Porous liquids based on ZIF-67@ZIF-8 through the strategy of interface layer reconstruction for CO₂ selective sorption

Porous liquids (PLs) are a new type of porous materials that combine both the porosity of solids and the fluidity of liquids, which have attracted widespread attention. In this paper, we report a novel type III porous liquid through the interfacial layer reconstruction strategy, which are composed of ZIF-67@ZIF-8 as porous cavity and ionic liquid [P_6,6,6,14][NTf₂] as sterically hindered solvents, respectively. At 25 °C, it showed superior fluidity and the viscosity of PLs is 0.1911 Pa·s (25 °C). Moreover, ZIF-67@ZIF-8 PLs have the potential for CO₂/N₂ and CO₂/CH₄ selective separation. Under 10.0 bar, the CO₂ adsorption capacity of ZIF-67(S)@ZIF-8-PLs is 1.37 mmol/g that is higher than that of ZIF-67(S)-PLs. Under the same conditions, the CO₂ adsorption capacity of PLs is 22.68 times higher than that of N₂. Under 2.5 bar, ZIF-67@ZIF-8 PLs showed very low CH₄ sorption capacity of 0.005 mmol/g, which is less than that of CO₂ (0.279 mmol/g). Notably, this study opens a new horizon to prepare PLs with superior gas selective separation based on interfacial layer reconstruction strategy considering the multiple structures of metal–organic frameworks (MOFs) as porous cavities.