Efficient separation of methanol/dimethyl carbonate mixtures by UiO-66 MOF incorporated chitosan mixed-matrix membrane

Pervaporation shows great potential in separation of organic-organic mixtures that are widely involved in chemical and petrochemical industries, while the separation performance of polymeric membranes is undesirable for practical application. In this work, we incorporated UiO-66 (ZrCl₄) metal-organic frameworks (MOFs) into chitosan (CS) membrane to separate methanol-dimethyl carbonate (DMC) mixtures. ZrOCl₂·8H₂O or ZrCl₄ was selected as metal precursor to synthesize UiO-66, which aimed to investigate the structural defect of UiO-66 for the separation performance of mixed matrix membranes (MMMs). BET, ¹H NMR and low-angle XRD characterizations indicated that UiO-66 (ZrCl₄) with appropriate pore size is more suitable for preferentially permeate methanol over DMC. IR, dielectric relaxation and DSC characterizations combined with molecular simulations revealed the ideal interfacial morphology of UiO-66/CS MMMs was owing to the favorable molecular interactions including hydrogen bond interaction and van der Waals interaction. Pervaporation separation of methanol-DMC mixtures demonstrated that UiO-66 (ZrCl₄) nanofillers can simultaneously enhance the permeation flux and separation factor of CS membrane. The optimized 10 wt% UiO-66 (ZrCl₄)/CS MMM exhibited total flux and methanol/DMC separation factor of 355 g/m²h and 337 for 10 wt% methanol-DMC mixtures at 50 °C, which were 3.4-fold and 25-fold higher than that of the pure CS membrane, respectively, and outperformed the state-of-the-arts polymer-based membranes.