Application of conventional polymeric membranes in CO₂ separation processes are limited by the existing trade-off between permeability and selectivity represented by the renowned upper bound. Addition of porous nanofillers in polymeric membranes is a promising approach to transcend the upper bound, owing to their superior separation capabilities. Porous nanofillers entice increased attention over nonporous counterparts due to their inherent CO₂ uptake capacities and secondary transport pathways when added to polymer matrices. Infinite possibilities of tuning the porous architecture of these nanofillers also facilitate simultaneous enhancement of permeability, selectivity and stability features of the membrane conveniently heading in the direction towards industrial realization. This review focuses on presenting a complete synopsis of inherent capacities of several porous nanofillers, like metal organic frameworks (MOFs), Zeolites, and porous organic frameworks (POFs) and the effects on their addition to polymeric membranes. Gas permeation performances of select hybrids with these three-dimensional (3D) fillers and porous nanosheets have been summarized and discussed with respect to each type. Consequently, the benefits and shortcomings of each class of materials have been outlined and future research directions concerning the hybrids with 3D fillers have been suggested.

Membrane technology has the potential to be an eco-friendly and energy-saving solution for the separation of CO₂ from different gaseous streams due to the lower cost and the superior manufacturing features. However, the performances of membranes made of conventional polymers are limited by the trade-off between the permeability and selectivity. Improving the membrane performance through the addition of nanofillers within the polymer matrix offers a promising strategy to achieve superior separation performance. This review aims at providing a complete overview of the recent advances in nanocomposite membranes for enhanced CO₂ separation. Nanofillers of various dimensions and properties are categorized and effects of nature and morphology of the 0D to 2D nanofillers in the corresponding nanocomposite membranes of different polymeric matrixes are discussed with regard to the CO₂ permeation properties. Moreover, a comprehensive summary of the performance data of various nanocomposite membranes is presented. Finally, the advantages and challenges of various nanocomposite membranes are discussed and the future research and development opportunities are proposed.

An in-house designed membrane process suitable for subsea natural gas dehydration was studied. The use of a membrane absorber together with a thermopervaporation (TPV) unit for solvent regeneration in a closed loop enables the effective and clean production of high-pressure natural gas close to the wellhead. This process avoids the continuous chemical injection for preventing hydrate formation in natural gas pipelines. The regeneration of the absorbent agent (triethylene glycol (TEG)) by TPV in the closed loop is highly energy-efficient, owing to the unlimited free cooling energy from the cold subsea water. In this work, the performance of membranes in TPV for TEG regeneration was evaluated experimentally for the first time. Morphological and permeation characterizations of an AF2400 thin-film composite membrane were carried out, and high separation factors outperforming the vapor–liquid equilibrium (VLE) were obtained for the solutions containing various water contents at feed temperatures ranging from 30 to 70 °C. The highest values of a separation factor (128,000) and a permeability (2380 (Barrer)) were obtained for the TEG solution containing 30 wt % water at 30 °C, while the highest water flux (468 (g/m²·h)) was reached at 70 °C. Moreover, the concentration polarization phenomenon induced by the temperature gradient was revealed in the membrane’s vicinity of the feed channel. A 3D computational fluid dynamics simulation was performed over the entire module to correct the driving force for a more precise assessment of the membrane permeance. The temperature and concentration profiles in the membrane module domains were explored, and a good agreement with experimental data was obtained.