Ultrastable and Efficient Visible-Light-Driven Hydrogen Production Based on Donor-Acceptor Copolymerized Covalent Organic Polymer.

Abstract

Developing stable and efficient photocatalysts for H2 production under visible light is still a big challenge. In this work, a novel covalent organic polymer (COP)-based photocatalyst with trace ending groups was prepared by the efficient irreversible kinetic coupling reaction, i.e., nickel(0)-catalyzed Yamamoto-type Ullmann cross-coupling, using pyrene as electron donor and countpart, e.g., phenanthrolene, benzene, pyrazine, as electron acceptor. The newly developed optimal photocatalyst (termed as COP-TP3:1) has a 14-fold improvement in the H2 evolution rate from 3 to 42 μmol h-1 under visible light compared with the sample without donor-acceptor structure. Moreover, COP-TP3:1 also performs excellent photocatalytic activity under different water quality (deionized water, municipal water, commercial mineral water, and simulated seawater (NaCl 3 wt %)). Significantly, ignored decrease in H2 evolution can be observed after 20 hours cycling H2 production, and the performance is only reduced by about 7% even after discontinuous cycles of photocatalysis and storage for a month. The donor-acceptor units with trace ending groups contribute to suppress electron-holes recombination kinetics and the N coordination sites in electron-acceptors conduce to anchor Pt (as the cocatalyst) onto the surface of photocatalyst, both of which are conducive to the outstanding photocatalytic activity and stability. Accordingly, this work can provide guidance to design a stable and efficient photocatalyst by copolymerization for visible-light-driven H2 production.