A Simple Molecular Design Strategy for Two-Dimensional Covalent Organic Framework capable of Visible-Light-Driven Water Splitting

Two-dimensional (2D) covalent organic frameworks (COFs) are promising metal-free materials for photocatalytic water splitting because of their high surface area and predictability to assemble various molecule with tunable electronic prop-erties. Unfortunately, 2D COFs capable of visible-light-driven photocatalytic overall water splitting are rare partly due to rigorous requirements to their band alignments and coexistence of catalytic sites for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, twelve 2D nitrogen-linked COFs are designed based on first-principles calculations and topological assembly of molecular segments with catalytic activities toward either HER or OER, respectively. The electronic band structures calculated with HSE06 method indicate that 2D COFs are semiconduc-tors with widely tunable bandgap ranging from 1.92 to 3.23 eV. The position of both conduction and valence band edges of nine 2D COFs match well with the chemical reaction potential of H2/H+ and...