suggest that the unsymmetrical electron distribution over the CuN/CoNP sites could facilitate the adsorption and disassociation of oxygen molecules via reducing the energy barriers of the generation of the key intermediates and thus kinetically accelerate the oxidative-coupling reaction process.