Thiophene-embedded conjugated microporous polymers for photocatalysis

Abstract

Various photoactive building blocks can be incorporated into porous organic polymers (POPs). The intrinsic properties, such as various synthetic methods, outstanding inherent porosity, easy tunability, rigid conjugated skeletons and high stability, endow the polymeric organic networks with wonderful potential to act as heterogeneous photocatalytic platforms. However, exploitation of efficient synthetic strategies for metal-free and nontoxic heterogenous photocatalysts, and further insights into the photocatalytic process in organic transformations are still necessary. In this context, we report the concise synthesis of two polymeric frameworks (BTP-CMP and TBTP-CMP) incorporated into bithiophene and thiophthene units via a “bottom-up” strategy. BTP-CMP and TBTP-CMP were employed as heterogeneous photocatalysts in the synthesis of benzimidazoles, and exhibited excellent catalytic activity (up to 98% yield, at least 15 iterative runs). Therefore, the thiophene-embedded networks can serve as stable efficient and recyclable heterogeneous photocatalysts. Additionally, based on the catalytic results of control experiments and the energy band structures of the materials and intermediates, a possible photocatalytic reaction mechanism has been proposed.