Tröger 's base mixed matrix membranes for gas separation incorporating NH2-MIL-53(Al) nanocrystals

Abstract

The rigid Tröger's base microporous polymers were utilized to fabricate mixed matrix membranes with NH2-MIL-53 (Al) nanocrystals. Such N containing polymers have the ability to interact with NH2-MIL-53 (Al), therefore yielding transparent, robust, and plasticization–resistant hybrid membranes. The resulting membranes show a remarkable increase in gas permeability up to 3 times as a result of improved gas diffusivity and solubility without the selectivity loss. Much more improvements in CO2 solubility arise from the presence of CO2-adsorbing sites in Tröger's base polymers and the CO2-selective adsorption properties of NH2-MIL-53 (Al), correspondingly leading to increased CO2 solubility selectivity. The gas separation performance shifts toward Robeson upper bonds upon the addition of MOFs. Particularly, the H2/CH4 separation performance overcomes the 2008 Robeson upper bond. In mixed gas feeds, the membranes display CO2 gas permeability up to 308 Barrer and CO2/N2 and CO2/CH4 mixed gas selectivities of 25.4 and 23.6 with virtually no evidence of plasticization. Much higher mixed-gas selectivity than permselectivity in these membranes are strongly correlated with the strongly adsorbing CO2 gas molecules blocking transport of large size molecules.