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Membrane gas separation possesses the advantages of energy-saving, simple operation, environmental friendliness, and economic efficiency compared to traditional separation processes. Carbon molecular sieve (CMS) membranes have attracted increasing interest due to their superior chemical resistance and thermal stability compared to polymer membranes, as well as their ability to overcome the limitations of the trade-off between permeability and selectivity commonly present in polymer membranes. Specifically, polyimides (PIs) and polymers of intrinsic microporosity (PIMs), which have the intrinsic advantages of designable structures, superior gas separation performances, and good thermal and mechanical strength, serve as excellent precursors for making CMS membranes. Although significant progress has been achieved in the study of PI- and PIM-derived CMS membranes in the past few decades, there is still a lack of systematic research on their pyrolysis protocols. Herein, the current work reviewed the research progress in PI- and PIM-derived CMS membranes in the field of CO2 separation (CO2/CH4, CO2/N2 and CO2/H2) and olefin/paraffin separation, as well as the process simulation and techno-economic analysis of CMS membrane based gas separation processes. In particular, the effect of pyrolysis protocols including pyrolysis temperature, ramping rate, pyrolysis atmosphere and soaking time on the pore structure and gas separation performance of PI- and PIM-derived CMS membranes were systematically summarized and discussed. In addition, similar to CMS membranes made via other precursors, PI and PIM precursors also play an important role in the final CMS membrane separation performance. Generally, CMS membranes fabricated from PI and PIM precursors with higher free volume exhibited better gas separation performance. Overall, PIs and PIMs have been proven to be promising candidate precursors for CMS membrane fabrication. In addition, this review also offers perspectives and future research directions for next-generation PI- and PIM-derived CMS membranes for various gas separation applications. [ABSTRACT FROM AUTHOR]

Membrane-mediated separation has gained significant attention as a promising strategy for CO2 separation. The continuous quest for membrane materials with improved CO2 separation performance remains a priority in advancing membrane gas separation technologies. Troger's base (TB), characterized by its rigid V-shaped bridged bicyclic linking group, presents an excellent building block for enhancing polymer rigidity and hindering chain packing, thereby improving the gas separation performance. Despite considerable progress which has been made on TB polymeric membranes over the past few years, a comprehensive review on this topic is still lacking. Herein, the development of membranes based on TB polymers for CO2 separation in the past ten years is summarized and discussed. Specifically, pure TB polymeric membranes, functionalized TB polymeric membranes, TB polymer based mixed-matrix membranes (MMMs), and TB polymer based carbon molecular sieve (CMS)/thermal rearranged (TR) membranes are discussed, targeting separation performance. Finally, conclusions are drawn on the progress of CO2 separation membranes based on TB polymers, with perspectives for future development also presented. [ABSTRACT FROM AUTHOR]

A novel, directly‐injected solid fiber sorbent is synthesized from a solvent‐stable, epoxy‐crosslinked basic immobilized amine sorbent (BIAS) for CO2 capture. Leach resistance of the BIAS organics toward 1‐methyl‐2‐pyrrolidone/H2O (90/10, fiber solvent) reaches near 100% at the expense of CO2 capture and is achieved by increasing the extent of crosslinking. The optimized fiber sorbent, prepared with an N,N‐diglycidyl‐4‐glycidyloxyaniline/polyethylenimine (PEI)‐0.35/1 wt. ratio, retains 79.2% of PEI and captures 0.37 (direct air capture [DAC]) and 0.67 (postcombustion) mmol CO2g‐fiber−1. A nonoptimized prototype hollow fiber exhibits a stable 0.2 mmol CO2g‐fiber−1 during DAC cycling and is assembled into a ten‐fiber module. These results demonstrate a large step toward practical application of this material. [ABSTRACT FROM AUTHOR]

Membrane‐based gas separations are energy efficient processes; however, major challenges remain to develop high‐performance membranes enabling the replacement of conventional separation processes. Herein, a new fluorinated MOF‐based mixed‐matrix membrane is reported, which is formed by incorporating the MOF crystals into selected polymers via a facile mixed‐matrix approach. By finely controlling the molecular transport in the channels through the MOF apertures tuned by metal pillars and at the MOF‐polymer interfaces, the resulting fluorinated MOF‐based membranes exhibit excellent molecular sieving properties. These materials significantly outperform state‐of‐the‐art membranes for simultaneous removal of H2S and CO2 from natural gas—a challenging and economically important application. The robust fluorinated MOFs (NbOFFIVE‐1‐Ni, AlFFIVE‐1‐Ni), pave a way to efficient membrane separation processes that require precise discrimination of closely sized molecules. Separate ways: New fluorinated metal–organic framework (MOF)‐based mixed‐matrix membranes with finely controlled molecular transport in the channels through the MOF aperture exhibit excellent molecular‐sieving properties that significantly outperform state‐of‐the‐art membranes for simultaneous removal of H2S and CO2 from natural gas. [ABSTRACT FROM AUTHOR]

Abstract: Membrane‐based separations offer great potential for more sustainable and economical natural gas upgrading. Systematic studies of CO2/CH4 separation over a wide range of temperatures from 65 °C (338 K) to as low as −40 °C (233 K) reveals a favorable separation mechanism toward CO2 by incorporating Y‐fum‐fcu‐MOF as a filler in a 6FDA‐DAM polyimide membrane. Notably, the decrease of the temperature from 308 K down to 233 K affords an extremely high CO2/CH4 selectivity (≈130) for the hybrid Y‐fum‐fcu‐MOF/6FDA‐DAM membrane, about four‐fold enhancement, with an associated CO2 permeability above 1000 barrers. At subambient temperatures, the pronounced CO2/CH4 diffusion selectivity dominates the high permeation selectivity, and the enhanced CO2 solubility promotes high CO2 permeability. The differences in adsorption enthalpy and activation enthalpy for diffusion between CO2 and CH4 produce the observed favorable CO2 permeation versus CH4. Insights into opportunities for using mixed‐matrix membrane‐based natural gas separations at extreme conditions are provided. [ABSTRACT FROM AUTHOR]

Scalable fiber sorbents are a key milestone toward a viable hollow fiber rapid temperature swing adsorption system. Directly Spun Epoxy-Crosslinked Polyethylenimine Fiber Sorbents for Direct Air Capture and Postcombustion Capture of CO2 Directly injected/spun fiber sorbents synthesized from solvent-stable, crosslinked, immobilized amine sorbents remove CO SB 2 sb under direct air capture (400 ppm CO SB 2 sb ) and postcombustion (14% CO SB 2 sb ) capture conditions. [Extracted from the article]

Directly injected/spun fiber sorbents synthesized from solvent‐stable, crosslinked, immobilized amine sorbents remove CO2 under direct air capture (400 ppm CO2) and postcombustion (14% CO2) capture conditions. Scalable fiber sorbents are a key milestone toward a viable hollow fiber rapid temperature swing adsorption system. More details can be found in article number 2200356, Walter C. Wilfong, Shouliang Yi and co‐workers. [ABSTRACT FROM AUTHOR]