Abstract
Metal-organic frameworks (MOFs) were supported on polymer membrane substrates for the fabrication of composite polymer membranes based on unmodified and modified polymer of intrinsic microporosity (PIM-1). Layers of two different MOFs, zeolitic imidazolate framework-8 (ZIF-8) and Copper benzene tricarboxylate ((HKUST-1), were grown onto neat PIM-1, amide surface-modified PIM-1 and hexamethylenediamine (HMDA) -modified PIM-1. The surface-grown crystalline MOFs were characterized by a combination of several techniques, including powder X-ray diffraction, infrared spectroscopy and scanning electron microscopy to investigate the film morphology on the neat and modified PIM-1 membranes. The pure gas permeabilities of He, H2, O2, N2, CH4, CO2 were studied to understand the effect of the surface modification on the basic transport properties and evaluate the potential use of these membranes for industrially relevant gas separations. The pure gas transport was discussed in terms of permeability and selectivity, highlighting the effect of the MOF growth on the diffusion coefficients of the gas in the new composite polymer membranes. The results confirm that the growth of MOFs on polymer membranes can enhance the selectivity of the appropriately functionalized PIM-1, without a dramatic decrease of the permeability.
Highlights
Polymeric membranes for gas separation are used for highly energy-efficient industrial separations
This paper proposes a new approach to develop symmetric composite metal-organic frameworks (MOFs) based membranes by growing MOF particles on the surface of polymer membranes as an alternative to their dispersion inside the polymer matrix [17]
The thickness of zeolitic imidazolate framework-8 (ZIF-8) layer on the surface polymer membranes can be tailored by repeated repeated cyclic immersion of theZIF-8/polymers of intrinsic microporosity (PIMs)-1 previous ZIF-8/PIM-1 into a fresh solution of the cyclic immersion of the previous membranesmembranes into a fresh solution of the precursors of precursors of ZIF-8 a number of times
Summary
Polymeric membranes for gas separation are used for highly energy-efficient industrial separations. Many different synthetic techniques have been reported to deposit a MOF film on solid surfaces, including surface functionalization of the solid substrates to form self-assembled monolayers (SAMs) [5,19,20,21,22,23,24,25] These SAMs provide active sites for promoting the heterogeneous nucleation and the growth of MOF crystals and enhance the adhesion between MOF particles and supports as well [17,26]. The surface of PVAc was chemically modified to generate reactive carboxylic groups to enhance the compatibility between the HKUST-1 film and the polymer support, and to promote heterogeneous nucleation of crystal growth.
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