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We report the design and synthesis of an amide functionalized microporous organic polymer (Am-MOP) prepared from trimesic acid and p-phenylenediamine using thionyl chloride as a reagent. Polar amide (-CONH-) functional groups act as a linking unit between the node and spacer and constitute the pore wall of the continuous polymeric network. The strong covalent bonds between the building blocks (trimesic acid and p-phenylenediamine) through amide bond linkages provide high thermal and chemical stability to Am-MOP. The presence of a highly polar pore surface allows selective CO2 uptake at 195 K over other gases such as N2, Ar, and O2. The CO2 molecule interacts with amide functional groups via Lewis acid-base type interactions as demonstrated through DFT calculations. Furthermore, for the first time Am-MOP with basic functional groups has been exploited for the Knoevenagel condensation reaction between aldehydes and active methylene compounds. Availability of a large number of catalytic sites per volume and confined microporosity gives enhanced catalytic efficiency and high selectivity for small substrate molecules.

We report the synthesis, structural characterization, and porous properties of two isomeric supramolecular complexes of ([Cd(NH2 bdc)(bphz)0.5 ]⋅DMF⋅H2 O}n (NH2 bdc=2-aminobenzenedicarboxylic acid, bphz=1,2-bis(4-pyridylmethylene)hydrazine) composed of a mixed-ligand system. The first isomer, with a paddle-wheel-type Cd2 (COO)4 secondary building unit (SBU), is flexible in nature, whereas the other isomer has a rigid framework based on a μ-oxo-bridged Cd2 (μ-OCO)2 SBU. Both frameworks are two-fold interpenetrated and the pore surface is decorated with pendant -NH2 and NN functional groups. Both the frameworks are nonporous to N2 , revealed by the type II adsorption profiles. However, at 195 K, the first isomer shows an unusual double-step hysteretic CO2 adsorption profile, whereas the second isomer shows a typical type I CO2 profile. Moreover, at 195 K, both frameworks show excellent selectivity for CO2 among other gases (N2 , O2 , H2 , and Ar), which has been correlated to the specific interaction of CO2 with the -NH2 and NN functionalized pore surface. DFT calculations for the oxo-bridged isomer unveiled that the -NH2 group is the primary binding site for CO2 . The high heat of CO2 adsorption (ΔHads =37.7 kJ mol(-1) ) in the oxo-bridged isomer is realized by NH2 ⋅⋅⋅CO2 /aromatic π⋅⋅⋅CO2 and cooperative CO2 ⋅⋅⋅CO2 interactions. Further, postsynthetic modification of the -NH2 group into -NHCOCH3 in the second isomer leads to a reduced CO2 uptake with lower binding energy, which establishes the critical role of the -NH2 group for CO2 capture. The presence of basic -NH2 sites in the oxo-bridged isomer was further exploited for efficient catalytic activity in a Knoevenagel condensation reaction., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report the design and synthesis of two porous graphene frameworks (PGFs) prepared via covalent functionalization of reduced graphene oxide (RGO) with iodobenzene followed by a C-C coupling reaction. In contrast to RGO, these 3D frameworks show high surface area (BET, 825 m(2) g(-1)) and pore volumes due to the effect of pillaring. Interestingly, both the frameworks show high CO2 uptake (112 wt% for PGF-1 and 60 wt% for PGF-2 at 195 K up to 1 atm). PGFs show nearly 1.2 wt% H2 storage capacity at 77 K and 1 atm, increasing to ∼1.9 wt% at high pressure. These all carbon-based porous solids based on pillared graphene frameworks suggest the possibility of designing related several such novel materials with attractive properties.

