Electrocatalytic CO₂ Reduction: from Discrete Molecular Catalysts to Their Integrated Catalytic Materials

Molecular catalysts (metal complexes), with molecularly defined uniform active sites and atomically precise structural tailorability allowing for regulating catalytic performance through metal- and ligand-centered engineering and elucidating reaction mechanisms via routine photoelectrochemical characterizations, have been increasingly explored for electrocatalytic CO₂ reduction (ECR). However, their poor stability and low catalytic current density are undesirable for practical applications. Heterogenizing discrete molecular catalysts can potentially surmount these issues, and the resulting integrated catalysts largely share catalytical properties with their discrete molecular counterparts, which bridge the gap between heterogeneous and homogeneous catalysis and combine their advantages. This minireview surveys advances in design and regulation of molecular catalysts such as porphyrin, phthalocyanine, and bipyridine-based metal complexes and their integrated catalytic materials for selective ECR.