Strategically significant synthesis of conjugated porous organic polymers via retro diazotization chemistry

To overcome the limitations of conventional conjugated porous organic polymer (CPOP) syntheses that require harsh conditions or metal catalysts and fail to introduce halogen substituents such as –Br and –I in a controlled manner, we present herein a strategically significant synthesis method based on bismuthene-catalyzed photoredox C–H arylation via in situ diazotization. This approach provides enhanced polymer chain growth with relatively high Mw (up to 322 kDa), ideal poly-dispersity, tunable optical properties (visible to NIR region), and enabling to access to a broad range of monomers with high tolerance for halogens. To gain deeper insight into the mechanism of C–C bond formation via bismuthene-catalyzed photoredox C–H arylation, control and scavenger experiments were performed. The results confirm that CPOP growth proceeds through a single-electron transfer pathway, forming linear or cross-linked networks. The resulting polymers exhibited efficient photocatalytic activity for the selective oxidation of styrene to benzaldehyde via singlet oxygen as the dominant reactive species, achieving > 99% conversion and selectivity under blue LED irradiation. Remarkably, halogen-containing CPOPs (–Br, –I) afforded higher yields and superior photocatalytic efficiency, attributed to the heavy-atom effect and defect generation, which collectively enhance visible-light absorption and charge separation. Introducing halogen substituents into porous organic polymers usually requires harsh conditions or metal catalysis. Here, the authors show a photoredox C–H arylation via in situ diazotization which enables the synthesis of conjugated porous organic polymer with a broad range of monomers and tunable optical properties.