Structural diversity in a series of metal–organic frameworks (MOFs) composed of divalent transition metals, 4,4′-bipyridine and a flexible carboxylic acidElectronic supplementary information (ESI) available: Synthesis procedures, single-crystal X-ray data collection, structure solution and refinement procedures, thermal stability MOFs reported in this paper. CCDC reference numbers 760834–760838. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c000723d

A series of flexible metal–organic frameworks (MOFs) have been successfully synthesized under hydrothermal condition using 1,3-adamantanediacetic acid (C14H20O4, H2ADA) as a flexible dicarboxylate building block, 4,4′-bipyridine and transition metal ions [Cd(ii), Zn(ii), and Mn(ii)] as metal centers in DMF and aqueous media. These MOFs formulated as [Cd(ADA)(4,4′-bipy)0.5]·(DMF) (Cd-ADA-1), [Mn(ADA)(4,4′-bipy)0.5]·(DMF) (Mn-ADA-1), Zn(ADA)(4,4′-bipy)0.5(Zn-ADA-1), and [Mn(HADA)2(4,4′-bipy)(H2O)2] (Mn-ADA-2) (ADA = 1,3-adamantanediacetate, 4,4′-bipy = 4,4′-bipyridine and DMF = N,N′-dimethyl formamide) display interesting 1D, 2D and 3D structural features depending on the solvent of synthesis. All these MOFs were structurally determined by single-crystal X-ray diffraction. The coordination modes of this ligand are discussed and in addition, thermal stability and hydrogen (H2) and carbon-dioxide (CO2) adsorption properties of Cd-ADA-1, Mn-ADA-1and Zn-ADA-1are also presented. Hydrogen sorption at 77 K and up to 1 atm is found to be 0.42, 0.72 and 1.36 wt% without saturation for Zn-ADA-1, Mn-ADA-1and Cd-ADA-1samples. [ABSTRACT FROM AUTHOR]