Tunable Nitrogen Defects on Graphitic Carbon Nitride toward the Visible-Light-Induced Reversible-Deactivation Radical Polymerization
Shiwei Han, Teng Qiu, Chongwen Xiong, Xiaoyu Li, Longhai Guo
Abstract
Introducing nitrogen defects has been confirmed to improve the photoactivity of graphitic carbon nitride, but this strategy is far from being employed in the field of photo-polymerization. Here, the nitrogen-deficient graphitic carbon nitride (g-C3Nx) is proposed as an effective photocatalyst for photoinduced electron/energy transfer reversible addition–fragmentation chain transfer (PET-RAFT) polymerization under visible light. The g-C3Nx was prepared through the thermal polymerization of melamine with the pre-treatment by using the different kinds of preparation tailoring agents (PTAs). It has been revealed that both the amount and the type of the PTA have a profound impact on the reaction rate and the induction period of this visible-light-driven PET-RAFT polymerization, attributed to modulating the optical absorption boundary and the carrier transport efficiency of g-C3Nx by the introduced defects of nitrogen vacancies and cyano groups. Under the optimal condition with 0.5 g of NaOH being employed as the PTA, a monomer conversion higher than 90% was obtained in the PET-RAFT polymerization, almost doubled in comparison to the conversion catalyzed by pristine g-C3N4 under the parallel 10 h of blue light (λmax = 465 nm) irradiation, and the induction period was also dramatically shortened. The as-synthesized polymers exhibit a kinetically controlled molecular weight with low dispersity (PDI < 1.2). Moreover, high end-group fidelity, universal monomer/chain transfer agent adaptation, and reliable reused capability are shown on the 2D sheets of g-C3Nx being applied as the potential semiconductor catalyst for PET-RAFT polymerization under visible light.