Phenylene Spacer Incorporation Enables Band Structure Engineering of 2D Heterotriangulene Polymers for Enhanced Photocatalytic Hydrogen Evolution

Direct H2 evolution via photocatalytic water splitting is the most green and sustainable way to facilitate hydrogen economy. Strategies to achieve metal-free and efficient photocatalysts are crucial for the wide application of this technology. Herein, a kind of novel two-dimensional (2D) polymers, namely, 2D heterotriangulene-phenylenes (HT-phenylenes), are designed and investigated as metal-free photocatalysts for hydrogen evolution by means of systematic first-principles calculations. We demonstrate that phenylene incorporation is an efficient strategy to tune the electronic and optical properties of 2D polymers for photocatalysis. The designed 2D HT-phenylenes show moderate band gaps, pronounced optical absorption, and high carrier mobility to facilitate photocatalytic H2 evolution. Remarkably, the incorporation of 1,4-phenylene spacers allows dynamically tunable photocatalytic activity due to the flexible C–C single bond, and the spacer rotation increases the driving potential for the hydrogen evolution reaction.