Fully Conjugated Microporous Polymers as Metal-Free Heterogeneous Photocatalysts for Organic Transformations

Photoactive conjugated microporous polymers (CMPs) have recently received huge attention in photocatalytic organic transformations owing to their adjustable structure and functionality. However, commonly reported CMPs are synthesized through metal catalyzed coupling reactions, which require complicated product separation and result in increased costs. In this study, two sp² carbon-linked CMPs are constructed by organic base induced Knoevenagel reaction using 2,6-dimethylbenzo[1,2-d:4,5-d']bisoxazole and aromatic polyaldehydes as co-monomers. The new benzobisoxazole-based polymer materials feature fully π-conjugated skeleton with broad visible-light absorption, permanent porosity as well as outstanding stability. Importantly, they can effectively induce many organic reactions such as C-3 thiocyanation of indoles under visible-light illumination and show broad substrate applicability and superior recyclability.