Microenvironmental modulation of triphenylamine-based and thiazolo[5,4-d]thiazole-linked conjugated porous organic polymers for enhanced photocatalytic C–H arylation performance

Abstract

Porous organic polymers (POPs) have emerged as a rapidly expanding class of photocatalytic materials owing to their unique structural and electronic attributes. Microenvironmental modulation of POPs offers an effective strategy for tuning their electronic properties and thereby regulating photocatalytic activity, enabling the development of high-performance photocatalysts. Herein, we evaluate the photocatalytic behavior of structurally modified triphenylamine-based and thiazolo[5,4-d]thiazole-linked conjugated POPs, in which O or S atoms are incorporated into the triphenylamine core. Experimental studies show that the microenvironmental modulation significantly regulates the band gaps, resulting in pronounced differences in their ability to catalyze the visible-light-driven C-H arylation of pyrroles with aryl halides, a benchmark reaction for assessing the photoredox efficiency. Among three POPs, POP2 containing an O-incorporated phenoxazine core exhibits the highest activity. Theoretical calculations further reveal that the O/S-incorporated POPs possess narrower band gaps than the pristine POP1. Moreover, in the POP2-mediated catalytic cycle, the key single-electron-transfer step from the photosensitizer radical anion to the aryl bromide shows the lowest activation barrier. Overall, this work demonstrates that rational structural regulation represents a promising strategy for developing high-performance POPs-based heterogeneous photocatalysts.