Similar coordination environments promote indium-doped MOF-74-Co precatalysts for oxygen evolution reaction

The sluggish kinetics of the oxygen evolution reaction (OER) necessitate the use of efficient, non-precious metal catalysts. This work reports the rational design of an indium-doped bimetallic metal-organic framework (MOF-74-CoIn) as a precatalyst, achieved through post-synthetic modification of MOF-74-Co. Structural and spectroscopic analyses confirm that In(III) incorporation induces CoO bond contraction while preserves the overall structural integrity. After the complete electrochemical activation, MOF-74-CoIn-OER exhibits exceptional OER performance in 1.0 M KOH solution, achieving a low overpotential of 308 mV at 10 mA cm^-2, a reduced Tafel slope (58.1 mV dec^-1), and high stability (95.2 % current retention after 120 h). A series of physicochemical characterizations reveal that In(III) doping accelerates the electrochemical reconstruction into an amorphous but active In-doped CoOOH phase, with In stabilizing Co³⁺ sites and facilitating rapid phase transformation. Furthermore, theoretical calculations confirm that In incorporation effectively lowers the energy barrier of In-O-Co electronic bridge for OER by altering the density of states of CoOOH. This study demonstrates the critical role of indium as an electronic modulator, offering atomic-level insights into dynamic activation of MOF precatalysts for efficient water oxidation.