RETHINK NANOCOMPOSITE MEMBRANE DESIGN USING 3-DIMENSIONAL ORGANIC MACROCYCLIC MOLECULES FOR ULTRA-EFFICIENT GAS SEPARATION

Abstract

Utilizing nanoparticles with molecular-sieving characteristics in polymer membranes has received explosive attention in recent years for targeting more energy-efficient environmentally important gas separations, such as CO2 capture and hydrogen purification. However, conventional nanocomposite membrane designs via physical mixing face many unsurpassable issues that limit their performance and scalability. This thesis reinvented nanocomposite membranes using an underexplored class of organic macrocyclic molecules, named calixarenes, such that both state-of-the-art gas separation performance and the circumvention of conventional issues were achieved. Their unique co-existence of intrinsic angstrom-scale size-sieving 3D open cavity, small molecular size and complete protic-solvent solubility enabled homogeneous infiltration of solvent-dissolved calixarenes into already fabricated solid-state dense polymer membranes. They could then serve as molecular gatekeepers that effectively size-discriminate different gas species. Size-tunability of calixarenes was also investigated using various cavity dimensions. In addition, favorable tuning of the polymer microporous structure was achievable via copolymerizing highly functionalizable calixarenes into polymer backbones.