Electrocatalytic acetylene semihydrogenation triggered by double exchange interaction over heteronuclear metal-organic framework.

Heteronuclear metal-organic frameworks (MOF) possesses the different polyhedral structural units readily trigger the unique double-exchange interaction (DEI), which is anticipated to activate inert CC triple bond and further enhance the electrocatalytic acetylene semihydrogenation activity. Herein, a novel BTC-Co-O-Cu-BTA (BTC = benzene-1,3,5-tricarboxylic acid; BTA = 1,2,4,5 benzene tetraamine) MOF is designed that realized a remarkably ameliorative ethylene partial current density of -149.4 mA cm-2 and a large ethylene Faradaic efficiency of 91.1 % at -0.8 V vs. RHE compared with the pristine homonuclear MOF. Systematic characterizations corroborate that the DEI handily transforms static Co3+-O-Cu2+ to vibronic double-exchange of Co2+-O-Cu3+ with the eg2 and eg0 electron filling state of Co and Cu sites, respectively. Subsequently, the lone-pair electron of eg orbital initially donate to the π⁎ antibonding orbital of acetylene molecule, thereafter the generated empty eg orbital accept the acetylene π orbital electron, guaranteeing the effective activation of acetylene to ethylene on the precisely devised heteronuclear MOF.