A recyclable type-I photosensitizer to enable red-light-driven gram-scale aerobic photocatalysis

Developing metal-free, purely organic photocatalysts with high recyclability and the ability to utilize red light to yield specific reactive oxygen species for aerobic photocatalysis is both crucial and challenging in current research. Herein, we first found that a type-I photosensitizer, EtNBS-H, can achieve red-light-driven aerobic photocatalysis with remarkable catalytic performance and facile recoverability. Upon irradiation with red light, EtNBS-H exclusively generates O₂ ^-•, enabling the efficient hydroxylation of arylboronic acids, and oxidization of thioethers and other substrates with conversion exceeding 99%. Significantly, EtNBS-H stands out for its simple recovery and reuse through a facile pH-tunable acid-base reaction. This allows for the attainment of high-purity products through extraction, and enables the retrieval of the photocatalyst from the reaction medium for subsequent reuse with an average recovery rate exceeding 94%. Moreover, utilizing EtNBS-H as a photocatalyst in the scale-up reaction, the gram-scale products with a yield of >95% and purity of >99% were obtained, highlighting its potential for the guidance of developing recyclable organic photocatalysts that harness red light. This work offers a promising approach for sustainable and large-scale photocatalytic organic synthesis.