Effect of Controllable Introduction of Hydroxyl Proportion in Covalent Triazine Polymers on Photocatalytic Performance

To address the insufficient understanding of how functional group loading affects the photocatalytic performance of covalent triazine polymers, three CTP-OH samples with different hydroxyl contents were synthesized via the superacid method by tuning the cyano molar ratio of the photoactive monomer 4,4'-(thiazolo5,4-dthiazole-2,5-diyl)dibenzonitrile to the hydroxyl-bearing monomer 4-(hydroxymethyl)benzonitrile (3∶1, 8∶1, and 18∶1). Photoelectrochemical characterization revealed that the sample CTP-OH-3-1 with the highest hydroxyl content (3∶1) exhibited the strongest photocurrent response and the lowest interfacial charge-transfer resistance. Under blue-light irradiation, the sample of CTP-OH-3-1 is capable of photocatalyzing the reaction of organic debromination with a yield of 67%, outperforming that of the 8∶1 (yield of 53%) and 18∶1 (yield of 50%) control samples. These results demonstrate that as the hydroxyl proportion increases, the light absorption, exciton dissociation, and charge transport capabilities of the CTP materials are simultaneously enhanced, thereby leading to improved photocatalytic efficiency. This work realizes the quantitative modulation of hydroxyl groups in CTP structures, elucidates the structure–activity relationship, and offers new insights for the design of conjugated polymer photocatalysts.