Modulating Pore\nSizes and Electronic Properties of\nCovalent Organic Polymers for the Catalysis of Two-Electron Oxygen\nReduction Reaction in Neutral Media

Covalent organic polymers (COPs) have been used as electrocatalysts\nto produce hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) via a two-electron\noxygen reduction reaction (2e<sup>–</sup> ORR). However, performing\nthe 2e<sup>–</sup> ORR catalysis under neutral conditions remains\na challenge due to the lack of suitable catalytic sites and porosity.\nHerein, we adopted a modulating synthetic strategy to tailor the pore\nsizes and electronic properties and thus obtained a highly selective\nand active COP catalyst for the 2e<sup>–</sup> ORR in a neutral\nmedium. By modifying the linkers, the pore size of the COPs ranged\nfrom 0.49 to 0.87 nm, and the electronic state of the Cr centers also\nchanged. Cr-TCNE-COP, a COP with tetracyanoethylene linkers, showed\nhigh H<sub>2</sub>O<sub>2</sub> selectivity (95.3%) with a mass activity\nof 398.2 A g<sup>–1</sup> at a potential of 0 V vs RHE, which\nwas 1.6 times higher than that of the COP with pyromellitic dianhydride\nlinkers, Cr-PMDA-COP. The results indicate that a shorter carbon matrix\nadjacent to the Cr active sites favored the adsorption of O<sub>2</sub> and desorption of *OOH. This study opens the road for efficient\nH<sub>2</sub>O<sub>2</sub> electroproduction in neutral media by synergistically\nmanipulating the reaction pore microenvironment and electronic state.