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

Abstract

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 (Tm), 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, Tm 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.