Ab lnitio Study of the Adsorption of Small Molecules on Metal-Organic Frameworks with Oxo-centered Trimetallic Building Units: The Role of the Undercoordinated Metal Ion

The interactions of H-2, CO, CO2, and H2O with the under-coordinated metal centers of the trimetallic oxo-centered M-3(III)(mu(3)-O)(X) (COO)(6) moiety are studied by means of wave function and density functional theory. This trimetallic oxo-centered cluster is a common building unit in several metal organic frameworks (MOFs) such as MIL-100, MIL-101, and MIL-127 (also referred to as soc-MOF). A combinatorial computational screening is performed for a large variety of trimetallic oxo-centered units (M3O)-O-III (M = Al3+, Sc3+, V3+, Cr3+, Fe3+, Ga3+, Rh, In3+, Ir3+) interacting with H2O, H-2, CO, and CO2. The screening addresses interaction energies, adsorption enthalpies, and vibrational in properties. The results show that the Rh and Ir analogues are very promising so materials for gas storage and separations.