RESUMEN

A family of Cu(II)-based metal-organic frameworks (MOFs) has been synthesized using three pyridyl-isophthalate ligands, H2L1 (4'-(pyridin-4-yl)biphenyl-3,5-dicarboxylic acid), H2L2 (4''-(pyridin-4-yl)-1,1':4',1''-terphenyl-3,5-dicarboxylic acid) and H2L3 (5-[4-(pyridin-4-yl)naphthalen-1-yl]benzene-1,3-dicarboxylic acid). Although in each case the pyridyl-isophthalate ligands adopt the same pseudo-octahedral [Cu2(O2CR)4N2] paddlewheel coordination modes, the resulting frameworks are structurally diverse, particularly in the case of the complex of Cu(II) with H2L3, which leads to three distinct supramolecular isomers, each derived from Kagomé and square nets. In contrast to [Cu(L2)] and the isomers of [Cu(L3)], [Cu(L1)] exhibits permanent porosity. Thus, the gas adsorption properties of [Cu(L1)] were investigated with N2, CO2 and H2, and the material exhibits an isosteric heat of adsorption competitive with leading MOF sorbents for CO2 [Cu(L1)] displays high H2 adsorption, with the density in the pores approaching that of liquid H2This article is part of the themed issue 'Coordination polymers and metal-organic frameworks: materials by design'.

RESUMEN

The selective capture of carbon dioxide in porous materials has potential for the storage and purification of fuel and flue gases. However, adsorption capacities under dynamic conditions are often insufficient for practical applications, and strategies to enhance CO(2)-host selectivity are required. The unique partially interpenetrated metal-organic framework NOTT-202 represents a new class of dynamic material that undergoes pronounced framework phase transition on desolvation. We report temperature-dependent adsorption/desorption hysteresis in desolvated NOTT-202a that responds selectively to CO(2). The CO(2) isotherm shows three steps in the adsorption profile at 195 K, and stepwise filling of pores generated within the observed partially interpenetrated structure has been modelled by grand canonical Monte Carlo simulations. Adsorption of N(2), CH(4), O(2), Ar and H(2) exhibits reversible isotherms without hysteresis under the same conditions, and this allows capture of gases at high pressure, but selectively leaves CO(2) trapped in the nanopores at low pressure.

RESUMEN

Reaction of Co(NO(3))(2)·6H(2)O with H(2)L [H(2)L = pyridine-4-(phenyl-3',5'-dicarboxylic acid)] under different reaction conditions gives three closely-related metal-organic framework polymers, {[Co(2)(L)(2)(DMF)]·n(solv)}(∞) (1), {[Co(L)]·2DMF}(∞) (2) and {[Co(3)(L)(3)(DMF)(0.5)(H(2)O)(1.5)]·n(solv)}(∞) (3). Variation in reaction conditions thus has a decisive impact on the materials isolated, producing frameworks based upon either binuclear (1, 2) or trinuclear (3) cobalt cluster nodes. Analysis of their crystal structures shows that all three contain considerable solvent-accessible volumes, an indication of porosity that is confirmed for desolvated 1 and 3, which can store up to 2.75 and 2.33 wt% of H(2) at 78 K and 20 bar, respectively.

RESUMEN

New ternary and quaternary nitride halides, Ba(2)N(X,X') (X = F, Cl, Br; X' = Br, I), have been synthesized from the high temperature reactions of barium subnitride with the respective barium halides under an inert atmosphere. The former include the first fully characterized barium nitride halides for X other than F, and the latter are the first examples of barium nitride mixed halides. The variation in structure with composition has been investigated by powder X-ray and powder neutron diffraction techniques. The heavier ternary and quaternary nitride halides (X, X' = Cl, Br, I) crystallize in the hexagonal space group R3m, with the anti-α-NaFeO(2) structure. Ba(2)NF forms with both an anti-α-NaFeO(2) structure, in which N(3-) and F(-) are ordered and an anion-disordered simple rock salt structure. The hexagonal polymorph of Ba(2)NF is the only example to date of a nitride fluoride adopting this layered structure. Both the ternary and the quaternary compounds display very weak, temperature independent paramagnetism.

