Regulating the activity of intrinsic sites in covalent organic frameworks by introducing electro-withdrawing groups towards highly selective H2O2 electrosynthesis

Oxidized carbon catalysts have shown the potential of producing H2O2 electrochemically, and the seeking of a champion active site is usually the primary concern. However, preparing an optimal catalyst requires more activation factors rather than identifying the only oxygen-containing group that activates the adjacent carbon atoms. In this work, we treat the commonly studied oxygenated groups as the main activation factor and introduce groups with varied electron-withdrawing abilities into the system additionally, attempting to break the catalytic limit imposed by a single factor. In detail, we designed dioxin-linked covalent organic frameworks (COFs) in which each structural unit contains four C-O-C groups as the main activation factor and two more functional groups (-CN,-COOH, or -CH2OH) as the additional regulation factors. The active carbon atoms are located between these chemical groups and thus their catalytic activities are impacted by them simultaneously. Results show that the catalytic activity is positively associated with the electron -withdrawing ability of the additional groups. The well-tailored COF-CN achieved an ultrahigh H2O2 se-lectivity of 97.2% and an outstanding H2O2 yield of 901 mmol g-1 h-1, allowing it to be directly used for wood pulping and waste paper recycling without extra separation processes. Further calculations and ex-tended modeling of a nitrogen-dopant system suggest the universal potential of such an additional chemical influence design to go beyond the current electrocatalytic limit.(c) 2023 Elsevier Ltd. All rights reserved.

Automated summary

In this study, researchers introduced chemical groups with different electron-withdrawing abilities into oxidized carbon catalysts as additional regulation factors, aiming to break the catalytic limit. Results showed that the catalytic activity was positively associated with the electron-withdrawing ability of the additional groups. The well-tailored COF-CN achieved an ultrahigh H2O2 selectivity and yield, allowing it to be directly used for wood pulping and waste paper recycling. This additional chemical influence design has universal potential beyond the current electrocatalytic limit.