Dissecting π-conjugated covalent-coupling over conductive MOFs toward efficient two-electron oxygen reduction

The metal-ligand (M-L) covalent coupling is of very significance for tailoring the activity and selectivity of metal -organic-framework (MOF) functional nanomaterials, yet it still remains elusive. Herein, based on the ??-conju-gated coordination chemistry, we have developed several conductive MOFs as active oxygen reduction (ORR) electrocatalysts with tunable H2O2 selectivity. Through tailoring the central metal and the first coordination sphere, weakly-electrophilic Cu sites coupled with strongly-oxidized aromatic 2, 3, 6, 7, 10, 11-hexahydroxytri-phenylene (HHTP) linkers are of high favor in a two-electron ORR pathway, resulting in an impressive H2O2 selectivity of 95 % and a superior H2O2 yield rate of 792.7 mmol.g(cat)(-1)1.h(-1) during ORR for conductive Cu-HHTP MOF catalysts. By correlative in situ synchrotron radiation XAFS and FTIR spectroscopies, the potential -dependent dynamic-coupling hydroxyl over Cu sites is found to effectively trigger the self-polarization of ??-conjugated metal-ligand Cu-O-C centers of Cu-HHTP MOF via shrinking the first Cu-O coordination sphere, realizing fast 2e(-) ORR kinetics.