Ultrasound-assisted continuous aqueous synthesis of sulfonate, imidazolate, and carboxylate MOFs with high space time yield.

Abstract

The boom in metal-organic frameworks (MOFs) for applications from chemical separations and gas storage to membranes for energy conversion and storage has stimulated interest in scalable MOF production methods. Combining the increased heat and mass transfer of flow reactors with the enhanced mixing and nucleation rates of sono-chemical synthesis, we developed an ultrasound-assisted two-phase flow platform for the aqueous synthesis of MOFs spanning three ligand chemistries, sulfonate Ca-NDS (water), imidazolate ZIF-8, and carboxylate UiO-66-NH₂. We show that this reactor does not foul, facilitating continuous operation at an STY of 3.4 × 10⁴ (±1 × 10³) kg m^-3 day^-1 of proton-conducting Ca-NDS (water). ZIF-8 and UiO-66-NH₂ MOFs prepared in ultrasound-assisted flow with smaller, uniform particle sizes exhibited matched or superior gas sorption to those made in batch. These results highlight the potential of ultrasound-assisted flow synthesis for MOFs, offering enhanced nucleation alongside process intensification, and paving the way for more efficient MOF production.