Interface layer-assisted construction of metal organic framework based porous liquids for high performance CO₂ selective separation

Porous liquids (PLs) are a novel class of materials that integrate porosity and fluidity, and have garnered significant interest in gas capture and separation especially the type III PLs. However, current methods for preparing type III PLs typically involve dispersing pore generators in sterically hindered solvents, which may lead to potential loss of permanent pores or adsorption sites within pore generators. Therefore, a novel strategy of “interface layer-assisted construction” was proposed for preparing PLs by introducing an interfacial layer, where in UiO-66 serves as the old pore generator. The new pore generator, UiO-66@ZIF-8, is obtained by growing a dense ZIF-8 interfacial layer on the surface of UiO-66. Subsequently, the new pore generator UiO-66@ZIF-8was dispersed in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf₂]) sterically hindered solvent to fabricate PLs. Consequently, the constructed ZIF-8 layer alters the direct interaction between the pore generator and sterically hindered solvents, enabling substantial preservation of internal adsorption sites and pore structures through indirect interactions. As expected, the as-synthesized UiO-66@ZIF-8 PLs not only demonstrate excellent CO₂ sorption capacity (0.52 mmol/g, 303 K, 2.5 bar) and low viscosity (0.08 Pa·s at 25 °C), but also exhibit outstanding CO₂/CH₄ and CO₂/N₂ separation performance. Notably, this approach offers a promising advancement in the synthesis of high performance type III PLs interms how to design the pore generators, providing new perspectives for their applications in gas separation.