MOFs, Cu-BTC, MIL-101, virial-Langmuir, dual site Langmuir
Here, we present a comparative study on gas adsorption of CO, CO2 and CH4 on two of the most versatile MOFs reported till date: Cu-BTC (or, HKUST-1) and MIL-101 (or, Cr-BDC). The high pressure (0-100 bar) pure gas adsorption studies were carried out gravimetrically (Rubotherm, Magnetic Suspension Balance) at varying temperatures. Virial-Langmuir and Dual Site Langmuir models were found to suitable in explaining the experimental isotherm data on Cu-BTC and MIL-101 respectively. Many significant thermodynamic parameter values (Henry’s constant, Enthalpy of adsorption) were evaluated from the pure component isotherm studies, showing electrical properties of the probe molecules (viz. dipole moment, quadrupole moment, polarizability) as well as the nature of the adsorbent surface directly influencing the adsorption. Additionally, the isotherm curves of all three probe molecules show a very interesting cross-over feature, independent of temperature.