(160d) Novel Supramolecular Organic Framework (SOF) Based Mixed Matrix Membranes (MMMs) for CO2/CH4, CO2/N2, and N2/CH4, Separations

Zoban V. Singh¹, LiLi Tan², Matthew G. Cowan^1,2, Wei Zhang², Douglas L. Gin^1,2, and Richard D. Noble¹

(1) Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO, (2) Department of Chemistry, University of Colorado, Boulder, CO

Abstract: Supramolecular organic frameworks (SOFs) represent a new class of microporous solids that display excellent CO₂-light-gas selectivity. Analogous to inorganic zeolites, SOFs conduct high-selectivity CO₂-light gas separation via a similar sorption based mechanism. However, forming large-scale membranes from pure microporous solids, such as zeolites, is challenging due to defect-spaces arising between the tight packing of zeolite crystals. We have previously presented a series of mixed-matrix membranes containing zeolites, which combine the excellent CO₂-light gas separation properties of the zeolite with the processability of a polymer. In contrast to zeolites, which are insoluble, SOFs can be readily dissolved into many conventional solvents, making solvent-based casting fabrication techniques for MMM formulation a convenience. In this talk, we present a new SOF based MMM platform. Upon crystallization and complete activation of the SOF at elevated temperatures, CO₂ permeability and CO₂-light gas selectivity values skyrocket. Due to thermal crosslinks that form in the polymer matrix at higher temperaturesâ??a phenomenon pervasively reported in the literatureâ??and due to the formation of larger crystalline surface areas in the SOF at elevated temperatures, sorption and diffusivity based permselectivity synergize. For these reasons, the separation performance of the new MMMs created with SOFs display incredibly high CO₂/CH₄, CO₂/N₂, and N₂/CH₄ selectivity. We believe, these are amongst the most selective MMMs ever created for the aforementioned gas pairs and represents a breakthrough in the development of high performance membranes for commercial applications given that all three separations hold major industrial and environmental significance. In addition to the excellent separation properties of the SOF, the ability to dissolve the dispersed phase into a solvent that can co-dissolve the polymer matrix, presents a significant advantage towards ease of processability and scale-up.