Abstract

Electrocatalytic water splitting is limited by the sluggish oxygen evolution reaction (OER). This study investigates how structural and electronic modifications in UiO-type zirconium metal-organic frameworks (MOFs) influence their catalytic activity toward the oxygen evolution reaction. UiO-67, constructed from biphenyl-4,4 ' dicarboxylate linkers, provides enlarged pore channels that enhance electrolyte accessibility and mass transport, whereas UiO-66-NO2, based on nitro-functionalized terephthalate linkers, incorporates strong electronwithdrawing groups that modulate the local Zr-O-C coordination environment. FE-SEM, FTIR, and N2 sorption analyses confirmed the characteristic fcu topology and high surface areas expected for successful linker incorporation. In 0.1 M KOH, UiO-67 exhibited an overpotential (eta 10) of 290 mV at 10 mA cm- 2, and a Tafel slope of 70 mV dec- 1. UiO-66-NO2 required 340 mV to reach 10 mA cm- 2, while commercial RuO2 showed an overpotential (eta 10) of 470 mV under identical conditions. Both MOFs sustained stable activity over 27 h of continuous electrolysis. These results demonstrate that integrating enlarged pore architectures with electronwithdrawing linker functionality can effectively reduce OER overpotentials and enhance charge-transfer characteristics in alkaline media.