Heat Of H2 Adsorption Research Articles

Computational fluid dynamics simulation of Fischer-Tropsch synthesis coupled with a novel reaction kinetics using trimetallic catalyst over a biomass-based support

A mathematical modeling based on the computational fluid dynamics (CFD) was performed in this work. The reactive flow behavior in a tubular reactor was modeled for Fischer-Tropsch synthesis (FTS) using a novel trimetallic catalyst supported on a low-cost and renewable carbonaceous material. The fixed bed reactor was simulated as a porous media using a commercial software package (COMSOL Multiphysics). In this study, major attention has been paid to the species transport and reaction kinetics, as a fundamental stage in CFD simulation of FTS. The reaction kinetics was evaluated using Eley-Rideal theory assuming the molecular adsorption of CO based on the enol mechanism. Furthermore, the products distribution was accounted in the kinetics study by defining a mathematical expression and the kinetics parameters were optimized using genetic algorithm (GA). The activation energy and heat of H2 adsorption were estimated as 62.63 and −29.52 kJ/mol, respectively. The role of operational conditions was critically evaluated on the partial pressure profiles of the species, and the CFD results were validated with the experimental data. While increasing total pressure improved the partial pressure of C5+ hydrocarbons to 1.2 bar, increasing temperature to 310 °C limited the chain growth. The employed modeling and novel catalyst design can provide promising overview of the FTS reaction mechanism and products selectivity in fixed bed reactors.

Adsorption of hydrogen and carbon dioxide in zeolitic imidazolate framework structure with SOD topology: experimental and modelling studies

The aim of this work is to develop insights into adsorption of hydrogen and carbon dioxide in a zeolitic imidazolate framework, ZIF-8, using high-pressure adsorption studies, adsorption isotherm model fitting, and DFT investigation of preferential adsorption sites and binding energies. The robustness of ZIF series metal–organic frameworks has drawn interest towards its utility in large scale applications in gas storage and separation. We use room temperature synthesis of ZIF-8 using DMF as a solvent, and benchmarked it against typical solvothermal synthesis. The resulting material is characterized using XRD, SEM, TG–DSC and N2 adsorption isotherm. High-pressure volumetric adsorption of the activated materials is conducted to analyze the hydrogen and carbon dioxide storage capacities up to 50 and 40 bar, respectively. ZIF-8 shows maximum H2 storage capacity of 3.13 wt% at 50 bar and 77 K, and CO2 storage capacity of 46 wt% at 40 bar and 300 K. The parameters of Unilan adsorption isotherm are estimated from the equilibrium adsorption data and isosteric heats of adsorption for H2 and CO2 on ZIF-8 are computed. DFT calculations are used to obtain preferential adsorption sites of H2 and CO2. Adsorption enthalpy values were calculated from DFT as − 7.08 and − 25.98 kJ/mol, respectively for H2 and CO2 at the most preferred sites. We found a close agreement between isosteric heat of adsorption of hydrogen (− 4.68 kJ/mol) and the enthalpy of hydrogen adsorption from DFT (− 6.04 kJ/mol) at 77 K.

Fundamentals of hydrogen storage processes over Ru/SiO2 and Ru/Vulcan

Hydrogen adsorption and desorption over Ru/SiO2 and Ru/Vulcan are investigated in terms of hydrogen storage and release characteristics by both dynamic and static experiments. Ru particle dispersions as a function of metal loading were determined by HR-TEM and volumetric chemisorption experiments. Vulcan was more accommodating for spillover hydrogen than SiO2. High Ru dispersions, i.e., small particle sizes, favored the amount of hydrogen spillover to Vulcan, as revealed by temperature programmed desorption (TPD) of hydrogen. TPD of hydrogen under He flow experiments over Ru/SiO2 and Ru/Vulcan materials revealed a low temperature process (up to 200 °C) attributed to desorption of weakly bound hydrogen from Ru metal surface. A high temperature process (above 450 °C) was attributed to diffusion of hydrogen from the support to the Ru particle and desorption at the Ru sites. Hydrogen adsorbs strongly on Ru metal, as indicated by the initial heats of H2 adsorption measured as 100 kJ/mol over 1 wt% Ru/Vulcan by adsorption calorimetry. At higher coverages, heat of adsorption of hydrogen was measured as 10 kJ/mol. Low heat of adsorption of hydrogen at high coverages indicate multilayer weak adsorption of hydrogen over the storage material, which can desorb at lower temperatures.

