CO₂ and CH₄ Sorption by Solid-State [P_{4 4 4 4}][NTf₂] Ionic Liquid Based on Quartz Crystal Microbalance Experiments under Different Pressures

Using a quartz crystal microbalance (QCM) measurement system, CO2 and CH4 capacity trapped by a solid-state ionic liquid, tetrabutylphosphonium bis(trifluoromethanesulfonyl)imide [P4 4 4 4][NTf2], which was coated on the surface of a quartz crystal under pressures from 0.1 to 3 MPa at 30 °C, was calculated on the basis of the Sauerbrey equation. The frequency data under the pressure of 4 MPa are not applicable for CO2 measurements, because the...