Diversifying Single-Crystal Structures of Covalent Organic Polymers Through a Symmetry-Broken Strategy

Recently, growing single crystals of covalent organic polymers (COPs) through dative B←N bonds has been proven to be a promising strategy. Despite these developments, constructing diverse COP structures using identical structural motifs to investigate the variations in their performance remains a significant but challenging task. In this paper, we introduce a strategy aimed at reducing the symmetry of structural units to achieve this target. By employing the 3-pyridyl-based tetrathiafulvalene motif (labeled as TTF-(3-py)₄), a series of single-crystal COP structures sharing the same motifs, including one-dimensional (1D) zigzag chains (CityU-61), 1D nanobelt (CityU-62), and 2D layer (CityU-63) structures, are constructed under different solvent conditions. The rotatability of the carbon-carbon single bond, coupled with the deviation of nitrogen in pyridine from the symmetry axis, endows TTF-(3-py)₄ with a diverse range of configurations. These COP compounds exhibit excellent light absorption properties and redox activities, facilitating efficient photocatalytic synthesis of hydrogen peroxide (H₂O₂) from water and air. Notably, CityU-63 exhibits the highest catalytic activity, with an H₂O₂ production rate of 10 488.9 µmol g^-1 h^-1, positioning it among the most effective photocatalysts currently employed for H₂O₂ photosynthesis.