H2 adsorption on Cu(I)-ZSM-5: Exploration of Cu(I)-exchange in solution

A new Cu(I)-exchange method for zeolites in liquid media (acetonitrile) was developed with Cu/Al ratios surpassing 0.5 with ZSM-5 crystals containing pure Cu(I) cations without impurities such as Cl ions. The method resulted in a higher Cu/Al ratio (0.78) for mesoporous [B]-ZSM-5 when compared to microporous [Al]-ZSM-5 and [B]-ZSM-5 (0.55 and 0.66 respectively). H2 storage capacities of these Cu(I)-exchanged zeolites were investigated at 323 K along with their differential heat of H2 adsorption using adsorption calorimetry. H2 storage capacities as high as 0.03 wt. % at 323 K and 40 kPa were achieved on [Al] and [B]-ZSM-5 and mesoporous [B]-ZSM-5 showed an outstanding H2/Cu ratio of 1.03 at 323 K and below 100 kPa. Coverage-dependent differential adsorption heats were found to be ranging from 95 kJ/mol to 5 kJ/mol with observed values of 30–10 kJ/mol for H2/Cu ratios between 0.05 and 0.15.

H2 Adsorption on Cu(I)–SSZ-13

We report H2 adsorption capacities reaching 0.05 wt % at 303 K and at 1 atm H2 pressure on solid-state CuCl-exchanged [Al]-SSZ-13 and [B]-SSZ-13 zeolites. Differential heat of H2 adsorption is found in the range between 16 and 48 kJ mol H2–1 on Cu(I)-SSZ-13 at 323 K and isosteric heat of adsorption is found between 20 and 55 kJ mol H2–1 on Cu(I)-[B]-SSZ-13 at temperatures between 293 and 323 K. Strong interactions between H2 and the copper cations in Cu(I)-SSZ-13 are evidenced using Rietveld refinements of neutron powder diffraction patterns revealing Cu–deuterium (D2) distances of 2.3(2) and 2.41(1) A. A temperature-dependent Cu(I) migration—away from the six-membered ring (6MR) and eight-membered ring (8MR)—is related to the high adsorption capacities of the samples at 303 K. At 10 K, access to Cu(I) at 6MR is sterically hindered by framework oxygen atoms (Cu–Oframework distance of 2.196(5) A), rationalizing the low H2 adsorption capacities of Cu(I)-SSZ-13 samples as compared to Na-SSZ-13 at 77 K.

Hydrogen storage in a potassium-ion-bound metal-organic framework incorporating crown ether struts as specific cation binding sites.

To develop a metal-organic framework (MOF) for hydrogen storage, SNU-200 incorporating a 18-crown-6 ether moiety as a specific binding site for selected cations has been synthesized. SNU-200 binds K(+), NH4(+), and methyl viologen (MV(2+)) through single-crystal to single-crystal transformations. It exhibits characteristic gas-sorption properties depending on the bound cation. SNU-200 activated with supercritical CO2 shows a higher isosteric heat (Qst) of H2 adsorption (7.70 kJ mol(-1)) than other zinc-based MOFs. Among the cation inclusions, K(+) is the best for enhancing the isosteric heat of the H2 adsorption (9.92 kJ mol(-1)) as a result of the accessible open metal sites on the K(+) ion.

Hydrogen Storage in a Potassium‐Ion‐Bound Metal–Organic Framework Incorporating Crown Ether Struts as Specific Cation Binding Sites

AbstractTo develop a metal–organic framework (MOF) for hydrogen storage, SNU‐200 incorporating a 18‐crown‐6 ether moiety as a specific binding site for selected cations has been synthesized. SNU‐200 binds K+, NH4+, and methyl viologen(MV2+) through single‐crystal to single‐crystal transformations. It exhibits characteristic gas‐sorption properties depending on the bound cation. SNU‐200 activated with supercritical CO2 shows a higher isosteric heat (Qst) of H2 adsorption (7.70 kJ mol−1) than other zinc‐based MOFs. Among the cation inclusions, K+ is the best for enhancing the isosteric heat of the H2 adsorption (9.92 kJ mol−1) as a result of the accessible open metal sites on the K+ ion.

Microcalorimetric Studies on Co–Re/γ-Al2O3 Catalysts with Na Impurities for Fischer–Tropsch Synthesis

In Fischer–Tropsch synthesis (FTS), sodium impurities originating from biomass feedstock can be introduced into the catalyst as traces via the synthesis gas. The addition of small amounts of Na to a Co-based Fischer–Tropsch catalyst has been studied in terms of catalytic performance and key characteristics. The Na addition had a severe effect on the catalytic performance, causing significant suppression of the catalytic activity. Small amounts of Na (up to 1000 ppm) had no effect on chemisorption amounts or heats of adsorption for H2 or CO. Higher amounts of Na added (10 000 or 20 000 ppm) had a dramatic effect on the activity and selectivity in CO hydrogenation. Minor changes in heats of adsorption and chemisorption uptake suggest that the effect of large amounts of Na can be assigned both to geometric and electronic effects. Stronger adsorption of the reactants in parallel to the diffusion barrier caused by the site blocking from Na atoms could explain the dramatic drop in the catalytic activity. For th...