RESUMEN

The metal-organic frameworks NOTT-400 and NOTT-401, based on a binuclear [Sc(2)(µ(2)-OH)(O(2)CR)(4)] building block, have been synthesised and characterised; the desolvated framework NOTT-401a shows a BET surface area of 1514 m(2) g(-1) with a total H(2) uptake of 4.44 wt% at 77 K and 20 bar.

RESUMEN

Two new three-dimensional Sc(III) metal-organic frameworks {[Sc(3)O(L(1))(3)(H(2)O)(3)]·Cl(0.5)(OH)(0.5)(DMF)(4)(H(2)O)(3)}(∞) (1) (H(2)L(1)=1,4-benzene-dicarboxylic acid) and {[Sc(3)O(L(2))(2)(H(2)O)(3)](OH)(H(2)O)(5)(DMF)}(∞) (2) (H(3)L(2)=1,3,5-tris(4-carboxyphenyl)benzene) have been synthesised and characterised. The structures of both 1 and 2 incorporate the trinuclear trigonal planar [Sc(3)(O)(O(2)CR)(6)] building block featuring three Sc(III) centres joined by a central µ(3)-O(2-) donor. Each Sc(III) centre is further bound by four oxygen donors from four different bridging carboxylate anions, and a molecule of water located trans to the µ(3)-O(2-) donor completes the six coordination at the metal centre. Frameworks 1 and 2 show high thermal stability with retention of crystallinity up to 350 °C. The desolvated materials 1a and 2a, in which the solvent has been removed from the pores but with water or hydroxide remaining coordinated to Sc(III), show BET surface areas based upon N(2) uptake of 634 and 1233 m(2) g(-1), respectively, and pore volumes calculated from the maximum N(2) adsorption of 0.25 cm(3) g(-1) and 0.62 cm(3) g(-1), respectively. At 20 bar and 78 K, the H(2) isotherms for desolvated 1a and 2a confirm 2.48 and 1.99 wt% total H(2) uptake, respectively. The isosteric heats of adsorption were estimated to be 5.25 and 2.59 kJ mol(-1) at zero surface coverage for 1a and 2a, respectively. Treatment of 2 with acetone followed by thermal desolvation in vacuo generated free metal coordination sites in a new material 2b. Framework 2b shows an enhanced BET surface area of 1511 m(2) g(-1) and a pore volume of 0.76 cm(3) g(-1), with improved H(2) uptake capacity and a higher heat of H(2) adsorption. At 20 bar, H(2) capacity increases from 1.99 wt% in 2a to 2.64 wt% for 2b, and the H(2) adsorption enthalpy rises markedly from 2.59 to 6.90 kJ mol(-1).

