Electron transport by intramolecular cascaded π-conjugation channels of D-A two-dimensional conjugated microporous polymer mediate photo-induced RCMP

Abstract

The photo-induced reversible complexation-mediated radical polymerization (photo-induced RCMP) has the feature of energy-saving and environmentally friendly, which is compatible with the sustainable development advocated by the world. To promote the development of photo-induced RCMP, three two-dimensional conjugated microporous polymers (CMPs) based on different construction units were developed by aldehyde-ammonia condensation and used as catalysts, producing polymethacrylates with precise molecular weight and narrow molecular weight dispersion. Chain extension, monomer compatibility and spatiotemporal control experiments revealed the high chain end fidelity of obtain polymethacrylates and the universality of photo-RCMP process by using synthetic CMPs catalysts. The density functional theory (DFT) calculation reveals that all the highest unoccupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of three CMPs are in junction segment and connecting segment respectively, which exhibits strong electron distribution asymmetry. Moreover, the DFT and experimental results verified that the (donor-acceptor) D-A structure with push-pull electron ability and π-conjugated electron channel promote intermolecular charge transfer, which reduce the Gibbs free energy of photo-induced RCMP to increase the electron transport ability and the polymerization rate. This work indicates that by the construction of D-A structure and π-conjugated electron channel can effectively enhance the catalytic properties of CMPs-based photocatalysts, which provides a methodology to design heterogeneous photocatalysts for photo-induced RCMP.