Reversible transformation of ZnII coordination geometry in a single crystal of porous metal-organic framework [Zn3(ntb)2(EtOH)2]•4 EtOH

A 3D porous metal-organic framework [Zn-3(ntb)(2)(EtOH)(2)](n)center dot 4nEtOH (1) that generates 1D channels of honeycomb aperture has been prepared by the solvothermal reaction of Zn(NO3)(2)center dot 6H(2)O and 4,4',4"-nitrilotrisbenzoic acid (H3NTB) in EtOH at 110 degrees C. Framework 1 exhibits reversible single-crystal-to-single-crystal transformations upon removal and rebinding of the coordinating EtOH as well as the EtOH guest molecules, which give rise to desolvated crystal [Zn-3(ntb)(2)](n) (1') and resolvated crystal [Zn-3(ntb)(2)(EtOH)(2)](n)center dot 4nEtOH (1"). The X-ray structures indicate that 3D host framework is retained during the transformations from 1 to 1' and from 1' to 1", but the coordination geometry of Zn-II ions changes from/to trigonal bipyramid to/ from tetrahedron, concomitant with the rotational rearrangement of a carboxylate plane of the NTB3- relative to its associated phenyl ring. To retain the single crystal integrity, extensive cooperative motions must exist between the molecular components throughout the crystal. Framework V exhibits permanent porosity, thermal stability up to 400 degrees C, and blue luminescence, and high storage capabilities for N-2, H-2, CO2, and CH4.