A mesoporous metal-organic framework constructed from a nanosized C3-symmetric linker and [Cu24(isophthalate)24] cuboctahedra

The mesoporous framework [Cu(3)(L)(H(2)O)(3)]·(DMF)(35)·(H(2)O)(35) (NOTT-119) shows on desolvation a BET surface area of 4118(200) m(2) g(-1), a pore volume of 2.35 cm(3) g(-1), a total H(2) uptake of 101 mg g(-1) at 60 bar, 77 K and a total CH(4) uptake of 327 mg g(-1) at 80 bar, 298 K.     

High gas sorption and metal-ion exchange of microporous metal-organic frameworks with incorporated imide groups

Metal-organic frameworks (MOFs), {[Cu(2)(bdcppi)(dmf)(2)]·10DMF·2H(2)O}(n) (SNU-50) and {[Zn(2)(bdcppi)(dmf)(3)]·6DMF·4H(2)O}(n) (SNU-51), have been prepared by the solvothermal reactions of N,N'-bis(3,5-dicarboxyphenyl)pyromellitic diimide (H(4)BDCPPI) with Cu(NO(3))(2) and Zn(NO(3))(2), respectively. Framework SNU-50 has an NbO-type net structure, whereas SNU-51 has a PtS-type net structure. Desolvated solid [Cu(2)(bdcppi)](n) (SNU-50'), which was prepared by guest exchange of SNU-50 with acetone followed by evacuation at 170 °C, adsorbs high amounts of N(2), H(2), O(2), CO(2), and CH(4) gases due to the presence of a vacant coordination site at every metal ion, and to the presence of imide groups in the ligand. The Langmuir surface area is 2450 m(2) g(-1). It adsorbs H(2) gas up to 2.10 wt% at 1 atm and 77 K, with zero coverage isosteric heat of 7.1 kJ mol(-1), up to a total of 7.85 wt% at 77 K and 60 bar. Its CO(2) and CH(4) adsorption capacities at 298 K are 77 wt% at 55 bar and 17 wt% at 60 bar, respectively. Of particular note is the O(2) adsorption capacity of SNU-50' (118 wt% at 77 K and 0.2 atm), which is the highest reported so far for any MOF. By metal-ion exchange of SNU-51 with Cu(II), {[Cu(2)(bdcppi)(dmf)(3)]·7DMF·5H(2)O}(n) (SNU-51-Cu(DMF)) with a PtS-type net was prepared, which could not be synthesized by a direct solvothermal reaction.     

Structure, adsorption and magnetic properties of chiral metal-organic frameworks bearing linear trinuclear secondary building blocks

The reactions of new chiral organic ligands trimesoyltri(L-alanine) (L-TMTAH(3)) or trimesoyltri(D-alanine) (D-TMTAH(3)) with transition metal salts in the presence of an ancillary ligand of 4,4'-bipyridine gave two pairs of three dimensional frameworks [Co(3)(L-TMTA)(2)(4,4'-bpy)(4)]·28H(2)O (1), [Co(3)(D-TMTA)(2)(4,4'-bpy)(4)]·28H(2)O (2) [Ni(3)(L-TMTA)(2)(4,4'-bpy)(4)]·2C(2)H(5)OH·14H(2)O (3) and [Ni(3)(D-TMTA)(2)(4,4'-bpy)(4)]·2C(2)H(5)OH·14H(2)O (4). These compounds were characterized by elemental analysis, IR, and X-ray powder diffraction analysis and the structures of 1-3 were determined from X-ray single crystal diffraction analysis. Complexes 1-4 feature linear trinuclear secondary building blocks [M(3)(COO)(4)](2+) formed via the connection of three metal ions by four carboxylato groups from four TMTA(3-) ligands. Every adjacent two linear trinuclear secondary building blocks are linked by one and three 4,4'-bipyridine molecules along the a and c axis, respectively, to form two-dimensional sheets, which are further connected by TMTA(3-) ligands to construct a porous three dimensional framework with one-dimensional channels. Compound 3 was taken as an example to investigate the adsorption properties of compounds 1-4. It revealed a saturated hydrogen uptake of 216.6 cm(3) g(-1) (2.0 wt%) at 11.1 atm measured at 77 K, a maximum CO(2) uptake of 119.4 cm(3) g(-1) (23.5 wt%) at 19.5 atm measured at 298 K and a saturated CH(4) uptake of 77.8 cm(3) g(-1) (5.6 wt%) at 27.1 atm measured at 298 K. The magnetic studies of complexes 1 and 3 indicate the presence of antiferromagnetic interactions between the metal ions in the two compounds.     

