Recent advances of CO2-responsive materials in separations

Abstract

Separation is widely involved in many fields, such as materials synthesis, gas purification or removal, water treatment, petroleum exploitation, soil remediation, food and medicine production, etc. Compared with the physical separation, the chemical separation has unique advantages when the functionalized process aids are added in systems. The CO2-responsive materials are considered as promising separating mediums due to their relatively green and easily recyclable properties, which realize the resource utilization of CO2. Up to date, the reported CO2-responsive materials are mainly referred to switchable-hydrophilicity solvents, switchable surfactants, switchable water additives, switchable ionic liquids and CO2-responsive polymers. These CO2-responsive materials can be switched by CO2 trigger at moderate conditions, showing switchable properties, such as hydrophilicity-hydrophobicity conversion, switching “on” or “off” surface-activity and switchable change in ionic strength. These switchable properties can be applied in separations, especially in oil-solid separation, oil-water separation, wastewater treatment and acid gas capture. In this review, the recent advances of CO2-responsive materials in separation fields above have been overviewed. Additionally, the present challenges and future engineering considerations have been touched to provide potential insights and theoretical fundamentals for developing CO2-responsive materials.