Enhanced CO₂ Capture and Separation with Amino Poly(carboxylic acid) Ionic Liquids@MIL-101: Tailored Functionality for Superior Performance

Ionic liquids integrated with metal–organic frameworks (ILs@MOFs) represent a new class of porous materials that combine the structural porosity of MOFs with the selective absorption properties of ILs. These materials have significant potential in CO2 capture and separation, which have garnered significant attention. In this study, amino polycarboxylate ILs ([P4442]n[X]@MIL-101, X represented as [GLY]−, [IDA]2–, and [NTA]3–) were incorporated in MIL-101 by the impregnation method. The synthesis process and detailed characterizations of synthesized [P4442]2[IDA]/ZIF-8, along with the impact of varying [P4442]2[IDA] loading amounts on the CO2 separation performance, were investigated. In particular, [P4442]2[IDA]@MIL-101 (49 cm3 g–1) exhibited a 23% increase compared to MIL-101, with a CO2/N2 selectivity that was 100 times greater than that of MIL-101 at 298 K and 100 kPa. The material also showed a high CO2 adsorption enthalpy, indicating the presence of a strong interaction between [P4442]2[IDA]@MIL-101 and CO2. Additionally, the CO2 uptake and [P4442]2[IDA]@MIL-101 remained stable after 20 adsorption–desorption cycles. Fixed-bed adsorption experiments further revealed that [P4442]2[IDA]@MIL-101 possesses the ability to obtain a high purity of CO2 (99.9%) from a CO2/N2 mixture. This study could facilitate the rational design of ILs@MOFs with tailored functionalities for enhanced gas separation applications.