Further investigation of the effect of framework catenation on hydrogen uptake in metal-organic frameworks

Hydrogen-sorption studies have been carried out for the catenation isomer pairs of PCN-6 and PCN-6' (both have the formula of Cu(3)(TATB)(2), where TATB represents 4,4',4'-s-triazine-2,4,6-triyl-tribenzoate with a formula of C(24)H(12)N(3)O(6)). Inelastic neutron scattering (INS) studies reveal that the initial sites occupied by adsorbed H(2) are the open Cu centers of the paddlewheel units with comparable interaction energies in the two isomers. At high H(2) loadings, where the H(2) molecules adsorb mainly on or around the organic linkers, the interaction is found to be substantially stronger in catenated PCN-6 than in noncatenated PCN-6', leading to much higher H(2) uptake in the isomer with catenation. Hydrogen sorption measurements at pressures up to 50 bar demonstrate that framework catenation can be favorable for the enhancement of hydrogen adsorption. For example, the excess hydrogen uptake of PCN-6 is 72 mg/g (6.7 wt %) at 77 K/50 bar or 9.3 mg/g (0.92 wt %) at 298 K/50 bar, respectively, and that for PCN-6' is 42 mg/g (4.0 wt %) at 77 K/50 bar or 4.0 mg/g (0.40 wt %) at 298 K/50 bar. Importantly, PCN-6 exhibits a total hydrogen uptake of 95 mg/g (8.7 wt %) (corresponding to a total volumetric value of 53.0 g/L, estimated based on crystallographic density) at 77 K/50 bar and 15 mg/g (1.5 wt %) at 298 K/50 bar. Significantly, the expected usable capacity of PCN-6 is as high as 75 mg/g (or 41.9 g/L) at 77 K, if a recharging pressure of 1.5 bar is assumed.     

Increasing nuclearity of secondary building units in porous cobalt(II) metal-organic frameworks: variation in structure and H2 adsorption

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.     

Reduction of carbon monoxide by [(TMTAA)Rh]2 to form a dimetal ketone complex

Benzene solutions of [(TMTAA)Rh](2) (1) react with CO (P(CO) = 0.8-20 atm; T = 298 K) by cleaving the Rh(II)-Rh(II) bond to form dirhodium(III) ketone (TMTAA)Rh-C(O)-Rh(TMTAA) [2; ν(CO) = 1726 cm(-1); (1)J(103)Rh(13)C(O)(103)Rh = 45 Hz]. Thermodynamic values for the reaction of 1 with CO to form 2 were evaluated from equilibrium constant measurements [K(1)(298 K) = 5.0(0.6) × 10(3), ΔG(1)°(298 K) = -5.0(0.1) kcal mol(-1), ΔH(1)° = -14(1) kcal mol(-1), and ΔS(1)° = -30(3) cal K(-1) mol(-1)].     