We report the synthesis, structural characterization and adsorption properties of three new porous coordination polymers {[Cu(Meazpy)0.5(glut)](H2O)}n (2), {[Zn(azpy)0.5(terep)](H2O)}n (3), and {[Zn(Meazpy)0.5(terep)]}n (4) [glut = glutarate, terep = terephthalate, azpy = N,N'-bis-(pyridin-4-ylmethylene)hydrazine and Meazpy = N,N'-bis-(1-pyridin-4-ylethylidene)hydrazine] composed of mixed linkers systems. Structure determination reveals that all three compounds have three-dimensional (3D) coordination frameworks bridged by dicarboxylates and Schiff base linkers. In all cases 2D dicarboxylate layers are supported by paddle-wheel M2(CO2)4 SBUs extended in three dimensions by designed Schiff base linkers. Compound 1, which has been reported in a paper earlier by our group, is a robust porous three-dimensional (3D) framework whose pore surface was found to be decorated with the -CH=N- groups of a linear Schiff base (azpy) and it showed reversible single-crystal-to-single-crystal transformation and selective CO2 uptake. By using another linear Schiff base linker Meazpy, we have synthesized compound 2 which is isostructural with 1, having an additional methyl group pointing towards the pore. Like 1 it also shows a reversible single-crystal-to-single-crystal transformation upon dehydration and rehydration. The dehydrated framework of 2 exhibits 50% enhanced CO2 uptake compared to 1. This has been achieved by the pore surface modification effected upon changing the pillar backbone from a -CH=N- to -CMe=N- group. It also adsorbs water vapour at 298 K. In the case of the two isostructural 3D MOFs 3and 4, the use of a rigid carboxylate (terephthalate) linker arrested porosity by three-fold interpenetration. We showed that the use of aliphatic dicarboxylate (glutarate) results in a non-interpenetrated framework rather than the common interpenetrated framework with aromatic dicarboxylates in mixed ligand systems.

Here we have used Raman spectroscopy to investigate molecular level changes in the zeolitic imidazolate framework ZIF-8 (a prototypical zeolite-like porous metal organic framework) as a function of temperature. Temperature dependent Raman spectra suggest that at low temperature the softening of the C-H stretching frequencies is due to the decrease in steric hindrance between the methyl groups of methyl imidazole. The larger separation between the methyl groups opens the window for increased nitrogen and methane uptake at temperatures below 153 K. The appearance of Raman bands at 2323 cm(-1) and 2904 cm(-1) at or below 153 K in ZIF-8 are characteristic signatures of the adsorbed nitrogen and methane gases respectively. Nanoscale ZIF-8 uptakes more molecules than bulk ZIF-8, and as a result we could provide evidence for encaged CO2 at 203 K yielding its Raman mode at 1379 cm(-1).

We report the synthesis, single-crystal structural characterization, and selective gas adsorption properties of three new 3D metal-organic frameworks of Zn(II), {[Zn3(bipy)3(H2O)2][Fe(CN)6]2·2(bipy)·3H2O}n (1), {[Zn3(bipy)][Fe(CN)6]2·(C2H5OH)·H2O}n (2), and {[Zn3(azpy)2(H2O)2][Fe(CN)6]2·4H2O}n (3) (bipy = 4,4'-bipyridyl and azpy = 4,4'-azobipyridyl), bridged by [Fe(CN)6](3-) and exobidentate pyridyl-based linkers. Compounds 1-3 have been successfully isolated by varying the organic linkers (bipy and azpy) and their ratios during the synthesis at RT. Frameworks 1 and 3 feature a biporous-type network. At 195 K, compounds 1-3 selectively adsorb CO2 and completely exclude other small molecules, such as N2, Ar, O2, and CH4. Additionally, we have also tested the CO2 uptake capacity of 1 and 3 at ambient temperatures. By using the isotherms measured at 273 and 293 K, we have calculated the isosteric heat of CO2 adsorption, which turned out to be 35.84 and 35.53 kJ mol(-1) for 1 and 3, respectively. Furthermore, a reasonably high heat of H2 adsorption (7.97 kJ mol(-1) for 1 and 7.73 kJ mol(-1) for 3) at low temperatures suggests strong interaction of H2 molecules with the unsaturated Zn(II) metal sites and as well as with the pore surface. Frameworks 1 and 3 show high selectivity to CO2 over N2 and CH4 at 273 K, as calculated based on the IAST model. The high values of ΔH(CO2) and ΔH(H2) stem from the preferential electrostatic interaction of CO2 with the unsaturated metal sites, pendent nitrogen atoms of [Fe(CN)6](3-), and π-electron cloud of bipyridine aromatic rings as understood from first-principles density functional theory based calculations.

