Breaking solubility of metal-organic cages via polymer carrier for concentrated type II porous liquid to extract <i>n</i>-alkanes.

Yang, Shuaibo; Han, Yu; Cui, Mifen; Tang, Jihai; Qiao, Xu; Zhang, Zhuxiu · Sci Adv · 2026

basic_science · Level V

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Abstract

Type II porous liquids that exhibit host-guest properties derived from molecular cages are of potential utility in liquid-liquid separations; however, those with metal-organic cages (MOCs) as pore hosts are extremely rare due to the limited solubility of MOCs in cavity-excluded solvents. Here, we report the use of polyvinylpyrrolidone (PVP) to deliver polyoxovanadate-organic hybrid cages (HD) in polyethylene glycol (PEG) for a concentrated type II porous liquid (HD<sub>PVP</sub>/PEG). Structural characterizations and modeling studies collectively confirm that the PVP-PEG compatibility and the HD-PVP interaction enable the high HD concentration in PEG. The minimal loading of PVP coupled with the steric hindrance of PVP and PEG ensure the permanent porosity and room-temperature fluidity. HD<sub>PVP</sub>/PEG exhibits high uptake and selectivity toward C<sub>5</sub>-C<sub>7</sub> <i>n</i>-alkanes over their branched isomers due to the host-guest interactions between HD and <i>n</i>-alkanes. The design strategy of HD<sub>PVP</sub>/PEG was successfully extended to other typical MOCs and commonly-used cavity-excluded solvents.