Mixed-linker zeolitic imidazolate framework mixed-matrix membranes for aggressive CO2 separation from natural gas

• Published in: Microporous and mesoporous materials Vol. 192; pp. 43 - 51
• Main Authors: Thompson, Joshua A., Vaughn, Justin T., Brunelli, Nicholas A., Koros, William J., Jones, Christopher W., Nair, Sankar
• Format: Journal Article Conference Proceeding
• Language: English
• Published: San Diego, CA Elsevier Inc 01.07.2014; Elsevier
• Subjects: Chemistry; CO2 capture; Colloidal state and disperse state; Exact sciences and technology; Gas separation; General and physical chemistry; Membranes; Mixed-matrix membranes; Plasticization; Porous materials; Zeolitic imidazolate framework; Zeolitic imidazolate framework; Gas separation; Mixed-matrix membranes; CO2 capture; Plasticization; Gas mixture; Separation; Carbon dioxide; Membrane; capture; CO; Porous material; Natural gas
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/j.micromeso.2013.06.036

•Mixed-linker ZIF synthesis allows control over porosity and pore size distribution.•The mixed-linker ZIFs were used to fabricate composite membranes with Matrimid®.•Composite membranes showed improved selectivity with increasing linker substitution.•This behavior is due to higher effective diffusion selectivity in mixed-linker ZIFs.•Higher CO2 permeability, permselectivity, and plasticization resistance were observed. Zeolitic imidazolate framework (ZIF) materials are a promising subclass of metal–organic frameworks (MOF) for gas separations. However, due to the deleterious effects of gate-opening phenomena associated with organic linker rotation near the limiting pore apertures of ZIFs, there have been few demonstrations of improved gas separation properties over pure polymer membranes when utilizing ZIF materials in composite membranes for CO2-based gas separations. Here, we report a study of composite ZIF/polymer membranes, containing mixed-linker ZIF materials with ZIF-8 crystal topologies but composed of different organic linker compositions. Characterization of the mixed-linker ZIFs shows that the mixed linker approach offers control over the porosity and pore size distribution of the materials, as determined from nitrogen physisorption and Horváth–Kawazoe analysis. Single gas permeation measurements on mixed-matrix membranes reveal that inclusion of mixed-linker ZIFs yields membranes with better ideal CO2/CH4 selectivity than membranes containing ZIF-8. This improvement is shown to likely occur from enhancement in the diffusion selectivity of the membranes associated with controlling the pore size distribution of the ZIF filler. Mixed-gas permeation experiments show that membranes with mixed-linker ZIFs display an effective plasticization resistance that is not typical of the pure polymeric matrix. Overall, we demonstrate that mixed-linker ZIFs can improve the gas separation properties in composite membranes and may be applicable to aggressive CO2 concentrations in natural gas feeds.