Reaction-Type-Dependent\nBehavior of Redox-Hopping\nin MOFsDoes Charge Transport Have a Preferred Direction?

Redox hopping is\nthe primary method of electron transport\nthrough\nredox-active metal–organic frameworks (MOFs). While redox hopping\nadequately supports the electrocatalytic application of MOFs, the\nfundamental understandings guiding the design of redox hopping MOFs\nremain nascent. In this study, we probe the rate of electron and hole\ntransport through a singular MOF scaffold to determine whether the\nproperties of the MOF promote the transport of one carrier over the\nother. A redox center, [Ru<sup>II</sup>(bpy)<sub>2</sub>(bpy-COOH)]<sup>2+</sup>, where bpy = 2,2′-bipyridine and bpy-COOH = 4-carboxy-2,2′-bipyridine,\nwas anchored within NU-1000. The electron hopping coefficients (<i>D</i><sub><i>e</i></sub>) and ion diffusion coefficients\n(<i>D</i><sub><i>i</i></sub>) were calculated\nvia chronoamperometry and application of the Scholz model. We found\nthat electrons transport more rapidly than holes in the studied MOF.\nInterestingly, the correlation between <i>D</i><sub><i>e</i></sub> and self-exchange rate built in previous research\npredicted reversely. The contradicting result indicates that spacing\nbetween the molecular moieties involved in a particular hopping process\ndominates the response.