RESUMEN

Reaction of ß-amino-ß-(pyrid-4-yl)acrylonitrile with the aromatic dicarboxaldehydes 9,10-bis(4-formylphenyl)anthracene and terephthalaldehyde affords the dihydropyridyl products 9,10-bis(4-((3,5-dicyano-2,6-dipyridyl)dihydropyridyl)phenyl)anthracene (L(1)) and 1,4-bis(4-(3,5-dicyano-2,6-dipyridyl)dihydropyridyl)benzene (L(2)), respectively. In the solid state [L(1)]·2.5DMF·3MeOH (SOF-1) crystallizes in the monoclinic space group P2(1)/c and forms a 3D stable supramolecular organic framework via strong N-H···N(py) hydrogen bonds and π-π interactions. The material incorporates pyridyl-decorated channels and shows permanent porosity in the solid state. The pore volumes of the desolvated framework SOF-1a calculated from the N(2) isotherm at 125 K and the CO(2) isotherm at 195 K are 0.227 and 0.244 cm(3) g(-1), respectively. The N(2) absorption capacity of SOF-1a at 77 K is very low, with an uptake of 0.63 mmol g(-1) at 1 bar, although saturation N(2) adsorption at 125 K is 6.55 mmol g(-1) (or 143 cm(3) g(-1)). At ambient temperature, SOF-1a shows significant CO(2) adsorption with approximately 3 mol of CO(2) absorbed per mole of host at 16 bar and 298 K, corresponding to 69 cm(3) g(-1) at STP. SOF-1a also adsorbs significant amounts of C(2)H(2), with an uptake of 124 cm(3) (STP) g(-1) (5.52 mmol g(-1)) at 1 bar at 195 K. Methane uptake at 195 K and 1 bar is 69 cm(3) (STP) g(-1). Overall, gas adsorption measurements on desolvated framework SOF-1a reveal not only high capacity uptakes for C(2)H(2) and CO(2), compared to other crystalline molecular organic solids, but also an adsorption selectivity in the order C(2)H(2) > CO(2) > CH(4) > N(2). Overall, C(2)H(2)(270 K)/CH(4)(273 K) selectivity is 33.7 based on Henry's Law constant, while the C(2)H(2)(270 K)/CO(2)(273 K) ratio of uptake at 1 bar is 2.05. The less bulky analogue L(2) crystallizes in the triclinic space group P1 as two different solvates [L(2)]·2DMF·5C(6)H(6) (S2A) and [L(2)]·2DMF·4MeOH (S2B) as pale yellow tablets and blocks, respectively. Each L(2) molecule in S2A participates in two N-H···O hydrogen bonds between dihydropyridyl rings and solvent DMF molecules. Packing of these layers generates 1D nanochannels along the crystallographic a and b axes which host DMF and benzene molecules. In S2B, each L(2) ligand participates in hydrogen bonding via an N-H···O interaction between the N-H of the dihydropyridyl ring and the O of a MeOH and also via an N···H-O interaction between the N center of a pyridine ring and the H-O of a second MeOH molecule. The presence of the L(2)-HOMe hydrogen bonds prevents ligand-ligand hydrogen bonding. As a result, S2B crystallizes as one-dimensional chains rather than as an extended 3D network. Thermal removal of solvents from S2A results in conversion to denser phase S2C which shows no effective permanent porosity.

RESUMEN

We have synthesized five new metal-organic coordination polymers incorporating the bent ligand H(2)hfipbb [4,4'-(hexafluoroisopropylidene)bis(benzoic acid)] with different transition metal ions and co-ligands via solvothermal reactions to give [Zn(2)(hfipbb)(2)(py)(2)] x DMF (1), [Zn(2)(hfipbb)(2)(4,4'-bipy)(H(2)O)] (2), [Zn(2)(hfipbb)(2)(bpdab)].2DMF (3), [Cd(2)(hfipbb)(2)(DMF)(2)] x 2 DMF (4), and [Co(hfipbb)(dpp)] x MeOH (5) (py = pyridine, 4,4'-bipy = 4,4'-bipyridine, bpdab = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, dpp = 1,3-di(4-pyridyl)propane). Compound 1 displays a 2-fold 2D-->2D parallel interpenetrated layer network with one-dimensional (1D) helical channels, while 3 exhibits a three-dimensional pillared helical-layer open framework of alpha-Po topology based upon binuclear paddlewheel units. In compounds 2 and 5, binuclear motifs with double carboxylate bridges are linked by hfipbb(2-) ligands into a 1D ribbon, which are further assembled into two-dimensional non-interpenetrated (4,4) layers via bipyridyl co-ligands. However, the different bridging modes of hfipbb(2-) ligands and the different disposition of the coordinated co-ligands around metal ions result in subtle differences in the final architecture. Thus, 2 is based on a binuclear cluster node, double-stranded hfipbb(2-) linkers, and single-stranded 4,4'-bipy linkers, while 5 is based on a binuclear cluster node and hfipbb(2-) and dpp linkers which are both double-stranded. Among these compounds, the Cd(II) complex 4 is possibly the most interesting because it represents a rare example in which metal centers are linked by carboxylate groups into infinite chains further joined together by hfipbb(2-) spacers to form a 2D network with tubular helical channels. All these coordination polymers exhibit low solvent-accessible volumes. Both 3 and 4 retain structural integrity and permanent microporosity upon evacuation of guest molecules, with hydrogen uptakes of 0.57 and 0.78 wt %, respectively, at 20 bar and 77 K.

