Thiazolium-linked Crystalline Porous Covalent Organic Frameworks for Mixed Electronic-ionic Transport.

Developing efficiently mixed electronic-ionic (MEI) conductive pathways within a single functional material at the microscale is essential yet challenging for various electronic devices. Covalent organic frameworks (COFs) feature pre-designed functionalities and uniform pores, making them highly desirable platforms for the transport of electrons and ions. However, for MEI conductive COFs, achieving high crystallinity when incorporating high-density ionic groups within the extensively π-electron delocalized skeletons remains a challenge due to intermolecular interactions. Herein, we reported a "pre-polymerization followed by self-ionization" approach to synthesize new thiazolium-linked COFs (MEICOFs, M = Cu, Co, Fe), where the ionic groups synthesized following the connection of building blocks. These MEICOFs demonstrated broad ultraviolet-visible-near-infrared absorption bands and narrow band gaps. As a proof of concept, the mixed electronic and hydroxide ionic conductivity of CuEICOF were determined to be 55.2 and 0.01 S m-1, respectively. Moreover, MEICOFs film could directly catalyze the oxygen reduction reaction without additional conductive agent and the rotation of electrode.