Distal Synergistic Effect in Bimetal-Organic Framework for Superior Catalytic Water Oxidation

Metal-organic frameworks (MOFs) are emerging as promising electro-catalysts for the oxygen evolution reaction (OER). The bimetallic design strategy was further adopted in MOFs to elevate the OER performance by a synergistic effect. The proximal metal-oxygen-metal bonding configuration with typical 3d(pi)-2p(pi)- 3d(pi) interaction was apparently essential for an effective electronic coupling between the metal centers. Here, we report an example of distal synergy in a bimetal-organic framework exhibiting a better OER activity than the monometallic counterparts, as well as the conventional proximal synergy. To achieve a current density of 10 mA<middle dot>cm(-2) , our electrodeposited bimetallic MOF, Co-Ni-(TCNQ)(2)(H2O)(2) (TCNQ = 7,7,8,8-tetracyanoquinodimethane), on a glassy-carbon electrode required an overpotential value of 220 mV. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations revealed distinctive electronic coupling between the Co(II)-3d(7) and Ni(II)-3d(8) centers, despite being 9 & Aring; apart, leading to an overall charge delocalization in the structure via TCNQ.