Optimisation of synthesis conditions for UiO-66-CO2H towards scale-up and its vapour sorption properties

Abstract

Based on the preferences of an industrial process for the production of MOFs we herein present a facile procedure for the synthesis of the zirconium based MOF UiO-66-CO₂H with the composition [Zr₆O₄(OH)₄(O₂C–C₄H₃CO₂H–CO₂)₆]·nH₂O. The synthesis utilises Zr(SO₄)₂·4H₂O and trimellitic acid (1,2,4-benzenetricarboxylic acid) in water as solvent. The product is already obtained after one hour under reflux with yields of 90% and extrapolated space–time yields up to 2000 kg m⁻³ d⁻¹ can be achieved. The reaction is carried out at ambient pressure which is particularly beneficial for the potential production of the MOF at industrial scale. The vapour sorption properties and stabilities of UiO-66-CO₂H were furthermore characterised in detail utilising methanol and water as fluids, respectively. While the harsh conditions for thermal water vapour cycling between 40 °C and 140 °C led to a rapid decline of sorption capacity, repeated cycling with methanol vapour did have a beneficial repairing effect on the framework's crystallinity.