Bi-atom active sites embedded in a two-dimensional covalent organic framework for efficient nitrogen reduction reaction

An economical and environment-friendly approach for N2 reduction reaction (NRR) under mild conditions is currently urgent. The development of single-atom catalysts (SACs) offers a new strategy for reaching this goal. However, the single active site of SAC makes limitation for achieving high NRR performance. The synergetic reaction centers in bi-atom catalysts (BACs) are proposed to further boost reaction activity. On the basis of a newly-synthesized two-dimensional (2D) binuclear Cu-salphen covalent organic framework (COF), we predict four promising BACs for NRR with transition metal (TM) atoms (TM = Fe, Co, Mo, W and Ru) embedded in this COF. The low limiting potentials (-0.29 to -0.57 V) and high theoretical Faradaic efficiency (FE) (76-100%) of these BACs can be correlated to the asymmetrical charge depletion of metal dimers and the synergistic effect between the metal atoms and the 2D COF. The thermal stability and realistic feasibility of M1M2-COFs were also assessed. Our work offers a group of promising candidates of ultra-efficient COF-based NRR BACs, as well as a rational guidance for catalyst design.