Thiolation-Annulation-Assisted Synthesis of Fully Conjugated Benzothiophene-Linked Covalent Organic Framework toward Strongly Enhanced Photoelectrocatalytic Uranium Extraction

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.