An interpenetrated metal-organic framework and its gas storage behavior: simulation and experiment

A new metal-organic framework, called UHM-6 (UHM: University of Hamburg Materials), based on the copper paddle wheel motif and a novel organosilicon linker, 4',4″-(dimethylsilanediyl)bis(biphenyl-3,5-dicarboxylic acid) (sbbip), has been synthesized and characterized with regard to its gas storage behavior up to 1 bar for hydrogen, methane, and carbon dioxide. The 2-fold interpenetrated microporous framework of UHM-6 is isoreticular to PMOF-3 (Inorg. Chem.2009, 48, 11507) and is composed of cuboctahedral cages of Cu(2) paddle wheels connected via nonlinear organosilicon units. The structure (SG I422, No. 97) is characterized by straight channels running along the [001] and [110] direction. UHM-6 reveals a specific surface area of S(BET) ~ 1200 m(2) g(-1) and a specific micropore volume of V(micropore) ~ 0.48 cm(3) g(-1). At 1 bar the activated form of UHM-6 shows a hydrogen uptake of 1.8 wt % (77 K), a methane uptake of 0.8 mmol g(-1) (293 K), and a carbon dioxide uptake of 3.3 mmol g(-1) (273 K). Accompanying theoretical grand-canonical Monte Carlo (GCMC) simulations show an overall good agreement with the experimental results. Furthermore, GCMC adsorption simulations for three binary equimolar mixtures (CH(4)/H(2), CO(2)/H(2), and CO(2)/CH(4)) were carried out (T = 298 K) to assess the potential for gas separation/purification applications.     

Structural chemistry, monoclinic-to-orthorhombic phase transition, and CO2 adsorption behavior of the small pore scandium terephthalate, Sc2(O2CC6H4)CO2)3, and its nitro- and amino-functionalized derivatives

The crystal structure of the small pore scandium terephthalate Sc(2)(O(2)CC(6)H(4)CO(2))(3) (hereafter Sc(2)BDC(3), BDC = 1,4-benzenedicarboxylate) has been investigated as a function of temperature and of functionalization, and its performance as an adsorbent for CO(2) has been examined. The structure of Sc(2)BDC(3) has been followed in vacuo over the temperature range 140 to 523 K by high resolution synchrotron X-ray powder diffraction, revealing a phase change at 225 K from monoclinic C2/c (low temperature) to Fddd (high temperature). The orthorhombic form shows negative thermal expansivity of 2.4 × 10(-5) K(-1): Rietveld analysis shows that this results largely from a decrease in the c axis, which is caused by carboxylate group rotation. (2)H wide-line and MAS NMR of deuterated Sc(2)BDC(3) indicates reorientation of phenyl groups via π flips at temperatures above 298 K. The same framework solid has also been prepared using monofunctionalized terephthalate linkers containing -NH(2) and -NO(2) groups. The structure of Sc(2)(NH(2)-BDC)(3) has been determined by Rietveld analysis of synchrotron powder diffraction at 100 and 298 K and found to be orthorhombic at both temperatures, whereas the structure of Sc(2)(NO(2)-BDC)(3) has been determined by single crystal diffraction at 298 K and Rietveld analysis of synchrotron powder diffraction at 100, 298, 373, and 473 K and is found to be monoclinic at all temperatures. Partial ordering of functional groups is observed in each structure. CO(2) adsorption at 196 and 273 K indicates that whereas Sc(2)BDC(3) has the largest capacity, Sc(2)(NH(2)-BDC)(3) shows the highest uptake at low partial pressure because of strong -NH(2)···CO(2) interactions. Remarkably, Sc(2)(NO(2)-BDC)(3) adsorbs 2.6 mmol CO(2) g(-1) at 196 K (P/P(0) = 0.5), suggesting that the -NO(2) groups are able to rotate to allow CO(2) molecules to diffuse along the narrow channels.     

