Preparation of stable multilayer PDMS composite pervaporation membrane incorporated with in-situ transformed metal organic frameworks for enhanced butanol recovery

In this study, stable and non-defective multilayer polydimethylsiloxane (PDMS) composite pervaporation mixed matrix membranes incorporated with in-situ transformed metal organic frameworks was successfully synthesized via ligand vapor phase infiltration and spin-coating. Metal zinc sources were uniformly distributed in PDMS which were in-situ transformed into homogeneous zeolitic imidazolate framework-8 (ZIF-8) nanoparticles, effectively alleviating the aggregation of ZIF-8. Thermal cross-linking of PDMS and the formation of MOFs occurred simultaneously, omitting the complicated preparation and re-dispersion steps of MOF nanoparticles. MOF nanoparticles and PDMS formed a more stabilized composite structure by in-situ transformation, in which PDMS and metal of MOFs can interact with the -Si-O- of silane coupling groups on membrane surface to construct solid multilayer composite membrane, ensuring long-term stability. Moreover, with the aid of hydrophobic interlayer, polymer infiltration into channels of substrate was restricted and casting solution spread out smoothly, facilitating the formation of defect-free PDMS selective layer. Various techniques including Attenuated Total Reflection-Fourier Transform Infrared Spectrometer, Field Emission Scanning Electron Microscopy, Atomic Force Microscope and X-ray Diffraction were applied to explore the morphology, composition and structure of nanoparticles and membranes, and pervaporation tests were taken to investigate the behavior of hydrophobic polymer-based multilayer membranes. For the recovery of low concentration n-butanol, the prepared non-defective multilayer TAO/ZIF-8/K-PDMS composite membrane displayed excellently total permeate flux of 2890 g m−2 h−1 with competitive separation factor of 40.3.