Hybrid nanocomposites of graphene oxide (GO) with ZIF-8 exhibit tunable nanoscale morphology and porosity, both determined by the GO content, coordination modulation being responsible for such properties. These materials also give rise to high CO2 storage capability and can be used as precursors to prepare GO@ZnS nanocomposites.

Two new end-to-end (EE) cyanate bridged 1D coordination polymers of Ni(II) are isolated which contain linear (180°) Ni-N-C and Ni-O-C angles in Ni-NCO-Ni bridges and show ferromagnetic (F) coupling in agreement with the reported theoretical model for linear EE bridges.

We herein report an unusual CO(2) adsorption behavior in a fluoro-functionalized MOF {[Zn(SiF(6))(pyz)(2)]·2MeOH}(n) (1) with a 1D channel system, which is made up of pyrazine and SiF(6)(2-) moieties. Surprisingly, desolvated 1 (1') adsorbs higher amounts of CO(2) at 298 K than at 195 K, which is in contrast to the usual trend. Combined Raman spectroscopic and theoretical studies reveal that slanted pyrazine rings in 1' with an angle of 17.2° with respect to the (200) Zn(II)-Si plane at low temperature block the channel windows and thus reduce the uptake amount.

A three-dimensional (3D) pillared-layer metal-organic framework, [Cd(bipy)(0.5)(Himdc)](DMF)](n) (1), (bipy =4,4'-bipyridine and Himdc = 4,5-imidazoledicarboxylate) has been synthesized and structurally characterized. The highly rigid and stable framework contains a 3D channel structure with highly polar pore surfaces decorated with pendant oxygen atoms of the Himdc linkers. The desolvated framework [Cd(bipy)(0.5)(Himdc)](n) (1') is found to exhibit permanent porosity with high H(2) and CO(2) storage capacities. Two H(2) molecules occluded per unit formula of 1' and the corresponding heat of H(2) adsorption (ΔH(H2)) is about ∼9.0 kJ/mol. The high value of ΔH(H2) stems from the preferential electrostatic interaction of H(2) with the pendent oxygen atoms of Himdc and aromatic bipy linkers as determined from first-principles density functional theory (DFT) based calculations. Similarly, DFT studies indicate CO(2) to preferentially interact electrostatically (C(δ+)···O(δ-)) with the uncoordinated pendent oxygen of Himdc. It also interacts with bipy through C-H···O bonding, thus rationalizing the high heat (ΔH(CO2) ∼ 35.4 kJ/mol) of CO(2) uptake. Our work unveiled that better H(2) or CO(2) storage materials can be developed through the immobilization of reactive hetero atoms (O, N) at the pore surfaces in a metal-organic framework.