New three-dimensional porous metal organic framework with tetrazole functionalized aromatic carboxylic Acid: synthesis, structure, and gas adsorption properties

5-(1H-Tetrazol-1-yl)isophthalic acid (H(2)L) reacts with Cu(II) ion forming a new metal-organic framework {[CuL]·DMF·H(2)O}(∞) (1) (DMF = N,N-dimethylformamide), with a rutile-related type net topology. Compound 1 possesses a 3D structure with 1D channels that can be desolvated to yield a microporous material. Adsorption properties (N(2), H(2), O(2), CO(2), and CH(4)) of the desolvated solid [CuL] (1a) have been studied, and the results exhibit that 1a possesses fairly good capability of gas sorption for N(2), H(2), O(2), and CO(2) gases, with high selectivity ratios for O(2) over H(2) at 77 K and CO(2) over CH(4) at 195, 273, and 298 K. Furthermore, 1a has excellent O(2) uptake at 77 K and a remarkably high quantity of adsorption for CO(2) at room temperature (298 K) and atmospheric pressure, suggesting its potential applications in gas separation or purification.     

Investigation of porous Ni-based metal-organic frameworks containing paddle-wheel type inorganic building units via high-throughput methods

In the search of Ni based metal-organic frameworks (MOFs) containing paddle-wheel type building units, three chemical systems Ni(2+)/H(n)L/base/solvent with H(n)L = H(3)BTC (1,3,5-benzenetricarboxylic acid), H(3)BTB (4,4',4',-benzene-1,3,5-triyl-tris(benzoic acid)), and H(2)BDC (terephthalic acid) were investigated using high-throughput (HT) methods. In addition to the conventional heating, for the first time HT microwave assisted synthesis of MOFs was carried out. Six new compounds were discovered, and their fields of formation were established. In the first system, H(3)BTC was employed and a comprehensive HT-screening of compositional and process parameters was conducted. The synthesis condition for the Ni paddle-wheel unit was determined and two compounds [Ni(3)(BTC)(2)(Me(2)NH)(3)]·(DMF)(4)(H(2)O)(4) (1a) and [Ni(6)(BTC)(2)(DMF)(6)(HCOO)(6)] (1b) were discovered (Me(2)NH = dimethylamine, DMF = dimethylformamide). In the second system, the use of the extended tritopic linker H(3)BTB and the synthesis conditions for the paddle-wheel units led to the porous MOF, [Ni(3)(BTB)(2)(2-MeIm)(1.5)(H(2)O)(1.5)]·(DMF)(9)(H(2)O)(6.5) (2), (2-MeIm = 2-methylimidazole). This compound shows a selective adsorption of H(2)O and H(2) with a strong hysteresis. In the third system, H(2)BDC was used, and the base (DABCO) was incorporated as a bridging ligand into all structures. Thus, two pillared layered porous MOFs [Ni(2)(BDC)(2)(DABCO)]·(DMF)(4)(H(2)O)(1.5) (3a) and [Ni(2)(BDC)(2)(DABCO)]·(DMF)(4)(H(2)O)(4) (3b) as well as a layered compound [Ni(BDC)(DABCO)]·(DMF)(1.5)(H(2)O)(2) (3c) were isolated. The 3a and 3b polymorphs of the [Ni(2)(BDC)(2)(DABCO)] framework can be selectively synthesized. The combination of microwave assisted heating, low overall concentration, stirring of the reaction mixtures, and an excess of DABCO yields a highly crystalline pure phase of 3b. The fields of formation of all compounds were established, and scale-up was successfully performed for 1b, 2, 3a, 3b, and 3c. All compounds were structurally characterized. In addition to IR, elemental and TG analyses, gas and vapor sorption experiments were carried out.     

