Hydroxyl-groups engineering of triazole-based polymers for efficient photocatalytic hydrogen peroxide production

Photocatalytic hydrogen peroxide (H2O2) production via indirect two-electrons oxygen reduction reaction (indirect 2e(-) ORR) is severely limited by the unsatisfactory O-2/H+ mass transfer and slow interfacial charge transfer efficiency. Herein, side-engineered triazole-based polymers (TZPs) are reported for efficient photocatalytic H2O2 production without sacrificial agent. The photoelectric properties, mass transfer and photocatalytic activities can be tuned by the distribution of hydroxyl groups on the benzenetricarboxaldehyde ring of TZPs. Theoretical calculations reveal that the asymmetric 2-hydroxyl-1,3,5-benzenetricarboxaldehyde monomer renders TZP-OE the largest dipole moment (2.5814 Debya) and the lowest first excited state index (3.654 eV). Moreover, the hydroxyl group optimizes the H2O wettability of TZPs. Benefiting from the enlarged intermolecular polarization-induced built-in electric field and excellent hydrophilicity, TZP-OE exhibits excellent photocatalytic H2O2 evolution rate of 1618 mu mol/L under visible light irradiation, which is 3.5 times that of TZP-NE. Therefore, side-group engineering provides a new approach for the regulation of catalyst structure and photocatalytic activity.