Covalent porous catalysts for electrochemical reduction of CO2

The electrocatalytic CO2 reduction reaction (eCO(2)RR) stands out as a highly promising approach to simultaneously resolving the issue of the elevated atmospheric CO2 concentration and its utilization to produce value-added products. One of the present challenges is the rational design of efficient catalysts toward the eCO(2)RR and the understanding of their structure-activity relationship. Covalent porous catalysts (CPCs) with atomically dispersed active sites embedded in the porous organic backbone, including polymer-based catalysts, such as covalent organic frameworks (COFs) and conjugated microporous polymers (CMPs), and molecule-based catalysts, such as porous organic cages (POCs) have received increasing attention recently. They feature extremely high atom utilization, customizable porosity, a customizable backbone, and distinct electronic properties. In this review, the design principles of CPCs, both in their selection of metal sites (metallic centers, heterometallic centers and their axial coordination) and optimization of organic backbones (chelating sites, their electronic modulation and microstructures) will be covered, aiming to provide guidance to tune their eCO(2)RR performance. Then representative examples will be discussed to reveal their structure-activity relationships. The perspective and key challenges in CPC based eCO(2)RR electrocatalysts will be finally proposed.