Thiolation-Annulation-Assisted Synthesis of Fully Conjugated Benzothiophene-Linked Covalent Organic Framework toward Strongly Enhanced Photoelectrocatalytic Uranium Extraction
Yuxiang Zhao, Shengfei Li, Junyi Han, Guangen Fu, Lisha Liang, Mengwei Chen, Xu Wang, Tao Zhang
Abstract
Linear polythiophene materials have exhibited great potential in photo- and electrocatalysis due to their tunable electronic structures and excellent photoelectroactivity. Expanding the thiophene structure from a one-dimensional linear polymer to a two-dimensional covalent organic framework (2D COF) is expected to further enhance the light absorption/conversion efficiency. Here we show the synthesis of a fully conjugated 2D benzothiophene-linked COF (2DCOF-S) by the postmodification of a bromine-functionalized, vinyl-linked 2D COF (i.e., v-2DCOF-Br) through thiolation annulation. The high π conjugation largely extended the light absorption edge from 480 to 800 nm. Furthermore, an intrinsic donor–acceptor (D-A) structure between the benzothiophene and triazine cores was obtained, which significantly improves the separation capability of photogenerated electrons and holes. Finally, we demonstrate that the 2DCOF-S exhibited excellent performance in photoelectrocatalytic uranium extraction, in which the maximum saturated adsorption capacity of uranium is up to 643 mg g –1 within 2 h, which is superior to most COF-based extraction materials.