A comprehensive review on two-dimensional nanomaterials-mixed matrix membranes for sustainable CO2 separation: from molecular engineering design to efficient modification strategies

Abstract

Two-dimensional nanomaterials (2DNMs) are promising for mixed matrix membranes (MMMs) in gas separation but face challenges such as aggregation, interfacial defects, plasticization, and aging. The present review examines key obstacles and strategies to enhance 2DNM-polymer interactions, aiming for durable, high-efficiency membranes. To address such challenges, multifaceted strategies aimed at enhancing the interfacial interaction between 2DNMs and the polymer matrix are examined. Optimizing intrinsic 2DNM properties, pore size, interlayer spacing, and lateral-to-thickness ratio, can improve gas selectivity. Controlling the number of layers, enhancing solubility, and leveraging facilitated transport properties are also crucial. Surface functionalization, such as grafting ionic liquids or macromolecules, enhances compatibility while blending chain molecules fine-tunes membrane performance. Synergistic combinations of 2DNMs with other nanomaterials, including 0D, 1D, and 3D structures, significantly improve gas transport and mechanical strength. Additionally, orientation enhancement techniques, such as applying magnetic or electric fields during fabrication, align 2DNMs within the matrix to optimize gas separation pathways. The insights gained from the study of 2DNMs extend beyond CO₂ separation and are applicable to other gas mixtures. Such principles play a crucial role in shaping the next generation of MMMs, with broad implications for industrial and environmental applications.