Microscopic Mechanism of Gas Sorption in Type II Porous Liquid of Metal-Organic Polyhedra

Porous liquids (PLs) combine permanent microporosity with fluidity, showing great potential for gas adsorption and separation. However, their rational design is hindered by a vague microscopic understanding of gas transport. Herein, Type II PLs are designed by dissolving metal-organic polyhedra (MOPs) grafted with poly(dimethylsiloxane) (PDMS) into a PDMS melt. X-ray scattering confirms the uniform dispersion of MOPs, while gas adsorption measurements verify the preservation of the MOP cavities within the PLs. Gas uptake follows a diffusion-controlled process with delayed equilibration, and broadband dielectric spectroscopy quantitatively links PDMS segmental dynamics to gas transport, revealing the critical role of grafted chains. By further tuning the grafting density of PDMS on MOPs and the molecular weight of the PDMS melts, the impact of MOP dispersion and matrix size on the gas sorption of PLs is confirmed. Meanwhile, the PL's adsorption capability toward different gas molecules is studied for emergent application in adsorption-based gas separation.