# Ionic Liquids Hybridization for Carbon Dioxide Capture: A Review
## 4 Application of ILs Hybrid Material in Carbon Dioxide
### ILs/Cellulose
Their study mainly focuses on combination of cellulose with 5-50 wt% solid [N\({}_{444}\)][Oac] due to its easy handling, high water tolerance and effectively coating cellulose. In this work, the hybrid sorbent was prepared by dissolving ILs in solution containing equal ratio of methanol and isopropanol. Then, cellulose was added into the mixture and solvent was removed under vacuum resulting in coated cellulose. As the capacity increased linearly with rising pressure, a noticeable enhancement in CO\({}_{2}\) uptake capacity was observed at a pressure of 10 bar for the 25:75 weight ratio of [N\({}_{444}\)][Oac]: cellulose. At 30 bar, the CO\({}_{2}\) uptake capacity reached up to 3.16 wt% which is about 8.5 times higher than pure ILs. Morphological analysis revealed the presence of surface roughness which was induced by the presence of [N\({}_{444}\)][Oac] in hybrid sorbent, thus creating a pseudo-microporous structure that can provide CO\({}_{2}\) binding sites. This assists in improving CO\({}_{2}\) capture capacity as observed in [N\({}_{444}\)][Oac]/cellulose. However, the uptake capacity was gradually decreased starting from 80 to 95 wt% of cellulose loading which could possibly be due to incomplete [N\({}_{444}\)][Oac] coverage on cellulose surface, thus leading to a smaller CO\({}_{2}\) capture area. The study on CO\({}_{2}\) capture was extended to [N\({}_{1888}\)][Oac]/cellulose, [N\({}_{888}\)][Br]/cellulose and [Bmim][Br]/cellulose. For example, pure [N\({}_{888}\)][Br] had the lowest CO\({}_{2}\) uptake of 0.71 wt%, whereas [N\({}_{888}\)][Br]: cellulose (30:70) exhibited a significant improvement with a CO\({}_{2}\) capacity of 1.98 wt%. The coating of ILs onto cellulose resulted in an improvement of CO\({}_{2}\) capture compared to pure ILs. Despite the fact that [N\({}_{1888}\)][Oac]/cellulose exhibited an enhancement in surface area, the crucial factor in CO\({}_{2}\) capture is believed to be the surface properties, given the slight increase observed in comparison to pure [N\({}_{1888}\)][Oac]. In the meantime, additional study on adsorption and desorption showed the sorbent is highly stable while simultaneously maintaining the CO\({}_{2}\) uptake capacity. Another study tailored the physiochemical properties of chitosan-aerogel with several poly-ILs (PILs), namely, P[DADMA][Cl], P[DADMA][OAc], P[VBA][Cl] and P[VBMPyr][Cl] [118]. This combination produces a material known as AEROPIL which will be used for CO\({}_{2}\) capture. In their work, two types of AEROPIL, with and without glutaraldehyde, were prepared by the sol-gel method. Chitosan was initially dissolved in water containing 1.0% (\(v\)/\(v\)) acetic acid. A solution of PILs was incorporated into the gel solution subjected to the concentration of chitosan and glutaraldehyde. The mixture was transferred into a plastic syringe and slowly dropped in gelation bath (1.0 mol/L NaOH) solution at flow rate 0.65 mL/min. The hydrogel beads were allowed to remain in the gelation bath for 24 h, after which the solution was replaced with ethanol to remove any remaining water traces. The alcogel particles were then collected and placed in an autoclave in which the solvent was removed by using supercritical extraction method under controlled pressure and temperature. FTIR and \({}^{13}\)C solid NMR confirmed the successful of PILs incorporation into chitosan aerogel. The analysis of the textural characteristics showed that AEROPIL-15%P[DADMA][OAc] and AEROPIL-15%P[DADMA][Cl] have higher specific surface area and pore volume than the pure chitosan aerogel (CHT). This is probably due to hydrophilic properties of P[DADMA] ILs which allow better affinity towards chitosan. Conversely, the AEROPILs that were modified with vinylbenzyl PILs experienced the opposite effect. The CO\({}_{2}\) capture was conducted by using thermogravimetric analyzer (TGA) in which the test was performed under ambient conditions. The incorporation of 30% P[DADMA][Cl] into AEROPIL resulted in a CO\({}_{2}\) capacity of 0.70 mmol/g after just 10 min of exposure time.