Linker engineering in covalent organic polymers for enhanced electrocatalytic carbon dioxide reduction

Covalent organic polymers (COPs) are promising platforms for electrocatalytic carbon dioxide reduction reaction (CO₂RR) due to their tunable structures and designable functionality. Among the various structural parameters of COPs, the molecular configuration of linkers plays a critical role in determining catalytic activity. However, studies −−linker isomerism to modulate the physicochemical properties and catalytic behavior of COPs remain limited. Herein, we reported a linker isomerism strategy to tailor the electronic structure and CO₂RR performance of COP-based electrocatalysts. Specifically, COP-o, constructed from 1,10-phenanthroline-2,9-dicarbaldehyde (with ortho-positioned aldehyde groups), exhibited a more favorable cobalt electronic environment and accelerated electron transfer compared to its para-isomeric counterpart, COP-p, derived from 1,10-phenanthroline-4,7-dicarbaldehyde. Theoretical calculations further revealed that COP-o facilitated *COOH adsorption and CO desorption. Consequently, COP-o achieved a CO Faraday efficiency of 98 % and a partial CO current density of −12.28 mA cm⁻² at −0.76 V (vs. RHE). This work underscores the pivotal role of linker isomerism in modulating the metal coordination environment and electron transfer within the COP frameworks, offering valuable insights for the rational design of highly efficient CO₂RR electrocatalysts.