A Honeycomb‐Like Porous Crystalline Hetero‐Electrocatalyst for Efficient Electrocatalytic CO2 Reduction

Porous heterostructured electrocatalysts with multifunctionality and synergistic effect have much benefit for efficient electrocatalytic CO2 reduction reaction (CO2 RR), yet it still remains a daunting challenge to explore heterostructures based on covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) in this field. Here, a series of honeycomb-like porous crystalline hetero-electrocatalysts (MCH-X, X = 1-4, X stands for the numbered sample obtained from different MOF doses in the synthesis of the MCH) are synthesized, and these are successfully applied in electrocatalytic CO2 RR. The specially designed heterostructures with integrated porous MOF-template and ultrathin COF-coating enable efficient CO2 adsorption/activation and conversion into CH4 . The best of them, MCH-3, shows greatly inhibited H2 evolution, excellent current density (-398.1 mA cm-2 ), and superior FECH4${\rm{F}}{{\rm{E}}_{{\rm{C}}{{\rm{H}}_4}}}$ (76.7%) to the physical mixture (38.0%), the MOF@COF without the honeycomb-like morphology (47.7%), and the bare COF (37.5%) and MOF (15.9%) at -1.0 V. Based on the density functional theory calculations and various characterizations, the vital roles of the MOF in facilitating CO2 adsorption/activation, stabilizing intermediates, and conquering the energy barrier of rate-determining step are intensively studied.