Two new 1D coordination polymers, [Cu(3)(μ(3)-OH)(ppk)(3)(μ-N(CN)(2))(OAc)](n) (1) and {[Cu(4)(pdmH)(2)(pdm)(2)(μ(2)-OH)(H(2)O)]·ClO(4)}(n) (2) based on two different blocking ligands phenyl-2-pyridylketoxime (ppk) and pyridine-2,6-dimethanol (pdmH(2)) have been synthesized and were characterized by X-ray single crystal structural analysis. In compound 1, the hydroxido-bridged trinuclear core, {Cu(3)(μ(3)-OH)(ppk)(3)(OAc)}, acts as secondary building units and are connected by the N(CN)(2)(-) anions resulting in a one dimensional (1D) coordination polymer. The 1D coordination chains undergo π-π interactions giving rise to a 3D supramolecular framework. In compound 2, tetrameric [Cu(4)(pdmH)(2)(pdm)(2)(H(2)O)](2+) cores are linked via hydroxido groups forming a zigzag 1D coordination chain where non-coordinated ClO(4)(-) ions are intercalated between the chains. Variable temperature magnetic susceptibility study of suggests that Cu(II) ions in the trinuclear Cu(3)(μ(3)-OH) cores are antiferromagnetically coupled with J = -459.7 cm(-1) and g = 2.11 and the trinuclear cores are further weakly coupled antiferromagnetically (zj' = -5.25 cm(-1)) through the N(CN)(2)(-) bridging ligand. Investigation of the magnetic properties of reveals that Cu(II) ions are coupled antiferromagnetically in the tetranuclear core with J = -27.1 cm(-1) and g = 2.17; the Cu(II)(4) building units are further coupled antiferromagnetically with zj' = -9.65 cm(-1). The experimental magnetic behaviours of 1 and 2 are correlated by first principle DFT calculations which provide a qualitative understanding of the origin of antiferromagnetic interactions in both cases.

Exciting assemblies: A metal-organic self-assembly of pyrenebutyric acid (PBA), 1,10-phenanthroline (o-phen), and Mg(II) shows solid-state fluorescence originating from a 1:1 PBA-o-phen exciplex. This exciplex fluorescence is sensitized by another residual PBA chromophore through an excited-state energy-transfer process. The solvent polarity modulates the self-assembly and the corresponding exciplex as well as the energy transfer, resulting in tunable emission of the hybrid (see figure)., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A swell idea! The guest-responsive reversible swelling and fluorescence enhancement of a dynamic, microporous polymer network is presented. Guest-induced breathing of hydrophobic pores imparts multi-functional properties, such as super-absorbency, phase-selective swelling of oil from water and encapsulation of C(60) (see figure), to this soft micro-porous organic polymer., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A 3D porous Zn(II) metal-organic framework {[Zn(2)(H(2)dht)(dht)(0.5)(azpy)(0.5)(H(2)O)]·4H(2)O} (1; H(2)dht=dihydroxyterphthalate, azpy=4,4'-azobipyridine) has been synthesised by employing 2,5-dihydroxyterephthalic acid (H(4)dht), a multidentate ligand and 4,4'-azobipyridine by solvent-diffusion techniques at room temperature. The as-synthesised framework furnishes two different types of channels: one calyx-shaped along the [001] direction and another rectangle-shaped along the [101] direction occupied by guest water molecules. The dehydrated framework, {[Zn(2)(H(2)dht)(dht)(0.5)(azpy)(0.5)]} (1') provides 52.7% void volume to the total unit-cell volume. The pore surfaces of 1' are decorated with unsaturated Zn(II) sites and pendant hydroxyl groups of H(2)dht linker, thereby resulting in a highly polar pore surface. The dehydrated framework 1' shows highly selective adsorption of CO(2) over other gases, such as N(2), H(2), O(2) and Ar, at 195 K. Photoluminescence studies revealed that compound 1 exhibits green emission (λ(max)≈530 nm) on the basis of the excited-state intramolecular proton-transfer (ESIPT) process of the H(2)dht linker; no emission was observed in dehydrated solid 1'. Such guest-induced on/off emission has been correlated to the structural transformation and concomitant breaking and reforming of the OH···OCO hydrogen-bonding interaction in the H(2)dht linker in 1'/1., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A new 2D pillared-bilayer porous coordination polymer (PCP) has been synthesized and structurally characterized that shows selective adsorption of CO(2) over other gases (N(2), O(2), Ar, H(2), CH(4)) and guest selective single/double-step adsorption of vapor correlated to the successive confinement of adsorbates in a 1D channel and a 2D interlayer space.

