Tuning the Bifunctional Electrocatalytic Activity of UiO‐66‐NH ₂ for Overall Water Splitting Through Carboxylate Modulation Using ZrOCl ₂ ·8H ₂ O

ABSTRACT The drive toward efficient hydrogen technologies demands electrocatalysts that unite low cost with strong bifunctional activity. Here, we explore a microwave‐assisted route to UiO‐66‐NH 2 using ZrOCl 2 ·8H 2 O, where the coordinated water molecules within the precursor unexpectedly act as structural contributors, steering crystal development and enhancing both hydrogen and oxygen evolution performances. Carboxylate modulation with acetic, formic, and benzoic acids further reshapes the physicochemical landscape of the MOFs, inducing controlled variations in nanoparticle dimensions, electronic structure, and surface defect environments. These modulators not only tune the bandgap but also influence the oxidation states revealed in X‐ray photoelectron spectra, directly impacting charge‐transfer characteristics. Among the explored systems, acetic acid modulation promotes an optimal interplay between defect density and conductive pathways, yielding highly stable and responsive catalytic interfaces suitable for overall water splitting. This study reveals how precursor‐bound water, rational modulator choice, and rapid microwave crystallization synergistically govern the electrocatalytic identity of UiO‐66‐NH 2 . The findings emphasize the broader potential of strategic defect engineering, accessible zirconium sources, and sustainable synthesis routes in developing next‐generation MOF‐based catalysts for clean energy applications.