Pebax-based membrane filled with photo-responsive Azo@NH2-MIL-53 nanoparticles for efficient SO2/N2 separation

Challenges and recent advances in MOF-based gas separation membranes

Membrane-based gas separation, characterized by a small footprint, low energy consumption and no pollution, has gained widespread attention as an environmentally friendly alternative to traditional gas separation. Metal-organic-frameworks (MOFs) are considered to be one of the most promising membrane-based gas separation materials because of their large specific surface area and high porosity. One of the hottest studies at the moment is how to utilize the characteristics of MOFs to prepare higher performance gas separation membranes. This paper provides a review of gas separation membranes used in recent years. Firstly, the synthesis methods of MOFs and MOF membranes are briefly introduced. Then, methods to improve the membrane properties of MOFs are described in detail, and include applications of lamellar MOFs, ionic liquid (IL) spin coating, functionalization of MOFs, defect engineering and mixed fillers. In addition, the challenges of MOF-based gas separation membranes are presented, including pore size, environmental disturbances, plasticization, interfacial compatibility, and so on. Finally, based on the current development status of the MOF membranes, the development prospects of MOF gas separation membranes are discussed. It is hoped to provide reliable and complete ideas for researchers to prepare high-performance gas separation membranes in the future.

Deep eutectic solvent-based blended membranes for ultra-super selective separation of SO2

SO2 is a major atmospheric pollutant leading to acid rain and smog. As a new generation of green solvents, deep eutectic solvents (DESs) have been widely investigated for gas capture. Nevertheless, studies on DES-based membranes for SO2 separation are yet minimal. Herein, we devised polymer/DES blended membranes comprising 1-butyl-3-methyl-imidazolium bromide ([Bmim]Br)/diethylene glycol (DEG) DES and poly (vinylidene fluoride) (PVDF), and these membranes were firstly used for selective separation of SO2 from N2 and CO2. The permeability of SO2 reaches up to 17480 Barrer (0.20 bar, 40 ºC) in PVDF/DES blended membrane containing 50 wt% of [Bmim]Br/DEG (2:1), with ultrahigh SO2/N2 and SO2/CO2 selectivity of 3690 and 211 obtained, respectively, far exceeding those in the state-of-the-art membranes reported in literature. The highly-reversible multi-site interaction between SO2 and [Bmim]Br/DEG DES was revealed by spectroscopic analysis. Furthermore, the PVDF/DES blended membrane was also able to efficiently and stably separate SO2/CO2/N2 (2.5/15/82.5%) mixed gas for at least 100 h. This work demonstrates for the first time that [Bmim]Br-based DESs are very efficient media for membrane separation of SO2. The easy preparation, low cost and high performance enable polymer/DES blended membranes to be promising candidates for flue gas desulfurization.