Porous liquids (PLs) being formed by engineering permanent porosity into a dense liquid phase provide a promising approach to integrate the merits of flowing liquid systems and porous solid materials. Among the three types of PLs being obtained by liquifying rigid porous hosts (type I), dissolving stiff interior void-containing molecules in flowing liquids (type II), and dispersing porous scaffolds in sterically hindered solvents (type III), Type III-PLs were more straightforward and easier to synthesize, considering the versatile library of rigid porous frameworks and bulky solvent categories. The key factor to synthesizing a high-quality type III-PL lies in the stable dispersion of the solid, porous host in selected bulky solvents to avoid phase separation and particle aggregation/precipitation during long-term storage and utilization. Extensive efforts have been made to achieve ultra-stable dispersion, including but not limited to deploying nanoparticles/nanocrystals with small sizes, surface modification of the porous host to improve compatibility with solvents, and the formation of robust supramolecular interactions.

Recently, Liang-Nian He’s group reported a facile surface deposition strategy to afford diverse type III-PLs possessing ultra-stable dispersion, external structure modification, and enhanced performance in gas storage and transformation by leveraging the expeditious and uniform precipitation of selected metal salts. The Ag(I) species-modified zeolite nanosheets are deployed as the porous host to construct type III-PLs with ionic liquids (ILs) containing bromide anion, leading to stable dispersion driven by the formation of AgBr nanoparticles. The as-afforded type-III PLs display promising performance in CO₂ capture/conversion and ethylene/ethane separation. Property and performance of the as-produced PLs can be tuned by the cation structure of the ILs, which can be harnessed to achieve polarity reversal of the porous host via ionic exchange. The surface deposition procedure can be further extended to produce PLs from Ba(II)-functionalized zeolite and ILs containing [SO₄]²⁻ anion driven by the formation of BaSO₄ salts. The as-produced PLs are featured by well-maintained crystallinity of the porous host, good fluidity and stability, enhanced gas uptake capacity, and attractive performance in small gas molecule utilization. Relevant achievements were published in Adv. Mater., 2023, DOI: 10.1002/adma.202302525.

A) Schematic illustration of the synthesis of stable type III-PLs via a surface deposition strategy from Ag⁺-modified zeolite nanosheets and Br⁻-containing ionic liquids. B) XRD patterns of MCM-22 and MCM22-Ag. C) N₂ isotherms of MCM22-Ag being collected at 77 K. D) Pore size distribution curve of MCM22-Ag being calculated using the Horvath–Kawazoe (H–K) method. E) Elemental mapping, F) SEM, and G) TEM images of MCM22-Ag.