Type III porous liquids based on UiO-66 modified by growing the silica layer for CO2 selective separation

Porous liquids（PLs）are a new type of material that combines the permanent cavities of porous solids with the fluidity of liquids, and they have presented broad application prospects in gas capture and separation. However, non-covalent forces are introduced between pore generators and sterically hindered solvents in order to reduce the weak intermolecular forces that often lead to self-aggregation of pore generators. This will result in the formation of an interface layer with direct interactions between pore generators and sterically hindered solvents. Therefore, it is inevitable that the pores and adsorption sites of pore generators will be largely occupied and blocked, leading to a decrease in the sorption capacity of PLs. Herein, we propose a novel interface-protection strategy achieved by introducing a functional interface layer for preparing type III PLs, where UiO-66 is used as the pore generators. And then, SiO 2 is grown on the surface of UiO-66 via the tetraethyl orthosilicate (TEOS) hydrolysis process, thus obtaining a new pore generator UiO-66@SiO 2 with controllable layer thicknesses of SiO 2 . Next, PLs are constructed by using UiO-66@SiO 2 as the new pore generator and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF 6 ) as the sterically hindered solvent, respectively. Thus, the constructed SiO 2 layer transforms the direct interaction between pore generators and sterically hindered solvents, which can protect the internal adsorption sites and pore structures to a large extent. Notably, UiO-66@SiO 2 -PL demonstrates not only promising CO 2 sorption capacity but also excellent CO 2 /N 2 and CO 2 /CH 4 separations. More importantly, the proposed idea of the interface-protection strategy opens a new horizon for constructing PLs with superior separation performance considering the abundant libraries of pore generators and sterically hindered solvents.