The reaction of VOSO(4) with 2-carboxyethylphosphonic acid (H(2)-CEP) in presence of piperazine (PIP) produces a 3D inorganic-organic hybrid framework, {(H(2)PIP)(0.5)[VO(CEP)]·H(2)O} (1) with bidirectional channels occupied by the H(2)PIP cations and H(2)O molecules. The PO(3)(2-) unit of CEP connects three V(IV) centers to generate a 1D ladder, which is further linked to four such ladders by the CEP linkers to form a 3D hybrid framework. The dehydrated framework, {(H(2)PIP)(0.5)[VO(CEP)]} (1') shows selective and gated adsorption behavior with H(2)O but not with methanol and ethanol. Very interestingly, when 1 is treated with an aqueous solution of LiNO(3)/NaNO(3), the framework breaks down and results in a new polyoxovanadate (POV) cluster, [H(5)(H(2)PIP)(3)][V(V)(12)V(IV)(2)O(38)(PO(4))]·8H(2)O (2) at pH ≈ 2.1. The cluster has been characterized by single-crystal X-ray diffraction, (31)P NMR, EPR, and magnetic studies. The temperature-dependent magnetic susceptibility measurement suggests antiferromagnetic ordering in 1 with T(N) ≈ 3.8 K., (© 2011 American Chemical Society)

A bimetallic pillared-layer coordination framework {[Mn(3)(bipy)(3)(H(2)O)(4)][Cr(CN)(6)](2)·2(bipy)·4(H(2)O)}(n) has been constructed using a cyanometallate anion ([Cr(CN)(6)](3-)) and an organic linker (4,4'-bipyridyl) that provides high heat of hydrogen adsorption (∼11.5 kJ mol(-1)) and shows guest dependent magnetic modulation.

CuX(2) (X = ClO(4)(-), NO(3)(-), 0.5 SO(4)(2-), Cl(-)) and 2,3-dihydroxyfumaric acid (dhfa) undergo redox reaction in slightly basic aqueous solution forming Cu(I)X and 2,3-diketosuccinic acid. Pyrazine (pyz) and 1,2-bis(4-pyridyl)ethylene (bpee) linkers have been used for stabilizing and isolating the Cu(I) state in this reaction. The three different Cu(I)-frameworks, {Cu(pyz)(1.5)(ClO(4))}(n) (1), {Cu(pyz)(NO(3))}(n) (2), and {[Cu(bpee)Cl].2H(2)O}(n) (3) with different anions have been synthesized and structurally characterized. The framework topology and dimensionality depends upon the anions. This is a one step synthesis of Cu(I) coordination frameworks with 1 : 2 stoichiometry in relation to dhfa and Cu(II). By controlling the concentration of dhfa, a mixed-valent porous Cu(I)/Cu(II) framework, [Cu(II)Cu(I)(2)(2,4-pyrdc)(2)(pyz)(3)].2H(2)O}(n) (4) has been synthesized and characterized by XPS and magnetic studies. Dehydrated frameworks of 3 and 4 exhibit interesting sorption properties with different solvent molecules. In a similar reaction CuCl(2) and pyz without dhfa produced the corresponding Cu(II)-compound, {Cu(pyz)Cl(2)}(n) (5), suggesting the reducing role of dhfa. Therefore by this simple reaction, it is possible to control the oxidation state as well as the coordination number and geometry of Cu ions. This is a novel synthetic methodology for the stabilization of the Cu +1 state in aqueous solution and open atmosphere.

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.

The reaction of Cu(ClO4)(2).6H2O and 1,2-bis(4-pyridyl)ethane (bpe) in basic aqueous solution yields a 3D compound, {[Cu3(CO3)2(bpe)3].2ClO4}n (1) through the atmospheric fixation of CO2 composing Cu(CO3) kagomé layers pillared by the bpe linker that exhibit weak antiferromagnetic interaction in the kagomé layer and interlayer ferromagnetic coupling at low temperature.

