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Single-atom catalysts (SACs), featuring high atom utilization, have captured widespread interests in diverse applications. However, the singleatom sites in SACs are generally recognized as independent units and the interplay of adjacent sites is largely overlooked. Herein, by the direct pyrolysis of MOFs assembled with Fe and Ni-doped ZnO nanoparticles, a novel Fe 1 − Ni 1 −N−C catalyst, with neighboring Fe and Ni single-atom pairs decorated on nitrogen-doped carbon support, has been precisely constructed. Thanks to the synergism of neighboring Fe and Ni single-atom pairs, Fe 1 −Ni 1 −N−C presents significantly boosted performances for electrocatalytic reduction of CO 2 , far surpassing Fe 1 −N−C and Ni 1 −N−C with separate Fe or Ni single atoms. Additionally, the Fe 1 −Ni 1 −N−C also exhibits superior performance with excellent CO selectivity and durability in Zn-CO 2 battery. Theoretical simulations reveal that, in Fe 1 −Ni 1 −N−C, single Fe atoms can be highly activated by adjacent single-atom Ni via non-bonding interaction, significantly facilitating the formation of COOH* intermediate and thereby accelerating the overall CO 2 reduction. This work supplies a general strategy to construct single-atom catalysts containing multiple metal species and reveals the vital importance of the communitive effect between adjacent single atoms toward improved catalysis.

Rh-based heterogeneous catalysts generally have limited selectivity relative to their homogeneous counterparts in hydroformylation reactions despite of the convenience of catalyst separation in heterogeneous catalysis. Here, we develop CoO-supported Rh single-atom catalysts (Rh/CoO) with remarkable activity and selectivity towards propene hydroformylation. By increasing Rh mass loading, isolated Rh atoms switch to aggregated clusters of different atomicity. During the hydroformylation, Rh/CoO achieves the optimal selectivity of 94.4% for butyraldehyde and the highest turnover frequency number of 2,065 h−1 among the obtained atomic-scale Rh-based catalysts. Mechanistic studies reveal that a structural reconstruction of Rh single atoms in Rh/CoO occurs during the catalytic process, facilitating the adsorption and activation of reactants. In kinetic view, linear products are determined as the dominating products by analysing reaction paths deriving from the two most stable co-adsorbed configurations. As a bridge of homogeneous and heterogeneous catalysis, single-atom catalysts can be potentially applied in other industrial reactions.

Atomically dispersed metal catalysts maximize atom e ciency and display unique catalytic properties compared to regular metal nanoparticles. However, achieving high reactivity while still preserving high stability at high loadings remains as a grand challenge. Here we solve the challenge by synergizing strong metal-support interactions and spatial con nement, which enable to fabricate highly loaded (3.1 wt%), active and stable atomic Ni and dense atomic Cu grippers (8.1 wt%) on a graphitic C 3 N 4 support.For semi-hydrogenation of acetylene in excess of ethylene, the fabricated catalyst shows 11 times higher activity than the atomic Ni alone, high ethylene selectivity (90%), and high stability against both sintering and coke formation for 350 h. Comprehensive microscopic and spectroscopic characterization and theoretical calculations reveal the active site of the bridging Ni con ned in two hydroxylated Cu grippers, whose structure changes dynamically by breaking interfacial Ni-support bonds upon reactant adsorption and making these bonds upon product desorption. Such a dynamic effect confers high activity/selectivity and high stability, providing an avenue to rational design of e cient, stable, highly loaded, yet atomically dispersed catalysts.