K. L. Gurunatha

Temperature- and stoichiometry-controlled dimensionality in a magnesium 4,5-imidazoledicarboxylate system with strong hydrophilic pore surfaces.

1D, 2D, and 3D three metal-organic hybrid frameworks of Mg (II) have been synthesized using 4,5-imidazoledicarboxylic acid (H 3idc) with control of the temperature and stoichiometry in a hydrothermal technique. All of the frameworks show high thermal stability, and frameworks 1D and 3D provide highly hydrophilic pore surfaces, correlated by the selective sorption of water molecules over the organic vapor and other gases like N 2 and CO 2.

Versatile functionalities in MOFs assembled from the same building units: interplay of structural flexibility, rigidity and regularity

A systematic study of the formation of Cu(II) metal–organic frameworks (MOFs) with 1,4-naphthalene dicarboxylate (1,4-ndc) was carried out by varying solvent and temperature that resulted four new MOFs {[Cu(1,4-ndc)·H2O·3H2O} (1), {[Cu(1,4-ndc)(MeOH)]·MeOH} (2), {[Cu(1,4-ndc)(H2O)]·1.8H2O} (3) and {[Cu2(μ-OH)2(1,4-ndc)](H2O)} (4). Single crystal structural analyses reveal that a paddle-wheel Cu2(CO2)4 core is the secondary building unit in 1–3 and extended to different dimensionality by the 1,4-ndc ligand. Compound 1 shows a unique 2-fold interpenetrated 3D biporous structure with hydrophobic and hydrophilic channels. Compounds 2 and 3 have 2D networks with different orientations of the 1,4-ndc ligand and provide a 1D supramolecular channel structure. Compound 4 was characterized by IR, CHN, PXRD and FESEM analyses. All the frameworks show permanent porosity suggested by the CO2 sorption studies. Dehydrated frameworks of 1 and 4 exhibit gas storage properties whereas 2 shows highly selective gated MeOH sorption over H2O. Compound 4 shows ferromagnetic ordering, suggesting coexistence of multiple functionalities within the same framework. Overall, we have fabricated MOFs with adaptable functionalities supported by structural regularities based on the same building units.

Guest-Induced Irreversible Sliding in a Flexible 2D Rectangular Grid with Selective Sorption Characteristics

A 2D noninterpenetrated flexible metal-organic porous solid, {[Cu(2)(cis-chdc)(2)(bpee)] x H(2)O}(n) (1) based on a paddle-wheel building unit has been constructed using a mixed-ligand system. Guest-induced irreversible internetwork displacements of the 2D grids result in permanent porosity in the framework, as realized by the selective CO(2) sorption over N(2). The different affinity and selectivity of the solvent molecules was correlated with the internal polarity of the pore surfaces.

Construction of bi-functional inorganic–organic hybrid nanocomposites

Single system bi-functional inorganic–organic hybrid nanocomposites, PB@SiO2@BTC@Ln (PB = Prussian blue, BTC = benzene tricarboxylate; Ln = Tb(III)/Sm(III)) having a PB magnetic core and a luminescent lanthanide probe, show superparamagnetic behavior and significant enhancement in luminescence intensities.

1D chains, 2D networks and 3D interdigitated frameworks of isoorotic acid or 4,4′-bipyridyl and isoorotic acid: syntheses, structures, and sorption properties

Five new coordination polymers, {[Cu(H2iso)2]·2H2O}n (1), {Mn(Hiso)(H2O)3}n (2), {Mn(Hiso)(H2O)2}n (3), {[Cu(Hiso)(4,4′-bipy)(H2O)]·2H2O}n (4) and {[Ni(Hiso)(4,4′-bipy)(H2O)}]·0.5(4,4′-bipy)}n (5) (H3iso = 2,4-dihydroxypyrimidine-5-carboxylic acid or isoorotic acid; 4,4′-bipy = 4,4′-bipyridyl), have been synthesized using hydrothermal as well as room temperature solvent diffusion techniques and structurally characterized. Compounds 1 and 2 are 1D coordination polymers which are further connected by O–H⋯N, O–H⋯O hydrogen bonding interactions forming 3D supramolecular frameworks. Compound 3 is a 2D coordination polymer where 1D chains of {Mn(Hiso)(H2O)2} are linked by an oxo (μ2-O) bridge. Compound 4 consists of isoorotic acid and 4,4′-bipy, a mixed linker system. It forms a 2D sheet like extended structure and these sheets stack on each other to give a 3D supramolecular porous structure. In case of 5, Ni(Hiso) 1D chains are bridged by 4,4′-bipy forming a 2D network and networks are further interdigitated through hydrogen bonding interactions resulting in a 3D supramolecular framework with a 1D channel where 4,4′-bipy molecules are accommodated as guests. Compound 5 undergoes a structural contraction after the removal of the guest 4,4′-bipy and metal bound water molecules and shows a non-porous behaviour toward N2 at 77 K. However, at 195 K, it shows a stepwise uptake for both CO2 and C2H2, suggesting the flexible nature and polar pore surface of the framework.