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

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 gcat–1 h–1, outperforming that of NO2-TEE-POP (1609 μmol gcat–1 h–1). This work highlights the pivotal role of microenvironmental engineering of porous organic polymer photocatalysts for achieving efficient H2O2 production.