Asunto(s)

RESUMEN

Solvothermal reaction of the ligands H(4)L(110) ((2,7-phenanthrenediyl)diisophthalic acid) and H(4)L(111) ([2,7-(9,10-dihydrophenanthrenediyl)]diisophthalic acid) with Cu(NO(3))(2) x 2.5 H(2)O in a slightly acidified mixture of DMF/1,4-dioxane/H(2)O afforded the solvated framework compounds [Cu(2)(L(110))(H(2)O)(2)](DMF)(7.5)(H(2)O)(5) (NOTT-110) and [Cu(2)(L(111))(H(2)O)(2)](DMF)(7.5)(H(2)O)(5) (NOTT-111), respectively. Crystal structure determinations confirmed that NOTT-110 and NOTT-111 have the same NbO framework structure, differing only at the 9 and 10 positions of the phenanthrene group. The BET surface areas for desolvated NOTT-110 and NOTT-111 were estimated to be 2960 and 2930 m(2) g(-1), respectively. Compared with their phenyl analogues, introduction of phenanthrene groups to these porous Cu(II)-carboxylate framework materials leads to an enhancement of H(2) adsorption. Thus, the H(2) isotherms for desolvated NOTT-110 and NOTT-111 confirm 2.64 and 2.56 wt % total H(2) uptake, respectively, at 1 bar and 78 K. NOTT-110 shows a high total H(2) storage capacity of 7.62 wt % at 55 bar and 77 K (8.5 wt % at saturation) with a total volumetric capacity of 46.8 g L(-1) at 55 bar and 77 K.

RESUMEN

The desolvated polyhedral framework material NOTT-112 shows an excess H(2) uptake of 7.07 wt% between 35 and 40 bar at 77 K, and a total H(2) uptake of 10 wt% at 77 bar and 77 K.

Asunto(s)

RESUMEN

A series of isostructural metal-organic framework polymers of composition [Cu2(L)(H2O)2] (L= tetracarboxylate ligands), denoted NOTT-nnn, has been synthesized and characterized. Single crystal X-ray structures confirm the complexes to contain binuclear Cu(II) paddlewheel nodes each bridged by four carboxylate centers to give a NbO-type network of 64.82 topology. These complexes are activated by solvent exchange with acetone coupled to heating cycles under vacuum to afford the desolvated porous materials NOTT-100 to NOTT-109. These incorporate a vacant coordination site at each Cu(II) center and have large pore volumes that contribute to the observed high H2 adsorption. Indeed, NOTT-103 at 77 K and 60 bar shows a very high total H2 adsorption of 77.8 mg g(-)- equivalent to 7.78 wt% [wt% = (weight of adsorbed H2)/(weight of host material)] or 7.22 wt% [wt% = 100(weight of adsorbed H2)/(weight of host material + weight of adsorbed H2)]. Neutron powder diffraction studies on NOTT-101 reveal three adsorption sites for this material: at the exposed Cu(II) coordination site, at the pocket formed by three {Cu2} paddle wheels, and at the cusp of three phenyl rings. Systematic virial analysis of the H2 isotherms suggests that the H2 binding energies at these sites are very similar and the differences are smaller than 1.0 kJ mol-1, although the adsorption enthalpies for H2 at the exposed Cu(II) site are significantly affected by pore metrics. Introducing methyl groups or using kinked ligands to create smaller pores can enhance the isosteric heat of adsorption and improve H2 adsorption. However, although increasing the overlap of potential energy fields of pore walls increases the heat of H2 adsorption at low pressure, it may be detrimental to the overall adsorption capacity by reducing the pore volume.

