Metal-organic framework-based porous liquids via surface functionalization engineering for selective gas adsorption

Porous liquids (PLs) combine the distinct porosity of solids with the fluidity of liquids, offering new solutions for carbon capture, membrane separation, and more. This study introduces the development of unique UIO-66-PLs through a meticulous surface functionalization strategy, using surface-modified UIO-66-(OH) 2 with the organic oligomer SIT8378.3 (SIT) and polyether amines (PEAs) of various molecular weights (M1000, M2070, and M3085) as the hindering solvents. The resulting UIO-66-PLs exhibit exceptional stability and dispersibility in both aqueous and organic environments. Importantly, benefiting from preserving UIO-66-(OH) 2 ′s porosity in PLs, the affinity of PEAs’ ethylene oxide segments for CO 2 via Lewis acid-base interactions, and additional free space within organic chains, UIO-66-PLs revealed enhanced CO 2 adsorption capabilities, particularly for CO 2 over N 2 . Encouragingly, CO 2 adsorption of UIO-66-PLs was enhanced by 117.54 % (UIO-66-M1000), 106.01 % (UIO-66-M2070), and 22.45 % (UIO-66-M3085) in capacity relative to the respective pure organic outer layer. It is also observed that while surface engineering improves gas adsorption performance, PEAs with a high molecular weight may partially block UIO-66-(OH) 2 pores, decreasing gas adsorption capacities. Our research showcases the potential of UIO-66-PLs in gas storage and separation applications, offering a new approach to developing materials functionalized with customized organic molecular weights for advanced CO 2 capture technologies.