Modulating Band Structure and Cocatalyst Interactions in CTFs through Thiophene Linker Engineering for Superior Hydrogen Photoproduction

Covalent triazine frameworks (CTFs), characterized by the presence of pyridine nitrogen in their triazine units, show great promise for photocatalytic hydrogen evolution (PHE) reactions. In this work, two thiophene-bridged CTFs are designed and synthesized, TA-BD and TA-TD, using 2,2′-bithiophene (BT) and thieno[3,2-b]thiophene (TT) unit, respectively, as the π-conjugated linkers. These frameworks were prepared via a condensation reaction between the respective dialdehydes and p-phenylene terephthalamide. Among the CTFs, TA-BD exhibited a significantly higher hydrogen evolution rate (HER) of 9.14 μmol h–1 (10 mg of catalyst), which is 6.3 times greater than that of TA-TD (1.45 μmol h–1). Further investigation of the photoelectric properties revealed that the incorporation of a BT linker in TA-BD, compared to TT in TA-TD, results in a stronger thermodynamic driving force and improved charge separation and transfer. Upon photodeposition of Pd nanoparticles (NPs) onto the CTFs, the resulting nanocomposites demonstrated dramatically enhanced PHE activity. Under identical conditions, 10 mg Pd@TA-BD (3 wt %) achieved a HER rate of 76.16 μmol h–1, 8.3 times higher than that of bare TA-BD and approximately 4.3 times higher than that of Pd@TA-TD (3 wt %).