Flexible and robust bimetallic covalent organic frameworks for the reversible switching of electrocatalytic oxygen evolution activity

Flexible and robust catalysts present a highly intriguing issue owing to their unique dynamic and reversible switching nature, which can provide a solution to maximize the atom utilization efficiency. Herein, a convenient and efficient cation-exchange strategy was developed to prepare flexible and robust Co/V-incorporated bimetallic COF electrocatalysts (namely, CoxV1-x@COF-SO3) for the oxygen evolution reaction (OER). As expected, in a 1.0 M KOH electrolyte, the optimized bimetallic Co0.5V0.5@COF-SO3 showed high turnover frequency (TOF) (0.098 s(-1)) at the overpotential of 300 mV, which was superior to that of most of the recently reported excellent Co-based OER electrocatalysts, exhibiting high atom utilization efficiency. Most importantly, the flexible nature of Co0.5V0.5@COF-SO3 was also observed. After treatment with hydrochloric acid, the reformation of the catalysis-inert phase of COF-SO3H was observed. This unique transformation from the catalysis-active phase of Co0.5V0.5@COF-SO3 to the catalysis-inert phase of COF-SO3H can be repeated, suggesting reversible switching of OER activity, which are almost impossible to achieve in conventional catalysts. This work provides a new concept for the fundamental design of catalysts with reversible switching properties to improve the atom utilization efficiency and simplify the procedures of catalyst regeneration.