Schiff-Base Hybrid Porous Polymers as Additive-Free Photocatalysts for Efficient Photodegradation of Dyes and...

The design and synthesis of photocatalysts with high activity, stability, and visible-light responsiveness remains a significant challenge in catalyst development. In this study, Schiff-base hybrid cross-linked porous polymers (TFBE-SHCP) were prepared through aldehyde-amine condensation reactions using octakis(4-aminophenyl)silsesquioxane (OAPS) as the building block and tetrakis[4-formyl-(1,1'-biphenyl)-4-yl]ethylene (TFBE) as the electron-donating linker. The introduction of TFBE monomers featuring a π-conjugated structure not only extends the light absorption into the visible-light region but also enhances the separation efficiency of photogenerated charge carriers. The porous structure of TFBE-SHCP further increases the number of catalytic active sites, significantly improving its photodegradation capability for water pollutants. Under visible-light irradiation, the polymer exhibits degradation efficiencies of 98% (3 min), 98% (30 min), and 72% (8 min) toward Congo red (CR), Rhodamine B (RB), and tetracycline hydrochloride (TH), respectively, when the degradation equilibrium is reached (20 ppm pollutant, additive-free). The corresponding apparent rate constants are 1.40, 0.07, and 0.19 min^-1, which are 2.1-11.4 times higher than those of recently reported photocatalysts. Our findings reveal that the conjugated structure of TFBE, together with the extended π delocalization within the three-dimensional porous framework formed via C═N cross-linking, effectively promotes the separation of photogenerated electron-hole pairs, thereby enhancing the photocatalytic activity. This work provides fundamental insights into modulating delocalized π electrons to improve the photocatalytic performance.