MIL-53(Al) as a Versatile Platform for Ionic-Liquid/MOF Composites to Enhance CO Selectivity over CH and N.

Five different imidazolium-based ionic liquids (ILs) were incorporated into a metal-organic framework (MOF), MIL-53(Al), to investigate the effect of IL incorporation on the CO separation performance of MIL-53(Al). CO , CH , and N adsorption isotherms of the IL/MIL-53(Al) composites and pristine MIL-53(Al) were measured to evaluate the effect of the ILs on the CO /CH and CO /N selectivities of the MOF. Of the composite materials that were tested, [BMIM][PF ]/MIL-53(Al) exhibited the largest increase in CO /CH selectivity, 2.8-times higher than that of pristine MIL-53(Al), whilst [BMIM][MeSO ]/MIL-53(Al) exhibited the largest increase in CO /N selectivity, 3.3-times higher than that of pristine MIL-53(Al). A comparison of the CO separation potentials of the IL/MOF composites showed that the [BMIM][BF ]- and [BMIM][PF ]-incorporated MIL-53(Al) composites both showed enhanced CO /N and CO /CH selectivities at pressures of 1-5 bar compared to composites of CuBTC and ZIF-8 with the same ILs. These results demonstrate that MIL-53(Al) is a versatile platform for IL/MOF composites and could help to guide the rational design of new composites for target gas-separation applications.