Effect of ZIF-71 ligand-exchange surface modification on biofuel recovery through pervaporation

In this paper, zeolitic imidazolate framework-71 (ZIF-71) particles (~500 nm diameter) were modified with four different ligands through the solvent-assisted linker exchange (SALE) method. The objective of this was to assess the effect of ligand exchanged ZIF-71 on the performance of ZIF-71/polydimethylsiloxane (PDMS) mixed matrix membranes (MMMs) for removal of alcohol from dilute aqueous solutions. Both Fourier-transform infrared spectroscopy (ATR-FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopy confirmed the exchange of the new ligands into the ZIF-71 material. The 1H NMR spectra demonstrated the molar ratios of the ligand-exchange into the ZIF-71 particles. X-ray diffraction and scanning electron microscopy results showed that the crystal structure and the morphology of ZIF-71 were maintained after the ligand-exchange modification process. Modified ZIF-71/PDMS composite membranes were synthesized to study the effect of ligand modification on alcohol/water separation performance. Ligand-modified ZIFs dispersed more evenly in the condensation cure PDMS polymer matrix than the unmodified ZIFs. The alcohol permeability and alcohol/water selectivity for ethanol and 1-butanol remained the same or decreased for membranes made with ligand-exchanged ZIF-71 particles.