Asunto(s)

RESUMEN

Metal-organic frameworks (MOFs)--microporous materials constructed by bridging metal centres with organic ligands--show promise for applications in hydrogen storage, which is a key challenge in the development of the 'hydrogen economy'. Their adsorption capacities, however, have remained insufficient for practical applications, and thus strategies to enhance hydrogen-MOF interactions are required. Here we describe an anionic MOF material built from In(III) centres and tetracarboxylic acid ligands (H(4)L) in which kinetic trapping behaviour--where hydrogen is adsorbed at high pressures but not released immediately on lowering the pressure--is modulated by guest cations. With piperazinium dications in its pores, the framework exhibits hysteretic hydrogen adsorption. On exchange of these dications with lithium cations, no hysteresis is seen, but instead there is an enhanced adsorption capacity coupled to an increase in the isosteric heat of adsorption. This is rationalized by the different locations of the cations within the pores, determined with precision by X-ray crystallography.

Asunto(s)

RESUMEN

H(2) adsorption in (Me(2)NH(2))[In(L)] is enhanced by exchange of Me(2)NH(2)(+) for Li(+) cations; the Li(+)-exchanged material displays a lower isosteric heat for H(2) adsorption than the parent material, indicating that the increase in H(2) capacity is due to an increase in the accessible pore volume on cation exchange, while the lower adsorption enthalpy is consistent with increased pore size.

RESUMEN

Reaction of 4,4'-bipyridine -N, N' -dioxide (L) with a variety of transition-metal salts in MeOH affords a range of coordination polymer products. For the complexes [FeCl 3(mu-L)] infinity, 1, and ([Cu(L) 2(OHMe) 2(mu-L)].2PF 6. n(solv)) infinity, 2, 1D chain structures are observed, whereas ([Mn(mu-L) 3].2ClO 4) infinity, 3, and ([Cu(mu-L) 3].2BF 4) infinity, 4, both show 2D sheet architectures incorporating an unusual 3 (6)- hxl topology. The more common 4 (4)- sql topology is observed in [Cd(ONO 2) 2(mu-L) 2] infinity, 5, ([Cu(OHMe) 2(mu-L) 2].2ZrF 5) infinity, 6, ([Cu(L) 2(mu-L) 2].2EF 6) infinity ( 7 E = P; 8 E = Sb), and ([Et 4N][Cu(OHMe) 0.5(mu-L) 2(mu-FSiF 4F) 0.5].2SbF 6. n(solv)) infinity, 9. In 6, the [ZrF 5] (-) anion, formed in situ from [ZrF 6] (2-), forms 1D anionic chains ([ZrF 5] (-)) infinity of vertex-linked octahedra, and these chains thread through a pair of inclined polycatenated ([Cu(OHMe) 2(mu-L) 2] (2+)) infinity 4 (4)- sql grids to give a rare example of a triply intertwined coordination polymer. 9 also shows a 3D matrix structure with 4 (4)- sql sheets of stoichiometry ([Cu(L) 2] (2+)) infinity coordinatively linked by bridging [SiF 6] (2-) anions to give a structure of 5-c 4 (4).6 (6)- sqp topology. The mononuclear [Cu(L) 6].2BF 4 ( 10) and [Cd(L) 6].2NO 3 ( 11) and binuclear complexes [(Cu(L)(OH 2)) 2(mu-L) 2)].2SiF 6. n(solv), 12, are also reported. The majority of the coordination polymers are free of solvent and are nonporous. Thermal treatment of materials that do contain solvent results in structural disintegration of the complex structures giving no permanent porosity.

RESUMEN

A biporous three dimensional (3,6)-connected coordination framework is reported which exhibits excellent H2 adsorption at low pressures (< or = 1 bar) with high H2 adsorption density.

RESUMEN

The twelve-connected metal-organic frameworks {[Ni(3)(OH)(L)(3)].n(solv)}(infinity) and {[Fe(3)(O)(L)(3)].n(solv)}(infinity) [LH(2) = pyridine-3,5-bis(phenyl-4-carboxylic acid)] have been prepared and characterised: these materials can be desolvated to form porous materials that show adsorption of H(2) up to 4.15 wt% at 77 K.