Effect of Pillar Modules and Their Stoichiometry in 3D Porous Frameworks of Zn(II) with [Fe(CN)6]3–: High CO2/N2 and CO2/CH4 Selectivity

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.

Facile Synthesis of Hydroxy‐Modified MOF‐5 for Improving the Adsorption Capacity of Hydrogen by Lithium Doping

A facile synthesis of partially hydroxy-modified MOF-5 and its improved H2-adsorption capacity by lithium doping are reported. The reaction of Zn(NO3)2·6H2O with a mixture of terephthalic acid (H2BDC) and 2-hydroxyterephthalic acid (H2BDC-OH) in DMF gave hydroxy-modified MOF-5 (MOF-5-OH-x), in which the molar fraction (x) of BDC-OH(2-) was up to 0.54 of the whole ligand. The MOF-5-OH-x frameworks had high BET surface areas (about 3300 m(2) g(-1)), which were comparable to that of MOF-5. We suggest that the MOF-5-OH-x frameworks are formed by the secondary growth of BDC(2-)-rich MOF-5 seed crystals, which are nucleated during the early stage of the reaction. Subsequent Li doping into MOF-5-OH-x results in increased H2 uptake at 77 K and 0.1 MPa from 1.23 to 1.39 wt.% and an increased isosteric heat of H2 adsorption from 5.1-4.2 kJ mol(-1) to 5.5-4.4 kJ mol(-1).

Methoxy‐Modified MOF‐5: A MOF‐5 Framework Prepared by a Mixed Ligand Approach

AbstractIn this paper, a series of MOF‐5 frameworks based on a mixed diacid composition, i.e. 2‐methoxyterephthalic acid and terephthalic acid, was synthesized by using a mixed‐ligand approach. The MOF‐5 structure remains intact when the 2‐methoxyterephthalate concentration is in the range of 0–75 mol‐%. By using this approach, the H2 uptake capacity of MOF‐5, at 77 K and 1 bar, can be improved by 10 % at a 2‐methoxyterephthalate concentration of 75 mol‐% (1.45 wt.‐% vs. 1.32 wt.‐% for MOF‐5). This improvement is due to an enhanced isosteric heat of H2 adsorption on a statistically determined number of sites.

Design of Flexible Lewis Acidic Sites in Porous Coordination Polymers by using the Viologen Moiety

Charged up: A novel porous coordination polymer with a charged organic surface (COS) comprising a zwitterionic organic linker, viologen, has been synthesized. The COS shows strong Lewis acidity accompanied with flexibility, and the isosteric heat of H2 adsorption is 9.5 kJ mol−1, which is comparable to that of open metal sites (OMSs).

Phthalimide based polymers of intrinsic microporosity

A series of phthalimide based microporous polymers were successfully prepared by conventional nucleophilic substitution reaction of several newly synthesized fluoro-monomers with commercially available 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethylspirobisindane. FTIR, 1H NMR, and elemental analyses were used to identify the proposed structures of the polymers. The synthesized polymers are of high molecular weight as demonstrated by Gel Permeation Chromatography (GPC). Thermogravimetric analysis shows that the prepared polymers were stable up to 300 °C. From the porosity analysis it is clear that the prepared polymers are analogous to polymers of intrinsic microporosity (PIMs) with high surface area (500–900 m2/g). The t-plot analysis shown that the major contribution to the specific surface area is arising from the micropore surface area with narrow size distribution of ultramicropores as confirmed by the Horvath-Kawazoe (H-K) analysis. The hydrogen storage capacity of the prepared PIM-R(1–7) and CO-PIM(3,4,6,7) were promising (up to 1.26 wt%, 77 K, at 1.13 bar) with high isoteric heats of H2 adsorption (8.5 kJ/mol).The results of this study demonstrate that controlling the appropriate monomer content via the three-dimensional structure can provide a uniform microporous morphology in the target polymers.

