Enhanced hydrogen separation through H2-Selective PMMA/CAU-1 thin film nanocomposite membrane

Abstract

The amine-functionalized Christian-Albrechts-University-1 (CAU-1) metal–organic framework (MOF) possesses intrinsic structural features ideally suited for hydrogen (H2) separation, with pore apertures closely matching the molecular size of hydrogen, thereby enabling selective hydrogen transport via molecular sieving. The physicochemical and structural tailoring of CAU-1 holds immense potential for gas separation thin-film nanocomposite (TFN) membranes yet it remains largely unexplored. This work presents the first systematic investigation of CAU-1 incorporation confined within a thin PMMA selective layer supported on a polysulfone (PSF) substrate, elucidating its influence on the interfacial structure, gas transport pathways, and hydrogen separation performance of polymethyl methacrylate (PMMA)/CAU-1 TFN membranes. Morphological analyses revealed the successful formation of thin, dense, and defect-free TFN exhibiting excellent polymer-filler compatibility with no observable interfacial voids, while thermogravimetric analysis demonstrated excellent thermal stability up to 360 ◦C. The optimized PMMA/CAU0.5 membrane achieved an H2 permeability of 294.43 Barrer, with ideal selectivities of 4.91, 6.30 and 5.03 against carbon dioxide (CO2), nitrogen (N2), and methane (CH4), respectively, representing respective improvements of 11%, 42%, and 51% over pristine PMMA. Under mixed-gas conditions, the H2/CO2 separation factor surpassed the Robeson upper limit indicating the effective H2-selective transport properties. These findings highlight the pivotal role of CAU-1 in creating microporous, H2-selective transport pathways, demonstrating the potential of PMMA/CAU-1 TFN membranes for enhanced hydrogen purification.