Flexible and hydrophobic Zn-based metal-organic framework

A zinc-based metal-organic framework Zn(2)(adb)(2)(dabco)·4.5 DMF (K) (DUT-30(Zn), DUT = Dresden University of Technology, adb = 9,10-anthracene dibenzoate, dabco =1,4-diazabicyclo[2.2.2]octane, DMF = N,N-dimethylformamide) was synthesized using a solvothermal route. This MOF exhibits six crystallographic guest dependent phases. Two of them were characterized via single crystal X-ray analysis. The as-synthesized phase K crystallizes in the orthorhombic space group Fmmm, with a = 9.6349(9), b = 26.235(3), and c = 28.821(4) ? and consists of two interpenetrated pillar-layer networks with pcu topology. When the substance loses 0.5 DMF molecules per formula unit, a phase transition from the kinetic phase K to a thermodynamic phase T occurs. Zn(2)(adb)(2)(dabco)·4 DMF (T) crystallizes in the tetragonal space group I4/mmm, with a = 19.5316(8) and c = 9.6779(3) ?. During the evacuation the DUT-30(Zn) undergoes again the structural transformation to A. The activated compound A shows the gate pressure effect in the low pressure region of nitrogen physisorption isotherm and has a BET surface area of 960 m(2 )g(-1) and a specific pore volume of 0.43 cm(3) g(-1). Furthermore, DUT-30(Zn) exhibits a hydrogen storage capacity of 1.12 wt % at 1 bar, a CO(2) uptake of 200 cm(3) g(-1) at -78 °C and 0.9 bar, and a n-butane uptake of 3.0 mmol·g(-1) at 20 °C. The N(2) adsorption process was monitored in situ via X-ray powder diffraction using synchrotron radiation. A low temperature induced transformation of phase A to phase V could be observed if the compound was cooled under vacuum to -196 °C. A further crystalline phase N could be identified if the framework was filled with nitrogen at -196 °C. Additionally, the treatment of activated phase A with water leads to the new phase W.     

A metal-organic framework with highly polar pore surfaces: selective CO2 adsorption and guest-dependent on/off emission properties

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.     

Flexible porous coordination polymers constructed from 1,2-bis(4-pyridyl)hydrazine via solvothermal in situ reduction of 4,4'-azopyridine

Solvothermal reactions of Zn(NO(3))(2), 1,4-benzenedicarboxylic acid (H(2)bdc), and 4,4'-azopyridine (azpy) in different conditions yielded [Zn(bdc)(bphy)]·DMF·H(2)O (1a, bphy = 1,2-bis(4-pyridyl)hydrazine, DMF = N,N-dimethylformamide) and [Zn(bdc)(bphy)]·EtOH·H(2)O (1b) with two-fold interpenetrated dmp topology and [Zn(2)(bdc)(2)(bphy)]·1.5EtOH·H(2)O (2a) and [Zn(2)(bdc)(2)(bphy)]·DMA·1.5H(2)O (2b, DMA = N,N-dimethylacetamide) with two-fold interpenetrated pcu topology. The in situ reduction of azpy to bphy was confirmed by single-crystal structures and LC-MS analyses of the acid-digested crystalline samples, as well as controlled solvothermal experiments. Removal of the guest molecules in 1a/1b and 2a/2b converts the materials to guest-free phases [Zn(bdc)(bphy)] (1) and [Zn(2)(bdc)(2)(bphy)] (2), respectively, which were identified by PXRD. CO(2) sorption experiments performed at 195 and 298 K showed low porosity for 1 and gated sorption behavior for 2. At 298 K, 2 exhibits high selectivity for adsorbing CO(2) over CH(4).     

Three-dimensional metal-organic framework with highly polar pore surface: H2 and CO2 storage characteristics

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.     

Magnesium aminoethyl phosphonate (Mg(AEP)(H2O)): an inorganic-organic hybrid nanomaterial with high CO2:N2 sorption selectivity

The inorganic-organic hybrid magnesium aminoethyl phosphonate (Mg(AEP)(H(2)O), particle diameter: 20 nm; specific surface area: 322(10) m(2) g(-1); pore volume: 0.9(1) cm(3) g(-1)) shows reversible CO(2) sorption (152(5) mg g(-1)) at high pressure (≤110 bar). In contrast, N(2) uptake remains below 1.0(1) mg g(-1). Based on this selectivity (～100%) Mg(AEP)(H(2)O) expands the range of materials available for CO(2) capture.     

