Fabrication And Pervaporation Process Intensification Of Polymer-metal Organic Framework Hybrid Membranes

Air pollution has become a public issue in recent years.Automobile exhaust is one of the main sources of air pollutants,and desulfurization of auto-fuel is an effective approach to eliminate the air pollutants.Compared with current hydrodesulfurization process,pervaporative desulfurization process based on membrane separation technology has significant advantages such as high efficiency,low cost and environmental friendliness,showing good prospect of application.Pervaporative desulfurization is a typical process to separate organic mixtures,and the key to high-efficiency process intensification of pervaporative desulfurization is developing membrane materials that combine high permeability,high selectivity and high stability together.However,currently used membrane materials are commonly faced with two restrictive relations,namely the trade-off between permeability and selectivity,together with the trade-off between separation performance and stability.A series of polymer-metal organic framework(MOF)hybrid membranes that combine high permeability,high selectivity and high stability together have been fabricated in this study.1.MIL-101 is incorporated into polydimethyl siloxane(PDMS)matrix to fabricate hybrid membranes.MIL-101 provides low-resistance channels for permeate molecules,as well as increases the fractional free volume of the membrane by interfering with the packing of PDMS chain segments,increasing the membrane permeability;MIL-101 provides preferential adsorption towards thiophene,the organic sulfur impurity of model gasoline,increasing the membrane selectivity;polyvinylidene fluoride(PVDF)substrate provides hydrogen bond interaction with PDMS active separation layer and restricts the excessive swelling of the PDMS active layer,increasing the membrane stability.As a result,the permeation flux with enrichment factor of as-prepared hybrid membrane are increased by 136% with 38%,respectively,compared with pristine PDMS membrane.2.UiO-67-bpydc loaded with Cu(II)is incorporated into PDMS matrix to fabricate hybrid membranes.The loaded groups change the structure of UiO-67-bpydc,and interfere with the polymer chain packing at the polymer-filler interface,increasing the membrane permeability;the bipyridine ligands endow UiO-67-bpydc with affinity towards thiophene via ?-? stacking,increasing the membrane selectivity.As a result,the permeation flux of as-prepared hybrid membrane is increased by 54% without significant change of enrichment factor,compared with PDMS-UiO-67-bpydc hybrid membranes without Cu loading;the permeation flux with enrichment factor of as-prepared hybrid membrane are increased by 74% with 10%,respectively,compared with pristine PDMS membrane.3.CuBTC(HKUST-1)is incorporated into PDMS matrix to fabricate hybrid membranes,and blocked CuBTC is used as a reference material.The active metal sites of CuBTC perform facilitated transport of thiophene,while the channels sieve thiophene preferentially,increasing the membrane selectivity.As a result,the normalized permeation flux with enrichment factor of as-prepared PDMS-CuBTC hybrid membrane and PDMS-blocked CuBTC hybrid membrane are increased by 100% with 75%,and 47% with 7%,respectively,compared with pristine PDMS membrane.4.CuBTC is incorporated into Pebax matrix to fabricate hybrid membranes.CuBTC can interfere with the interchain interaction,and form hydrogen bonds with the polymer chains to tune the membrane structure,increasing the permeability and stability of the membrane;CuBTC can perform facilitated transport funcrtion and sieving function,increasing the selectivity of the membrane.As a result,the permeation flux with enrichment factor of as-prepared hybrid membrane are increased by 36% with 11%,respectively,compared with pristine Pebax membrane.Under higher operating temperatures,Pebax show competitive advantage over PDMS on separation performance.