Molecular Design\nof Two-Dimensional Antiaromatic Covalent\nOrganic Frameworks for Solar-Driven Overall Water Splitting

The search for metal-free photocatalysts capable of solar-driven\noverall water splitting is highly pursued but challenging. Modular\nsynthesis enables the creation of two-dimensional (2D) covalent organic\nframeworks that possess tunable electronic and optical properties,\nas well as abundant chemically active functional units that are useful\nfor photocatalysis. Therefore, we employed a molecular design strategy\nto create 22 antiaromatic 2D COFs by assembling dibenzopentalene (DBP)\nas linker and 21 molecules as nodes, resulting in four 2D topologies.\nWe studied their potential for solar-driven overall water splitting.\nThe results suggest that all of the 2D COFs exhibit a response to\nvisible light and possess band gaps ranging from 1.21 to 2.29 eV.\nParticularly, a 2D COF tessellated with DBP and 1,3,5-triazine (TRZN)\nmight facilitate the independent occurrence of the hydrogen and oxygen\nevolution reactions at distinct active sites under light irradiation.\nIn addition, the photocatalytic overall water splitting using solar\nenergy can be achieved in a 2D COF composed of benzene- and halogen-modified\nDBP due to the increased oxidation potential. Noteworthy, the solar\nto hydrogen (STH) efficiencies of the two systems are estimated to\nbe 15.8 and 12.6%, respectively. This study has showcased the capability\nof antiaromatic COFs in photocatalytic overall water splitting using\nsolar energy.