Microenvironment Engineering in Pyridyl-Acetylene-Based Porous Organic Polymers for Enhanced H2O2 Photosynthesis

Abstract

Artificial photosynthesis of hydrogen peroxide (H₂O₂) from pure water and oxygen, without relying on sacrificial agents, offers a sustainable alternative to the conventional industrial anthraquinone method. Nevertheless, the insufficient proton (H⁺) supply derived from the sluggish water oxidation limits the overall photocatalytic H₂O₂ production rate. Herein, two pyridyl-acetylene-based porous organic polymers with identical skeletal structures but distinct substituents, namely, CH₃-TEE-POP and NO₂-TEE-POP, were synthesized by varying the substituent at the meta-position of the pyridinic nitrogen. The substituent at the meta-position of the pyridinic nitrogen influences the interaction between the pyridinic nitrogen and H₂O molecules. Density functional theory analysis reveals that the interaction between the N atom in the CH₃-TEE-POP skeleton and H₂O molecules is stronger than that in NO₂-TEE-POP, resulting in a more significant weakening of the O–H bond in water molecules. The weakening of the O–H bond facilitates the 4-electron water oxidation reaction to generate H⁺ and O₂ and simultaneously promotes the consumption of holes, leading to an improvement in the overall photocatalytic efficiency. Consequently, CH₃-TEE-POP achieves an exceptional initial H₂O₂ production rate of 3183 μmol g_cat^–1 h^–1, outperforming that of NO₂-TEE-POP (1609 μmol g_cat^–1 h^–1). This work highlights the pivotal role of microenvironmental engineering of porous organic polymer photocatalysts for achieving efficient H₂O₂ production.