(464g) Enhancing CO2/CH4 Separation Performance and Mechanical Strength of Mixed-Matrix Membrane Via Combined Use of Graphene Oxide and ZIF-8

Gas separation using high-performance membranes have demonstrated itself as an energy-efficient and environment-benign process that is capable of replacing the conventional energy-intensive processes. In general, polymeric membranes have been widely incorporated in view of their good mechanical stability and processability. However, the trade-off effect between gas permeability and selectivity severely limits their future development of gas separation. Thus, mixed-matrix membranes (MMMs) that utilized synergistic effect of both polymer matrix and nanoporous fillers have been a focus of attention to researchers. This is because the addition of nanoporous materials acts as an efficient aid to favor selective gas transport. Nevertheless, the utilization of one type of filler tends to optimize either gas permeability or selectivity in gas mixtures. Therefore, in this context, an effective and feasible strategy in improving both gas permeability and selectivity was proposed by utilizing binary fillers.

High-performance MMMs that comprise both zeolitic imidazolate framework-8 (ZIF-8) and graphene oxide (GO) were synthesized to realize excellent CO₂/CH₄ separation. The incorporation of ZIF-8 nanocrystals alone in ODPA-TMPDA polyimide can be used to significantly enhance CO₂ permeability compared with that of pure ODPA-TMPDA. Meanwhile, the addition of a GO nanostack alone in ODPA-TMPDA contributes to improved CO₂/CH₄ selectivity. Hence, a composite membrane that contains both fillers displays significant enhancements in CO₂ permeability (up to 60%) and CO₂/CH₄ selectivity (up to 28%) compared with those of pure polymeric membrane. Furthermore, in contrast to the ZIF-8 mixed-matrix membrane, which showed decreased mechanical stability, it was found that the incorporation of GO could improve the mechanical strength of mixed-matrix membranes. Overall, the synergistic effects of the use of both fillers together are successfully demonstrated in this paper. Such significant improvements in the mixed-matrix membrane’s CO₂/CH₄ separation performance and mechanical strength suggest a feasible and effective approach for potential biogas upgrading and natural gas purification.