Green ionic metal-organic frameworks as nanocatalysts for CO₂ fixation

Co, Ni, and Zn iso-reticular coordination polymers of 2,5-dihydroxyterphthalic acid (H₂dot) can be rapidly obtained under room temperature and aqueous conditions using either sodium or ammonium hydroxide as the bases to deprotonate the linker. The use of metal bromides and tetrabutylammonium hydroxide (TBAOH) as the base allows the green synthesis of ionic metal-organic frameworks (MOFs), characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), H-nuclear magnetic resonance (NMR), elemental analysis, and X-ray photoelectron spectroscopy (XPS), and employed in the pressure, solvent, and additive-free CO₂ fixation to epoxides by its cycloaddition to epichlorohydrin, exhibiting a cooperative behavior between the MOF and the ionic liquid formed within the framework, achieving TONs of the confined tetrabutylammonium bromide (TBABr) up to 700.