Rapid Flow Synthesis of Zr-MOF Nanoparticles in Supercritical CO2 for Toxic Chemical Removal.

Abstract

Zirconium-based metal-organic frameworks (Zr-MOFs) are promising materials for the adsorption and degradation of toxic chemicals; however, their scalable synthesis is hindered by the slow formation of Zr-oxo clusters. Here, we report rapid flow synthesis of Zr-MOF nanoparticles in supercritical carbon dioxide (scCO2). Using UiO-66 as a model system, we observe fast particle formation (17 s) and achieve 54% ± 0.28% yield in 75 s with an averaged BET surface area of 1274 ± 38 m2g-1. Possible contributing factors to the fast nucleation include reduced solvent polarity, fast mass transfer, and modulated solute miscibility with the scCO2/DMF medium. Acid modulators appear to be critical for regulating Zr-oxo cluster formation and the morphological transition from nanoparticle aggregates to single crystals. This strategy is extended to the synthesis of high-quality UiO-66-NH2 and MOF-808. Products of the rapidly synthesized UiO series were evaluated for chemical warfare agent (CWA) simulant decomposition and TICs adsorption. UiO-66-NH2 showed faster DMNP hydrolysis and higher NH3, Cl2, and CK uptake than UiO-66, with performance comparable to MOFs produced by days-long batch synthesis.