Two mixed-valence vanadium(III,IV) phosphonoacetates with 16-ring channels: H2(DABCO)[V(IV)O(H2O)V(III)(OH)(O3PCH2CO2)2].2.5H2O and H2(PIP)[V(IVO)(H2O)V(III)(OH)(O3PCH2CO2)2].2.5H2O

Two isostructural mixed-valence vanadium phosphonoacetates H2(DABCO)[V(IV)O(H2O)V(III)(OH)(O3PCH2CO2)2].2.5H2O (1) and H2(PIP)[V(IV)O(H2O)V(III)(OH)(O3PCH2CO2)2].2.5H2O (2) have been synthesized. They crystallize in the orthorhombic space group Pnna with a = 7.0479(10) A, b = 15.307(2) A, and c = 17.537(3) A for 1 and a = 7.0465(9) A, b = 15.646(2) A, and c = 17.396(2) A for 2. X-ray single-crystal diffraction reveals that 1 and 2 have a three-dimensional open framework featuring 16-ring ellipsoid channels that are filled with doubly protonated 1,4-diazabicyclo[2,2,2]octanium/piperazinium cations and water molecules. According to the classification in metal-organic frameworks, 1 and 2 contain infinite (-O-V-)(infinity) chains that are cross-linked by "metalloligand" [VO(H2O)(O3PCH2CO2)2](4-) into a 3-D net of the sra topology. The temperature dependence of the magnetic susceptibility of 1 shows that the chi(m)T value in the range of 60-320 K is constant of 1.105 cm3 K mol(-1)/V2 unit, and upon further cooling, the chi(m)T value rapidly increases to 1.81 cm3 K mol(-1) at 2 K. The corresponding effective magnetic moment (mu(eff))/V2 unit varies from 2.97 mu(B) at 320 K to 3.80 mu(B) at 2 K. The magnetic data in the range of 2-320 K follow the Curie-Weiss law with C = 1.074 cm3 K mol(-1) and Theta= -1.34 K.     

High capacity gas storage by a 4,8-connected metal-organic polyhedral framework

The polyhedral complex [Cu(4)L(H(2)O)(4)]solv (NOTT-140) shows a 4,8-connected structure of rare scu topology comprising octahedral and cuboctahedral cages; desolvated NOTT-140a shows a total CO(2) uptake of 314.6 cm(3) (STP) cm(-3) at 20 bar, 293 K, and a total H(2) uptake of 6.0 wt% at 20 bar, 77 K.     

A porous framework polymer based on a zinc(II) 4,4'-bipyridine-2,6,2',6'-tetracarboxylate: synthesis, structure, and "zeolite-like" behaviors

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.     

A robust porous metal-organic framework with a new topology that demonstrates pronounced porosity and high-efficiency sorption/selectivity properties of small molecules

A robust porous metal-organic framework (MOF), [Co(3)(ndc)(HCOO)(3)(μ(3)-OH)(H(2)O)](n) (1) (H(2)ndc=5-(4-pyridyl)-isophthalic acid), was synthesized with pronounced porosity. MOF 1 contained two different types of nanotubular channels, which exhibited a new topology with the Schlafli symbol of {4(2).6(5).8(3)}{4(2).6}. MOF 1 showed high-efficiency for the selective sorption of small molecules, including the energy-correlated gases of H(2), CH(4), and CO(2), and environment-correlated steams of alcohols, acetone, and pyridine. Gas-sorption experiments indicated that MOF 1 exhibited not only a high CO(2)-uptake (25.1 wt % at 273 K/1 bar) but also the impressive selective sorption of CO(2) over N(2) and CH(4). High H(2)-uptake (2.04 wt % at 77 K/1 bar) was also observed. Moreover, systematic studies on the sorption of steams of organic molecules displayed excellent capacity for the sorption of the homologous series of alcohols (C(1)-C(5)), acetone, pyridine, as well as water.     

Structures and H2 adsorption properties of porous scandium metal-organic frameworks

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).