Substantially Improving CO₂ Permeability and CO₂/CH₄ Selectivity of Matrimid Using Functionalized-Ti₃C₂T

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 Ti₃C₂T MXenes into Matrimid 5218 polymer for efficient CO₂/CH₄ separation. Two-dimensional Ti₃C₂T 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 Ti₃C₂T and the carbonyl groups of Matrimid, promoting enhanced compatibility and dispersion of MXenes within the polymer matrix. The resulting MMMs with 5 wt % Ti₃C₂T showed a 67% increase in CO₂ permeability and an 84% enhancement in CO₂/CH₄ selectivity compared to pristine Matrimid membranes. Surface modification of Ti₃C₂T 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.