Quasi-One-Dimensional\nZigzag Covalent Organic Frameworks\nfor Photocatalytic Hydrogen\nEvolution from Water

Abstract

Covalent\norganic frameworks (COFs) have potential applications\nin a wide range of fields. However, it remains a critical challenge\nto constrain their covalent expansions in the one-dimensional (1D)\ndirection. Here, we developed a general approach to fabricate 15 different\nhighly crystalline COFs with zigzag-packed 1D porous organic chains\nthrough the condensation of V-shaped ditopic linkers and X-shaped\ntetratopic knots. Appropriate geometrical combinations of a wide scope\nof linkers and knots with distinct aromatic cores, linkages, and functionalities\noffer a series of quasi-1D COFs with dominant pore sizes of 7–13\nÅ and surface areas of 116–784 m² g^–1. Among them, nitrogen (N)-doped 1D COFs with site-specific doping\nof heteroatoms favor a tunable control of band structures and conjugations\nand thus allow a remarkable hydrogen evolution rate up to 80 mmol\ng^–1 h^–1 in photocatalytic water\nsplitting. This general strategy toward programming function in porous\ncrystalline materials has the potential to tune the topologically\nwell-defined electronic properties through precisely periodic doping.