(573c) CO2 Separation Performance of Ti3C2-Polyimide Mixed-Matrix Membranes

Membrane gas-separation processes are a promising alternative to the energy-intensive conventional processes that are currently being used in the oil and gas industry. Despite the tremendous potential of polymeric membranes, the inverse relationship between gas permeability and selectivity has restricted their widespread applications. Membranes fabricated from composites formed by embedding nanomaterials into a continuous polymeric phase; i.e., mixed-matrix membranes (MMMs), have offered a pragmatic solution to defy the selectivity-permeability tradeoff [1,2]. Polyimide membranes have been shown to have high gas selectivity, however, their low free volume results in reduced gas permeability [3]. Numerous studies have demonstrated the potential of two-dimensional (2D) nanosheets, including graphene oxide (GO), MoS₂, and MXenes, for use in MMMs [4]. These materials possess high aspect ratios and rich chemistry allowing for strong interactions with polymer chains and the fabrication of defect-free MMMs with less interfacial voids and agglomeration. For example, –OH surface terminations on MXene's surface can be modified to enhance the compatibility of a polymer/nanomaterial interface through traditional silanol chemistry [5]. MXenes are a family of 2D transition metal carbides, carbonitrides, and nitrides nanomaterials with high aspect ratios, tunable surface chemistry, negative zeta potential, and unique 2D lamellar structure. These properties can enhance dispersity of MXenes in various solvents including aprotic ones. So far, the separation performance of rubbery polymeric membranes was improved by the introduction of Ti₃C₂ MXene, because of enhancing CO₂ solubility selectivity, molecular-sieving ability of MXene interlayers, and adjusting the gas transport pathway [1].

In this work, the feasibility of creating Matrimid®5218 (a glassy polyimide)-MXene MMMs with optimal physical and gas separation properties is explored. Specifically, we investigate the hypothesis that the abundant carbonyl groups in Matrimid can interact with hydroxyl groups of Ti₃C₂ MXenes to provide defect-free membranes. Furthermore, the effect of amine functionalization of MXene surface on the CO₂ separation performance is evaluated. The existence of unoccupied amine groups on the surface presents an opportunity for development of high-performance membranes. This approach was derived from several studies on the amine functionalization of different metal-organic frameworks. The method provides enhanced gas adsorption properties and interaction between the polymer matrix and amine groups. This renders an appealing prospect for creating MXene that is functionalized with amines, resulting in a material with exceptional CO₂ adsorption capacity. To characterize the morphological, thermal, and mechanical properties of the prepared membranes, Fourier-transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, and scanning electron microscopy are used. Gas permeation tests are conducted to evaluate the gas transport behavior of the fabricated membranes.

References

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