Nanosize Zr-metal organic framework (UiO-66) for hydrogen and carbon dioxide storage

A nanosize Zr-metal organic framework (Zr-MOF, UiO-66) with a uniformed particle size around 100nm was solvothermally synthesized and activated by solvent exchange method, vacuum drying and heating. The activation process with an exchangeable guest solvent produced the Zr-MOF with a high surface area by removal almost all guest and free terephthalic acid molecules from the pores enhancing its capacity for adsorption. The nanosize Zr-MOF also showed strong thermal stability up to 753K. The Zr-MOF was tested for hydrogen and carbon dioxide adsorption at varying pressures and temperatures and it exhibited adsorption capacity of 1.6wt% (H2) at 1atm, 77K and 79cc (CO2)g−1 at 1atm, 273K, respectively. The heat of H2 adsorption was estimated to be 6–12kJmol−1 while the heat of CO2 adsorption was determined to be around 28kJmol−1.

Enhanced isosteric heat of H2 adsorption by inclusion of crown ethers in a porous metal–organic framework

Inclusion of 18-crown-6 or 15-crown-5 in a porous MOF increased the isosteric heats of H(2) adsorption significantly, which are comparable to MOFs containing open metal sites.

Imine-Linked Microporous Polymer Organic Frameworks

Imine-linked microporous polymer organic frameworks (POFs) were synthesized via Schiff base condensation between 1,3,5-triformylbenzene and several readily available diamine monomers. Our facile, one-pot approach results in quantitative yields of POFs with the flexibility to incorporate several functional groups in their pores for tuning the interaction of their surface with different guest molecules. Synthesized POFs exhibit high specific surface areas (up to 1500 m2 g−1) as well as high isosteric heats of H2 adsorption (up to 8.2 kJ mol−1).

Charged soc metal‐organic framework for high‐efficacy H2 adsorption and syngas purification: Atomistic simulation study

AbstractH2 adsorption and syngas purification in charged soc metal‐organic framework are investigated using atomistic simulations. As experimentally observed, the extraframework NO3− ions are entrapped in carcerand‐like capsule with negligible mobility. At low pressure, H2 adsorption occurs concurrently at multiple sites near the exposed indium atoms and organic components. The capsule is accessible at high pressure through the surrounding channels by restricted windows. Adsorption sites identified are remarkably consistent with inelastic neutron scattering measurements. The isotherm and isosteric heat of H2 adsorption predicted match well with experimental data. As loading rises, the isosteric heat remains nearly constant, revealing the homogeneity of adsorption sites. CO2/H2 selectivity in syngas adsorption is up to 600 and substantially higher than other nanoporous materials. With a trace of H2O, the selectivity increases slightly at low pressure due to promoted adsorption of CO2 by H2O bound proximally to the exposed indium atoms, but decreases at high pressure as a consequence of competitive adsorption of H2O over CO2. © 2009 American Institute of Chemical Engineers AIChE J, 2009

High Capacity Hydrogen Adsorption in Cu(II) Tetracarboxylate Framework Materials: The Role of Pore Size, Ligand Functionalization, and Exposed Metal Sites

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.

Enhanced H2 Adsorption in Isostructural Metal−Organic Frameworks with Open Metal Sites: Strong Dependence of the Binding Strength on Metal Ions

Metal-organic frameworks (MOFs) with open metal sites exhibit a much stronger H2 binding strength than classical MOFs, due to the direct interaction between H2 and the coordinately unsaturated metal ions. Here we report a systematic study of the H2 adsorption on a series of isostructural MOFs, M2(dhtp) (M = Mg, Mn, Co, Ni, Zn). The experimental, initial isosteric heats of adsorption for H2 (Qst) of these MOFs range from 8.5 to 12.9 kJ/mol, with increasing Qst in the following order: Zn, Mn, Mg, Co, and Ni. The H2 binding energies derived from first-principles calculation follow the same trend as the experimental observation on Qst, confirming the electrostatic Coulomb attraction between the H2 and the open metals being the major interaction. We also found a strong correlation between the metal ion radius, the M-H2 distance, and the H2 binding strength, which provides a viable, empirical method to predict the relative H2 binding strength of different open metals.

A Comparison of the H2 Sorption Capacities of Isostructural Metal–Organic Frameworks With and Without Accessible Metal Sites: [{Zn2(abtc)(dmf)2}3] and [{Cu2(abtc)(dmf)2}3] versus [{Cu2(abtc)}3

