Rational Design of Donor-Acceptor Conjugated Microporous Polymers for Visible Light-Driven Oxidative C─N and C─S Bond Formation Reactions.

Abstract

Metal-free, visible-light-responsive heterogeneous organic photocatalysts have recently attracted significant attention over traditional metal-based systems. Herein, we report the design and synthesis of three conjugated microporous polymers (CMP) derived from 1,3,5-tris(diphenylamino)benzene (TDPAB) via an acid-catalyzed polymerization strategy, affording highly robust and porous frameworks. Among three materials, TDPAB-FC exhibits highest Brunauer-Emmett-Teller (BET) surface area of 545 m2  g-1, which facilitates efficient substrate diffusion and exposure of active sites; subsequently, TDPAB-FC is further used as the optimized catalyst for the photocatalytic oxidative coupling reactions. Transmission electron microscopy (TEM) analysis reveals a well-defined hollow rod-like morphology. The CMP possesses an intrinsic donor-acceptor architecture, enabling effective separation of photogenerated charge carriers under blue-light irradiation. Notably, the conduction band position is determined to be -0.463 V, which is thermodynamically favorable for the molecular oxygen reduction to generate reactive oxygen species (ROS). These combined structural and electronic features significantly enhance photocatalytic efficiency. They demonstrated excellent photocatalytic rate of 29.7 mmol g-1 h-1 and high mass-specific activity of 148.5 mmol g-1, for sustainable organic transformation, including benzylamine coupling reactions (yield up to 99%), sulfide oxidation (yield up to 99%), and thiocyanation of indoles (C-S coupling) (yield up to 99%), under mild conditions. Further, they exhibit outstanding recyclability over multiple catalytic cycles.