466692 Using Adsorption Calorimetry to Evaluate the Adsorption Properties in Porous Materials
The present study aims to highlight the continuing interest of adsorption microcalorimetry for the characterization of adsorbate-adsorbent interactions, such as Metal Organic Frameworks materials with various gases. There is a growing interest on “Metal Organic Frameworks” (MOFs) in many areas dealing with porous materials. These hybrid solids are formed of metallic centres linked to each other through organic chains. Along with their flexibility, one of the most interesting structural features in some MOFs is their open metal centres (or coordinatively unsaturated sites). These open metal centres play a strong role as specific sites for gas adsorption. The ability to modulate the strength of the gas-MOF interaction by changing the metal centre is of interest for possible applications in the separation of mixtures where specific interactions may well be necessary. These include propane/propene and CO2/N2.
Two well-known MOF structures with open metal sites are considered: MIL-100(M) and M2(dobdc). In the case of MIL-100, the Al, Fe, Cr and V forms are considered whereas for the M2(dobdc) the Fe, Mn, Zn, Co and Ni forms are studied. The adsorption enthalpies are measured at 77 K, for H2, N2, Ar, CO, CH4, and at 303 K, for N2, CO, CO2, CH4, C2H6, C3H6, C3H8 and C4H10. All of this data allows a number of trends to be made including the role of gas polarizability and that of the metal electronegativity.