Substantially Improving CO2 Permeability and CO2/CH4 Selectivity of Matrimid Using Functionalized-Ti3C2Tx

Mixed-matrix membranes (MMMs) with favorable interfacial interactions between dispersed and continuous phases offer a promising approach to overcome the traditional trade-off between permeability and selectivity in membrane-based gas separation. In this study, we developed free-standing MMMs by embedding pristine and surface-modified Ti3C2Tx MXenes into Matrimid 5218 polymer for efficient CO2/CH4 separation. Two-dimensional Ti3C2Tx with adjustable surface terminations provided control over these critical interfacial interactions. Characterization (Raman spectroscopy, XPS, DSC, FTIR) indicated the formation of hydrogen bonds between the termination groups on Ti3C2Tx and the carbonyl groups of Matrimid, promoting enhanced compatibility and dispersion of MXenes within the polymer matrix. The resulting MMMs with 5 wt % Ti3C2Tx showed a 67% increase in CO2 permeability and an 84% enhancement in CO2/CH4 selectivity compared to pristine Matrimid membranes. Surface modification of Ti3C2Tx using [3-(2-aminoethylamino)propyl]trimethoxysilane (AEAPTMS) further enhanced compatibility, leading to MMMs with 140% higher CO2 permeability and 130% greater CO2/CH4 selectivity. Molecular simulations suggested that AEAPTMS functionalization improved interfacial interactions with Matrimid chains, increasing the affinity of MXenes toward CO2 molecules. Additionally, the elongation of gas pathways, polymer chain disruption, and the presence of interlayer nanogalleries contributed positively to the enhanced separation performance. This work provides insights into tailoring nanomaterial–polymer interfaces to address the challenges of gas separation, paving the way for environmentally friendly CO2 separation technologies.