Computational design of hybrid frameworks: Structure and energetics of two Me3OF3{-O2C-C6H4-CO2-}(3) metal-dicarboxylate polymorphs, MIL-hypo-1 and MIL-hypo-2

The present paper aims at exploring the candidate hybrid structures of the Cr/trimesic acid system by assembling pre-defined hybrid building-blocks in direct space. Two possible hybrid building-blocks were identified where the connection of the 1,4 BDC molecules to an inorganic metal-containing trimer forms a large supertetrahedron (ST) or alternatively a large supercube (SC). From existing topologies derived from the space filling packing of corner-sharing cubes and tetrahedra, two candidates hybrid crystal structures were constructed. Lattice energy minimizations were performed on each candidate structure, as a preliminary step towards the estimation of their relative stabilities. This work further illustrates the computational design of very open hybrid frameworks using the concept of pre-defined building blocks and their assembly in 3D space.