Piezocatalytic Performances of Conjugated Microporous Polymers with Donor-Acceptor Structures for Overall Water Splitting

Piezocatalytic overall water splitting (OWS) is a promising way to harvest hydrogen energy, but the search for efficient piezocatalysts is still challenging. The rational structure design for a piezocatalyst is one of the important strategies to improve the piezocatalytic performance. Inspired by 2D piezoelectric materials and the electron donor-acceptor (D-A) structure that can produce a built-in electric field to induce a charge pull-push effect, we target to explore the piezocatalytic properties of 2D conjugated microporous polymers (CMPs) with D-A structure for OWS. Herein, two D-A type CMPs with different D-A interactions, Zn-Salen-TEPT and Zn-Salen-TEPB, are rationally synthesized, and the piezocatalytic tests under ultrasonic irradiation show that they can efficiently catalyze OWS into H-2 and H2O2, with the H-2 yield rates of 3260.2 for Zn-Salen-TEPT and 1816.7 mu mol g(-1) h(-1) for Zn-Salen-TEPB. Experimental results and theoretical calculations show that the strong D-A interactions can effectively construct the built-in electric field which enhances the separation and migration of intrinsic charge carriers for the catalyst and improves the piezoelectric properties of CMPs. The stronger D-A interaction in Zn-Salen-TEPT results in the higher yield rates of H-2 relative to Zn-Salen-TEPB. The high sensitivity of these piezocatalysts to mechanical forces and their piezocatalytic performance for the OWS are also attributed to the combined effect of their large specific surface area, intrinsic dipoles, high flexibility, and abundant active sites. Thus, exploring the effect of the D-A structure on the piezoelectric properties of CMPs is a meaningful attempt to present a high economic value process for generating H-2 and H2O2 directly from pure water.