Various metal–organic frameworks (MOFs) have been prepared to obtain materials that show specific or multifunctional properties. Porous MOFs that contain free space where guest molecules can be accommodated are of particular interest because they can be applied in gas storage and separation, selective adsorption and separation of organic molecules, ion exchange, catalysis, sensor technology, and for the fabrication of metal nanoparticles. Secondary building units (SBUs) with a specific geometry have often been employed for the modular construction of porous MOFs as they make the design and prediction of molecular architectures simple and easy. In particular, {M2(CO2)4}-type paddlewheel clusters that can be formed from the solvothermal reaction of M ions and the appropriate carboxylic acid are widely used for the construction of porous frameworks. Three-dimensional porous frameworks with various topologies (Pt3O4, boracites, NbO, and PtS nets) can be built from paddlewheel-type metal cluster SBUs and trior tetracarboxylates, whereas pillared square-grid networks can be constructed from paddlewheel cluster SBUs and dicarboxylates in the presence of diamine ligands. Porous MOFs with accessible metal sites (AMSs) should have a higher hydrogen storage capacity than those without AMSs, although there are not yet enough experimental data to support this assumption. To determine the effect of AMSs in a MOF on H2 adsorption, the H2 uptakes should be compared for the same framework in the absence and presence of AMSs, or for two independent isostructural MOFs with and without AMSs. H2 uptake has previously been measured under several different outgassing conditions. Unfortunately, these experiments could not clearly demonstrate the effect of AMSs as the exact formula and structure at each stage were not known. Furthermore, even when coordinating solvent molecules are successfully removed with retention of the porous framework structure, the metal ion sometimes transforms its coordination geometry to the thermodynamically most stable form instead of keeping the AMSs. Herein we report two porous MOFs with the same NbOtype net topology, namely [{Zn2(abtc)(dmf)2}3]·4H2O·10dmf (1) and [{Cu2(abtc)(H2O)2}3]·10dmf·6 (1,4-dioxane) (2 ; H4abtc= 1,1’-azobenzene-3,3’,5,5’-tetracarboxylic acid ), and compare the gas adsorption data for the MOFs with and without AMSs. Heating crystals of 1 and 2 under precisely controlled conditions allowed us to prepare [{Zn2(abtc)(dmf)2}3] (1a ; SNU-4) and [{Cu2(abtc)(dmf)2}3] (2a ; SNU-5’), which have no AMSs, as well as [{Cu2(abtc)}3] (2b ; SNU-5), which has AMSs. The framework structure of 1a is the same as that of 1 and those of 2a and 2b are the same as that of 2, as evidenced by the PXRD patterns. Solid 1a, 2a, and 2b exhibit higher adsorption capabilities for N2, CO2, CH4, and H2 than other previously reported MOFs. In particular, 2b adsorbs 2.87 wt% of H2 gas at 77 K and 1 atm, which is the highest value for H2 sorption under these conditions amongst a variety of other MOFs. The N2, CO2, and CH4 adsorption capacities per unit sample volume for 2b, which has AMSs, are 140–160% higher than those for 1a and 2a, which have no AMSs. The H2 adsorption capacity of 2b is also higher than those of 1a and 2a [at 77 K and 1 atm, 2.87 wt% for 2b vs. 2.07 wt% for 1a and 1.83 wt% for 2a ; excess adsorbed H2 at 77 K and 50 bar: 5.22 wt% (total 6.76 wt%) for 2b vs. 3.70 wt% (total 4.49 wt%) for 1a], although this is mainly due to the lower molecular weight effect of 2b. The H2 sorption capacity ratios 2b/1a and 2b/2a per unit sample volume at 77 K and 1 atm are 105% and 120%, respectively, and the ratio 2b/1a at 77 K and 50 bar is 106%. Our measurements of the isosteric heat of H2 adsorption (zero-coverage isosteric heats are 7.24, 6.53, and 11.60 kJmol for 1a, 2a, and 2b, respectively) suggest that the enhanced H2 adsorption in 2b can be attributed to the stronger interaction of H2 molecules with the AMSs of the MOF. Yellowish block-shaped crystals of [{Zn2(abtc)(dmf)2}3]·4H2O·10dmf (1) were prepared by heating a dmf solution of Zn(NO3)2·6H2O and H4abtc at 100 8C for 12 h. Greenish block-shaped crystals of [{Cu2(abtc)(H2O)2}3]·10dmf·6 (1,4-dioxane) (2) were prepared by heating Cu(NO3)2·xH2O and H4abtc in a dmf/1,4-dioxane/H2O (4:3:1 v/v) mixture at 80 8C for 24 h. Solid 1 is insoluble in common organic solvents but is slightly soluble in water, where it dissociates into its building blocks. Solid 2 is insoluble in all common organic solvents and water. The temperaturedependent PXRD patterns show that the framework struc[*] Y.-G. Lee, H. R. Moon, Y. E. Cheon, Prof. M. P. Suh Department of Chemistry, Seoul National University Seoul 151-747 (Republic of Korea) Fax: (+82)2-886-8516 E-mail: mpsuh@snu.ac.kr