Ionic Liquid-Based Colloidal Formulations for the Synthesis of Nano-MOFs: Applications in Gas Adsorption and Water Desalination

Microemulsions (MEs) comprising choline dioctyl-sulfosuccinate [Cho][AOT], a biobased ionic liquid (IL) surfactant as an emulsifier, (R)-(+)-limonene (RL) as a nonpolar phase, and ethylene glycol (EG)/ethanolammonium formate (EOAF) as an organic solvent/low-viscosity IL polar component were constructed. Spontaneous aggregation of [Cho][AOT] was observed with a negative Delta H form using isothermal titration calorimetry. The aggregates of [Cho][AOT] in RL showed a critical micellar concentration (cmc) of similar to 5.49 mM, EG (cmc similar to 3.99 mM), and EOAF (cmc similar to 1.56 mM), and these are further characterized by various techniques. These novel IL-based MEs have been used as nanoreactors for the sustainable synthesis of uniform nanosized metal-organic frameworks (N-MOFs), such as MIL-53(Al), HKUST-1, UIO-66-NH2, and ZIF-8, with a precise control over size and morphology at room temperature. Characterization of N-MOFs has been performed using scanning electron microscopy, powder X-ray diffraction, and Fourier transform infrared spectroscopy. The synthesized N-MOFs have been used to prepare stable and uniform thin film nanocomposite nanofiltration membranes, suitable for desalination of brackish water with excellent flux (31.8 LMH/bar) and rejection (99.0%) of divalent salts.

Automated summary

Microemulsions using biobased surfactant [Cho][AOT], nonpolar phase (R)-(+)-limonene, and organic solvent/low-viscosity IL polar component were utilized for sustainable synthesis of uniform nanosized metal-organic frameworks (N-MOFs). The N-MOFs were further characterized and used to prepare stable nanofiltration membranes for desalination of brackish water with high flux and rejection rates.