Energy Level Engineering of Dihydrophenazine-Based Covalent Organic Frameworks Through π-Expansion of Cores Toward Tandem Photocatalytic Polymerization.

Covalent organic frameworks (COFs) incorporating photoredox-active motifs show great promise as heterogeneous catalysts, yet their applications have been largely confined to one-step transformations. In this work, we design and synthesize a series of three-dimensional (3D) COFs with different π-extended dihydrophenazine cores to achieve superior photocatalytic performance. These 3D COFs exhibit excellent crystallinity, high surface areas, and remarkable chemical stability. More importantly, they can work as highly efficient and recyclable catalysts for photocatalytic tandem polymerization reactions using styrene and fluoroalkyl anhydrides as substrates, yielding fluoroalkylated polystyrene polymers with narrow dispersity. These COFs constitute the first examples as tandem photocatalysts toward polymerization reactions. Moreover, optimal energy level alignment and enhanced photophysical properties are identified as key factors contributing to their high efficacy. This work not only provides a viable design strategy for multifunctional COF catalysts, but also expands their utility in complex synthetic sequences involving tandem catalytic processes.