A novel bimetallic [Mn(ii)-Fe(iii)] 3D biporous pillared-layer metal-organic coordination framework constructed by a cyanometallate anion ([Fe(CN)(6)](3-)) and an organic linker (4,4'-bipy) is found to exhibit permanent porosity with excellent size selective vapour sorption properties and H(2)-storage capability.

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.

A metal-organic honeycomb-like 2D pillared-bilayer open framework has been constructed which shows dynamic sponge-like single-crystal-to-single-crystal transformation upon dehydration and rehydration. The dehydrated acentric nonporous phase transformed to the porous centric phase with the selective adsorbate concomitant with the structural transformation correlated with the single-crystal structure determination.

The structure of the title compound, catena-poly[[di-micro-azido-kappa(4)N(1):N(1)-bis[[bis(3-aminopropyl)methylamine-kappa(3)N]copper(II)]]-micro-cyano-[dicyanonickel(II)]-micro-cyano], [Cu(2)(N(3))(2)(medpt)(2)[Ni(CN)(4)]](n) [medpt is bis(3-aminopropyl)methylamine, C(7)H(19)N(2)] or [Cu(2)Ni(CN)(4)(N(3))(2)(C(7)H(19)N(3))(2)](n), is a one-dimensional heterometallic covalent chain where Ni(CN)(4)(2-) functions as a molecular ion bridge. The Ni atom sits on the centre of inversion. The chain undergoes hydrogen-bonding interactions, forming a three-dimensional supramolecular network.

Two polymeric malonato-bridged manganese(II) complexes of formula [Mn(mal)(H(2)O)(2)](n)() (1) and [Mn(2)(mal)(2)(4,4'-bipy)(H(2)O)(2)](n)() (2) have been synthesized and characterized (mal = malonate dianion; 4,4'-bipy = 4,4'-bipyridine). The crystal structure of complex 1 was already known. Complex 2 crystallizes in monoclinic space group P2(1)/n, Z = 2, with unit cell parameters of a = 7.2974(10) A, b = 18.7715(10) A, c = 7.514(3) A, and beta = 91.743(12) degrees. The structure determination reveals that the complex [Mn(2)(mal)(2)(4,4'-bipy)(H(2)O)(2)](n)() (2) is a 3D network being composed of Mn-malonate sheets which are pillared by bidentate 4,4'-bipy spacer forming small voids. The Mn-Mn distances through Mn-mu-(O3-C8-O4)-Mn, Mn-mu(O1-C6-O2)-Mn, and Mn-mu-4,4'-bipy-Mn bridges are 5.561, 5.410, and 11.723 A, respectively. The magnetic behaviors of complexes 1 and 2 in the temperature range 300-2 K are very close, corresponding to a weak antiferromagnetic coupling. The magnetic pathways of complex 1 are through two Mn-O-C-O-Mn with anti-anti conformation and two Mn-O-C-O-Mn with syn-anti conformations and in complex 2 through all Mn-O-C-O-Mn with syn-anti conformations. Both syn-anti and anti-anti conformations create weak antiferromagnetic coupling, and the susceptibility data are fitted by the expansion series of Lines and the Curély formula for an S = 5/2 antiferromagnetic quadratic layer, based on the exchange Hamiltonian H = -Sigma(nn)()JS(i)()S(j)(). The best fit is given by the superexchange parameters J = -0.32 cm(-)(1) and g = 2.00 for complex 1 and J = -0.14 cm(-)(1), J(inter) = -0.031 cm(-)(1), and g = 2.00 for complex 2. Finally, in both the complexes there is a magnetic pathway Mn-O-C-C-C-O-Mn, and this pathway through the three carbon atoms of the malonato-bridging ligand could be considered negligible.