Acridinium-based photoredox nanocatalysts for site-selective arene C–H amination in water

The development of photoredox catalysis in water allows access to green and sustainable organic synthesis. Acridinium salts are entirely organic, powerful, inexpensive, and environmentally friendly photocatalysts, but most of them have poor solubility in aqueous media, leading to a lack of control over their sizes and morphologies that play an important role in catalytic performance. To tackle this challenge, here we have devised an effective strategy for the preparation of acridinium-based photoredox nanocatalysts with controllable size and morphologies in water by using mixing-induced nanoprecipitation (MINP). These catalytic systems could be utilized for site-selective arene C–H amination in water under open air. To inhibit the degradation of acridinium salts, 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) was incorporated for the enhancement of catalytic performance. Moreover, a TEMPO-containing polymer was synthesized for the co-immobilization of an acridinium salt and TEMPO to facilitate their recovery and reuse. As a proof-of-concept, this work may open up an avenue for the development of photoredox nanocatalysts with controllable size and morphologies and for their co-immobilization with other catalytic components.