Amino-functionalized ZIFs-based porous liquids with low viscosity for efficient low-pressure CO₂ capture and CO₂/N₂ separation

Construct permanent porosity into liquids remains challenging, such as preparation, lower viscosity, economical, high-performance gas sorption, and separation. Herein, a general and economical surface engineering strategy has been implemented to construct a novel type Ⅰ porous liquids based on zeolitic imidazolate frameworks (denoted as ZIFs-based PLs) via covalently linking of amino-functionalized ZIFs with the diglycidyl ether-terminated of PDMS. The properties including free pore volume, viscosity, melting temperature (T_m), the gas capture, and CO₂/N₂ selective separation performance of PLs can be regulated by adjusting the pore structures, the amount of –NH₂ introduced into ZIFs and molecular weight of the outer layers of PDMS, etc. Particularly, PLs1(1000)-5%, and PLs2(1000)-5% present viscosity values with 49 mPa⋅S^-1 and 59 mPa⋅S^-1 at 25 °C, to our best knowledge, which is the lowest viscosity of type I PLs reported previously. Meanwhile, T_m of PLs broke down to −78 °C, showing a wide liquid range. Remarkably, type Ⅰ PLs1(14000)-15.5% exhibits approximately 10 times higher CO₂ uptake than that of the polymer in outer layers, which is attributed to the permanent free volume of ZIFs, chemistry sorption, and excellent liquidity. The CO₂ breakthrough time of PLs for the CO₂/N₂ mixture was delayed for 53.7 s, confirming that PLs exhibits efficient CO₂/N₂ separation performance. Therefore, we envision that such a general and economical strategy will open new insights to construct innovative low viscosity type Ⅰ PLs with high-performance CO₂ capture and CO₂/N₂ separation at low pressure.