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

Abstract Porous heterostructured electrocatalysts with multifunctionality and synergistic effect have much benefit for efficient electrocatalytic CO₂ reduction reaction (CO₂RR), 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 CO₂RR. 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 (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.