Reusable homogeneous metal- and additive-free photocatalyst for high-performance aerobic oxidation of alcohols to carboxylic acids

How to realize the recycling of homogeneous catalysts has been a great challenge for chemists. In this background, a new pyridinium compound was synthesized and applied in selective photocatalytic oxidation. This photocatalytic system is advantageous in accelerating the transformation of alcohols into acids by two consecutive routes, including (1) photocatalytic oxidation of alcohols to aldehydes; (2) photocatalytic oxidation and autoxidation of aldehydes to acids. By activating molecular oxygen into •O₂⁻ and ¹O₂, the system displays advantages of high efficiency and simplicity, as well as environment-friendly nature without metals or additives. Attractively, this compound as a homogeneous catalyst can be reused by direct filtration of products profiting from its high performance and stability. The present work develops a new approach to achieve an efficient and recyclable aerobic oxidation of alcohols into acids by using pyridinium-based photocatalysts and provides a valuable insight into the separation and recycling of homogeneous catalysts for economic compatibility and industrial application.