A thienyl‐benzodithiophene‐based two‐dimensional conjugated covalent organic framework for fast photothermal conversion

Abstract Two‐dimensional conjugated covalent organic frameworks (2D c ‐COFs) are emerging semiconductor materials for optoelectronic and photothermal applications. In particular, the highly tailorable, semiconducting thiophene‐based 2D c ‐COFs have attracted considerable interest due to their nontrivial physicochemical properties such as photo‐activity, broad optical absorption, tunable electronic structures, and so forth. Herein, we demonstrate a novel, crystalline 2D c ‐COF based on thienyl‐functionalized benzodithiophene (BDT) and biphenyl (BP) via the Schiff‐base polycondensation reaction. The resultant BDT‐BP‐COF exhibits a broad optical absorption up to ca. 600 nm and decent π‐conjugation along the 2D polymer skeleton, as revealed by the optical absorption and theoretical calculations. The favorable π‐conjugation and the abundant electron‐rich thiophene units confer excellent photo‐activity to BDT‐BP‐COF towards the usage of solar energy. As a proof‐of‐concept application, we explore BDT‐BP‐COF in photothermal conversion, in which it shows a fast surface‐temperature increase upon light irradiation for seconds.