Unhomologous Modulation with Benzoic Acid Directs the Crystal Habits of ZIF-67 for CO ₂ Cycloaddition Catalysis

This study introduces benzoic acid (BA) as an unhomologous, O-donor modulator for the morphological engineering of the N-donor ZIF-67 framework. By systematically varying BA and linker concentrations, tunable crystal sizes (500–4000 nm) and distinct habit transitions were achieved while preserving the underlying sodalite topology. UV–vis spectroscopy, DFT calculations, and molecular dynamics (MD) simulations reveal that benzoate competitively coordinates to Co 2+ sites, regulating nucleation kinetics despite the chemical antagonism between carboxylate and imidazolate species. These structural modifications were tested for performance in the cycloaddition of CO 2 using epichlorohydrin, with the optimized catalyst exhibiting high conversion of CO 2 . This work establishes a robust structure–property relationship for modulator-directed MOF synthesis, demonstrating that nonconventional modulators are alternative tools for tailoring material functionality in carbon utilization.