RESUMEN

A robust 3-D porous structure of formula [Ln2(PDC)3(DMF)2](infinity) has been constructed from lanthanide cations (Ln = Er3+ or Y3+) and the non-linear anionic bridging ligand, pyridine-3,5-dicarboxylate (PDC2-) in dimethylformamide (DMF). The solvated framework polymers {[M2(PDC)3(DMF)2].n(solv)}(infinity) (M = Er, Y) undergo a solid-state, crystal-to-crystal reaction upon heating and are converted via loss of both sorbed and coordinated solvent and rearrangement of the framework core to give a desolvated and porous form with retention of structural integrity. This structural transfer is the first crystallographically characterized system with lanthanide metal ions. These porous products are shown to be effective absorbants for H2, N2, and benzene.

RESUMEN

The robust metal-organic framework compound {[Zn(2)(L)] x 4H(2)O}(infinity) I has been synthesized by hydrothermal reaction of ZnCl(2) and 4,4'-bipyridine-2,6,2',6'-tetracarboxylic acid (H(4)L). Compound I crystallizes in a chiral space group, P4(2)2(1)2, with the chirality generated by the helical chains of hydrogen-bonded guest water molecules rather than by the coordination framework. Removal of guest water molecules from the crystal affords the porous material, [Zn(2)(L)](infinity) (II), which has very high thermal stability and is chemically inert. The N(2) isotherm of II at 77 K suggests a uniform porous structure with a BET surface area of 312.7 m(2)/g and a remarkably strong interaction with N(2) molecules (betaE(0) = 29.6 kJ mol(-)(1)). II also exhibits significant gas storage capacities of 1.08 wt % for H(2) at 4 bar and 77 K and 3.14 wt % (44.0 cm(3)/g, 67 v/v) for methane at 9 Bar at 298 K. The adsorption behavior of II toward organic solvent vapors has also been studied, and isotherms reveal that for different solvent vapors adsorption is dominated by two types of processes, absorbate-absorbate or absorbate-absorbent interactions. The adsorption and desorption kinetic processes in II are determined mainly by the molecular size of the guest species and their interaction with the host.

RESUMEN

The structures of four selenium analogues of the antithyroid drug 6-n-propyl-2-thiouracil [systematic name: 2,3-dihydro-6-n-propyl-2-thioxopyrimidin-4(1H)-one], namely 6-methyl-2-selenouracil, C(5)H(6)N(2)OSe (1), 6-ethyl-2-selenouracil, C(6)H(8)N(2)OSe (2), 6-n-propyl-2-selenouracil, C(7)H(10)N(2)OSe (3), and 6-isopropyl-2-selenouracil, C(7)H(10)N(2)OSe (4), are described, along with that of the dichloromethane monosolvate of 6-isopropyl-2-selenouracil, C(7)H(10)N(2)OSe.CH(2)Cl(2) (4.CH(2)Cl(2)). The extended structure of (1) is a two-dimensional sheet of topology 6(3) with a brick-wall architecture. The extended structures of (2) and (4) are analogous, being based on a chain of eight-membered R(8)(6)(32) hydrogen-bonded rings. In (3) and (4.CH(2)Cl(2)), R(2)(2)(8) hydrogen bonding links molecules into chains. 6-n-Propyl-2-selenouracil.I(2), C(7)H(10)N(2)OSe.I(2) (7), is a charge-transfer complex with a ;spoke' structure, the extended structure of which is based on a linear chain formed principally by intermolecular N-H...O hydrogen bonds. Re-crystallization of 6-ethyl-2-selenouracil or (7) from acetone gave crystals of the diselenides [N-(6'-ethyl-4'-pyrimidone)(6-ethyl-2-selenouracil)(2)(Se-Se)].2H(2)O (9.2H(2)O) or [N-(6'-n-propyl-4'-pyrimidone)(6-n-propyl-2-selenouracil)(2)(Se-Se)] (10), respectively: these have similar extended chain structures formed via N-H...O and C-H...O hydrogen bonds, stacked to give two-dimensional sheets. Re-crystallization of (7) from methanol/acetonitrile led via deselenation to the formation of crystals of 6-n-propyl-2-uracil (11), in which six symmetry-related molecules combine to form a six-membered R(6)(6)(24) hydrogen-bonded ring, with each pair of molecules linked by an R(2)(2)(8) motif.

Asunto(s)