An electrostatic repulsion strategy construct ZIFs based liquids with permanent porosity for efficient CO₂ capture

Porous liquids (PLs), as a novel liquid sorbent with permanent porosity, still present challenges such as high viscosity and melting temperatures. Herein, an efficient electrostatic repulsion strategy is proposed to engineer zeolitic imidazolate frameworks (ZIFs) type III PLs employing ZIF-8-g-BPEI nanoparticle stability dispersed into BPEI. The viscosity and melting temperatures of ZIF-8-g-BPEI PLs could be tailored via control particle size, grafting polymer, and concentration of porous nanoparticles. The existence of BPEI on the surface of ZIF-8-g-BPEI facilitates the stable dispersion of ZIFs nanoparticles in BPEI via the electrostatic repulsion as well as enhances CO₂ adsorption capacity of PLs. Moreover, the CO₂ adsorption amount of ZIF-8-g-BPEI-30 PLs is 6.5 times high than that of neat BPEI, suggesting the permanent free volume of ZIFs is retained in their corresponding PLs. Benefiting from the branched structure of BPEI grafted onto the outer surface of ZIFs, ZIF-8-g-BPEI-10 PLs remain liquified down to -71.1 °C, together with viscosity as 1.7 Pa·s⁻¹ at 25 °C. Therefore, the electrostatic repulsion strategy opens an effective avenue to prepare novel liquid materials and shows numerous potential applications in gas adsorption and separation.