Covalent Organic Frameworks with Molecularly Electronic Modulation as Metal-Free Electrocatalysts for Efficient Hydrogen Peroxide Production

Tuning the electronic property of active center to balance the adsorption ability and reactivity of oxygen is essential for achieving 2e(-) oxygen reduction reaction (ORR) for electrocatalytic synthesis of hydrogen peroxide (H2O2), which still represents a grand challenge. Herein, different by-design building blocks are introduced to regulate the electronic structure of catalytically active centers in covalent organic frameworks (COFs). Theoretical calculation reveals that adsorption ability of oxygen molecule (O-2) can be finely tuned by the regulation of electronic structure and the binding strength of O-2 is positively correlated with the electron donating ability of active center. As a result, the newly designed TP-TD-COF shows higher 2e(-) ORR activity and selectivity owing to the stronger electron donating ability and the higher adsorption strength of O-2 on electron-rich active center. This work reveals fundamental structure-activity relationship in H2O2 synthesis and offers a strategy for designing metal-free COF catalysts through rational modulation of their electronic properties at molecular level.

Automated summary

Tuning the electronic structure of the active centers in covalent organic frameworks (COFs) is crucial for balancing the adsorption ability and reactivity of oxygen in the 2e(-) oxygen reduction reaction (ORR) for electrocatalytic synthesis of hydrogen peroxide (H2O2). By introducing different by-design building blocks, the adsorption ability of oxygen molecule (O-2) can be finely tuned, and the binding strength of O-2 is positively correlated with the electron-donating ability of the active center. The newly designed TP-TD-COF exhibits higher 2e(-) ORR activity and selectivity due to its stronger electron-donating ability and higher adsorption strength of O-2 on the electron-rich active center. This work reveals the fundamental structure-activity relationship in H2O2 synthesis and provides a strategy for designing metal-free COF catalysts through rational modulation of their electronic properties at the molecular level.