Abstract
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 π-conjugated coordination chemistry, we have developed several conductive MOFs as active oxygen reduction (ORR) electro catalysts 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-hexahydroxytriphenylene (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) · 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 n-conjugated metal-ligand Cu-O-C centers of Cu-HHTP MOF via shrinking the first Cu-O coordination sphere, realizing fast 2e~- ORR kinetics.
NSTL