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Hydrothermal reactions of N-auxiliary flexible exo-bidentate ligand 1,3-bis(4-pyridyl)propane (bpp) and carboxylates ligands naphthalene-2,6-dicarboxylic acid (2,6-H2ndc) or 4,4′-(hydroxymethylene)dibenzoic acid (H2hmdb), in the presence of cadmium(II) salts have given rise to two novel metal-organic frameworks based on flexible ligands (FL-MOFs), namely, [Cd2(2,6-ndc)2(bpp)(DMF)]·2DMF (1) and [Cd3(hmdb)3(bpp)]·2DMF·2EtOH (2) (DMF=N,N-Dimethylformamide). Single-crystal X-ray diffraction analyses revealed that compound 1 exhibits a three-dimensional self-penetrating 6-connected framework based on dinuclear cluster second building unit. Compound 2 displays an infinite three-dimensional ‘Lucky Clover’ shape (2,10)-connected network based on the trinuclear cluster and V-shaped organic linkers. The flexible bpp ligand displays different conformations in 1 and 2, which are successfully controlled by size-matching mixed ligands during the self-assembly process.

A new multifunctional enantiopure ligand, (S)-2-(1,8-naphthalimido)-3-(4-imidazole)propanoate (s-nip), containing a homochiral center derived from l-histidine and a strong π···π stacking 1,8-naphthalimide synthon, has been used to prepare three novel metal–organic frameworks. The frameworks of [Zn(s-nip)2]n (1) and {[Co(s-nip)2]·(H2O)0.5}n (2) are isostructural three-dimensional (3D) homochiral supramolecular structures organized one-dimensional (1D) ribbons by strong hydrogen bonds and π···π interactions, which display ferroelectric behavior at room temperature. The complex [Cu(nia)2·(H2O)5]n (3) was constructed under a hydrothermal in situ ligand synthesis reaction, in which the new ligand 2-(1,8-naphthalimido)-3-(4-imidazole)acrylate (nia) was formed from the s-nip ligand via a dehydrogenation reaction. The two-dimensional network of 3 stacks into a 3D structure via π···π interactions resulting in 1D hydrophilic channels.

Two isomorphic 2D metal–organic coordination polymers, [Zn(bpndc)(H2O)]∞ (1) and [Cd(bpndc)(H2O)]∞ (2), have been hydrothermally prepared by exploring a semi-rigid V-type dicarboxylate ligand, benzophenone-4,4′-dicarboxylic acid (H2bpndc). Two complexes were characterized by single crystal X-ray diffraction, elemental analyses, IR spectrum, powder X-ray diffraction, thermal analyses, UV–Vis and fluorescence emission spectra. The metal ions in 1 and 2 are connected by carboxylate groups of bpndc to generate a 1D chain with doubly helical structures. The chains are linked by bpndc to form a 2D sinusoidal wavelike layer, which are further assembled with O–H⋯O hydrogen bonds to generate a 3D supramoleclar networks. The topology of 2D structure is an unusual flat (3,4)-connected net forming 4 and 6-gons with the Schlafli notation of (4·62)(42·62) (see Natarajan and Mahata, 2009 [14]).

Two 3D noninterpenetrated pillar-layered metal–organic frameworks have been synthesized under solvothermal reactions based on a N,N′-di(4-pyridyl)-1,4,5,8-naphthalenetetracarboxydiimide (DPNDI) pillar. Single-crystal X-ray diffraction analyses revealed that compound [Co3(BDC)3(DPNDI)(DMF)2]·2CH3CN (1) displays an eight-connected hex net with Schlafli symbol 36·418·53·6 and consists of a DPNDI pillar and 2D 36 net layer that was constructed from a pinwheel trimetallic secondary building unit and 1,4-benzenedicarboxylate (BDC) linker. Compound [Zn2(HFIPBB)2(DPNDI)]·8DMF (2) exhibits a six-connected mab net with Schlafli symbol 44·610·8 and consists of a DPNDI pillar and 2D wavelike 44 net layer with helical channels that was constructed from a paddlewheel dimetallic secondary building unit and bent V-type 4,4′-(hexafluoroisopropylidene)bis(benzoate) linker. The phase purity, thermal stability, and N2 adsorption/desorption of 1 and 2 were measured; the antiferromagnetic property of 1 as well as the photochro...

Two novel Mg-based metal–organic framework isomers with the formula [Mg2(HCO2)2(NH2-BDC)(DMF)2]n (NH2-BDC = 2-amino-1,4-benzenedicarboxylate) have been synthesized based on a 6-connected [24-MC-6] metallacrown secondary building unit (SBU), which display a two-dimensional (2D) 36 net (1) and three-dimensional primitive rhombohedral net (2) derived from a different extended orientation of SBU, respectively. The 2D framework of 1 exhibits relevant thermal stability, solvents stability, high CO2 adsorption, and strong luminescent properties.