Regulating the Coordination Environment of MOF‐Templated Single‐Atom Nickel Electrocatalysts for Boosting CO 2 Reduction

The general synthesis and control of the coordination environment of single‐atom catalysts (SACs) remains a great challenge. Herein, a general host–guest cooperative protection strategy has been developed to construct SACs by introducing polypyrrole (PPy) into a bimetallic metal–organic framework. As an example, the introduction of Mg 2+ in MgNi‐MOF‐74 extends the distance between adjacent Ni atoms; the PPy guests serve as N source to stabilize the isolated Ni atoms during pyrolysis. As a result, a series of single‐atom Ni catalysts (named Ni SA ‐N x ‐C) with different N coordination numbers have been fabricated by controlling the pyrolysis temperature. Significantly, the Ni SA ‐N 2 ‐C catalyst, with the lowest N coordination number, achieves high CO Faradaic efficiency (98 %) and turnover frequency (1622 h −1 ), far superior to those of Ni SA ‐N 3 ‐C and Ni SA ‐N 4 ‐C, in electrocatalytic CO 2 reduction. Theoretical calculations reveal that the low N coordination number of single‐atom Ni sites in Ni SA ‐N 2 ‐C is favorable to the formation of COOH* intermediate and thus accounts for its superior activity.