Ionic liquid-decorated nanocages for cooperative CO2 transport in mixed matrix membranes.

• An IL-based heterogeneous structure nanofiller ([Hmim][NTf 2 @LDHN) was designed. • IL@LDHN was prepared by impregnating LDHN into a [Hmim][NTf 2 methanol solution. • The [Hmim][NTf 2 @LDHN was used to fabricate MMMs. • The cooperation of [Hmim][NTf 2 and LDHN facilitates CO 2 transport. • The resulting MMMs exhibit superior CO 2 /CH 4 separation performance. An ionic liquid-decorated layered double hydroxide nanocage ([Hmim][NTf 2 @LDHN) was designed and incorporated into Pebax matrix to fabricate high-performance MMMs for CO 2 separation. The [Hmim][NTf 2 on the external surface, interlamellar spacing, and internal hollow core of LDHN plays cooperative roles with LDHN for improving CO 2 permselectivity. First, the [Hmim][NTf 2 on the external surface of LDHN absorbs more CO 2 molecules than CH 4 , improving CO 2 /CH 4 selectivity. Then, the captured CO 2 permeates into LDHN shells and are dissolved by [Hmim][NTf 2 in the interlamellar spacing of LDNH. The dissolved CO 2 combines quickly with CO 3 2− carriers existed in LDHN itself, accelerating CO 2 transport. Third, the [Hmim][NTf 2 encapsulated in the internal hollow core of the LDHN has an ultrahigh CO 2 capacity, which increases both CO 2 permeability and selectivity. The cooperation of [Hmim][NTf 2 and LDHN significantly enhances CO 2 separation performance. In particular, under humidified conditions the Pebax/[Hmim][NTf 2 @LDHN-6 MMM presents optimal separation performance with a CO 2 permeability of 644 ± 25 Barrer and a CO 2 /CH 4 separation factor of 34 ± 0.53, which transcends the upper bound relationship developed by Robeson (2008). The nanofillers combining ILs with nanocages exhibit a promising prospect to fabricate high-performance MMMs for gas separations. [ABSTRACT FROM AUTHOR]