MIL‐53(Al) as a Versatile Platform for Ionic‐Liquid/MOF Composites to Enhance CO(2) Selectivity over CH(4) and N(2)

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(2) separation performance of MIL‐53(Al). CO(2), CH(4), and N(2) 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(2)/CH(4) and CO(2)/N(2) selectivities of the MOF. Of the composite materials that were tested, [BMIM][PF(6)]/MIL‐53(Al) exhibited the largest increase in CO(2)/CH(4) selectivity, 2.8‐times higher than that of pristine MIL‐53(Al), whilst [BMIM][MeSO(4)]/MIL‐53(Al) exhibited the largest increase in CO(2)/N(2) selectivity, 3.3‐times higher than that of pristine MIL‐53(Al). A comparison of the CO(2) separation potentials of the IL/MOF composites showed that the [BMIM][BF(4)]‐ and [BMIM][PF(6)]‐incorporated MIL‐53(Al) composites both showed enhanced CO(2)/N(2) and CO(2)/CH(4) 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.