Co-reporter:Alexander S. Münch and Florian O. R. L. Mertens
CrystEngComm 2015 vol. 17(Issue 2) pp:438-447
Publication Date(Web):17 Oct 2014
DOI:10.1039/C4CE01327A
Metal–organic frameworks (MOFs) have demonstrated great utilizability in separation applications, as in the separation of small volatile compounds via gas chromatography (GC). In the present work, HKUST-1 (Hong Kong University of Science and Technology), one of the best investigated MOFs, is used as a stationary phase for the gas chromatographic separation of various analytes possessing different modes of interaction due to their differences in polarity and the presence of free electron pairs. The system was investigated by inverse gas chromatography (IGC) to demonstrate in general how MOF materials can be quantitatively and qualitatively characterized in respect to their Lewis basic and acidic properties. Applying IGC theory, the investigation of the separation problem of benzene and its completely hydrogenated analogue cyclohexane was used to the determine the donor properties of the MOF linker benzene-1,3,5-tricarboxylic acid and the separation of diethyl ether, diisopropyl ether, tetrahydrofuran, and di-n-propyl ether to determine the acceptor properties of the coordinatively unsaturated sites of the copper(II)-secondary building unit (SBU), i.e. the nodal points of the MOF lattice.
Co-reporter:Tony Böhle, Florian Mertens
Microporous and Mesoporous Materials 2015 Volume 216() pp:82-91
Publication Date(Web):1 November 2015
DOI:10.1016/j.micromeso.2015.03.019
•[Cu2(cam)2(dabco)] and [Cu2(cam)2(bipy)] based capillary columns were generated.•[Cu2(cam)2(dabco)] based capillaries enabled size dependent GC separations.•The investigated MOF based GC columns show unusual peak broadening.•A correlation between the heats of adsorption and the pore sizes was observed.Short GC capillary columns were coated with micro particles of the two isoreticular pillared-layer frameworks (PLFs) [Cu2(cam)2(dabco)] and [Cu2(cam)2(bipy)] (cam2− = (+)-camphoric acid, dabco = 1,4-diazabicyclo[2.2.2]octane, bipy = 4,4′-bipyridine) by the technique of the so called “Controlled SBU Approach”. It is demonstrated that the small pore openings of [Cu2(cam)2(dabco)] enable size dependent gas chromatographic separations which were not observed on [Cu2(cam)2(bipy)]. In some cases the interaction with the smaller pore system lead to unusual peak broadening. Both compounds offer excellent properties for the high resolution separation of light hydrocarbons including isomers. Chromatographic parameters, including resolution factors and selectivities, as well as thermodynamic data characterizing the interaction between the stationary phase and the analytes were determined from the temperature-dependent retentions times. Furthermore, isothermal measurements were used for the calculation of diffusion constants of selected analytes in the mobile phase and in the [Cu2(cam)2(dabco)] and [Cu2(cam)2(bipy)] structures.
Co-reporter:Michael Günthel;Jörg Hübscher;Rosemarie Dittrich;Edwin Weber;Yvonne Joseph;Florian Mertens
Journal of Polymer Science Part B: Polymer Physics 2015 Volume 53( Issue 5) pp:335-344
Publication Date(Web):
DOI:10.1002/polb.23633
ABSTRACT
A symmetrical 2-thiopyrimidine based molecule with an expanded π-electron system is synthesized and used to form a self-assembled monolayer (SAM) on gold surfaces. Utilizing chemical vapor deposition a monolayer of (3-mercaptopropyl)triethoxysilane is formed on silicon dioxide substrates. Both of these SAM coated substrates are characterized by X-ray photoelectron spectroscopy and the growth of a coordination polymer built up from 5,5′-(ethyne-1,2-diyl)bis(2-hydroxyacetophenone) and copper(II) on dual SAM coated transducers is studied. After the deposition procedure on interdigital electrodes the electrical properties of the polymer are investigated performing resistive measurements. A significant change of the resistance, which depends on the surrounding atmosphere, proves the sensing behavior of the synthesized coordination polymer. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 335–344
Co-reporter:Daniel Thomas, Michael Zeilinger, Daniel Gruner, Regina Hüttl, Jürgen Seidel, Anja U.B. Wolter, Thomas F. Fässler, Florian Mertens
The Journal of Chemical Thermodynamics 2015 Volume 85() pp:178-190
Publication Date(Web):June 2015
DOI:10.1016/j.jct.2015.01.004
•High quality experimental heat capacities of the new lithium rich silicides Li17Si4 and Li16.42Si4 are reported.•Two different calorimeters have been used to cover the broad temperature range from (2 to 873) K.•Samples were prepared and characterized (XRD) by the original authors who firstly described these new silicide phases in 2013.•Supply of polynomial heat capacity functions for four temperature intervals.•Calculation of standard entropies and entropies of formation of the lithium silicides.This work presents the heat capacities and standard entropies of the recently described lithium rich silicide phases Li17Si4 and Li16.42Si4 as a function of temperature in the range from (2 to 873) K. The measurements were carried out using two different calorimeters. The heat capacities were determined in the range from T = (2 to 300) K by a relaxation technique using a Physical Properties Measurement System (PPMS) from Quantum Design, and in the range from T = (283 to 873) K by means of a Sensys DSC from Setaram applying the Cp-by-step method. The experimental data are given with an accuracy of (1 to 2)% above T = 20 K and the error increases up to 7% below T = 20 K. The results of the measurements at low temperatures permit the calculation of additional thermodynamic parameters such as the standard entropy as well as the temperature coefficients of electronic and lattice contributions to the heat capacity. Additionally, differential scanning calorimetric (DSC) measurements were carried out to verify the phase transition temperatures of the studied lithium silicide phases. The results represent a significant contribution to the data basis for thermodynamic calculations (e.g. CALPHAD) and to the understanding of the phase equilibria in the (Li + Si) system, especially in the lithium rich region.
Co-reporter:Stefan Loos, Daniel Gruner, Mahmoud Abdel-Hafiez, Jürgen Seidel, Regina Hüttl, Anja U.B. Wolter, Klaus Bohmhammel, Florian Mertens
The Journal of Chemical Thermodynamics 2015 Volume 85() pp:77-85
Publication Date(Web):June 2015
DOI:10.1016/j.jct.2015.01.007
•The heat capacity of olivine-type LiFePO4 was determined in the range of T = (2 to 773) K.•The experimental data were found to be in good agreement with published theoretical calculations in a broad temperature range.•The standard entropy of LiFePO4 has been calculated taking into account the antiferromagnetic transition at T = 49.2 K.The heat capacity of olivine-type lithium iron phosphate (LiFePO4 – LFP) has been measured covering a temperature range from (2 to 773) K. Three different calorimeters were used. The Physical Property Measurement System (PPMS) from Quantum Design was applied in the range between T = (2 and 300) K, a Micro-DSC II from Setaram within the range between T = (283 and 353) K and data between T = (278 and 773) K were measured by means of a Sensys DSC (Setaram) using the Cp-by-step method. Experimental data are given with an error of (1 to 2)% above T = 20 K and up to 8% below 20 K. The data were subdivided into appropriate temperature intervals and fitted using common heat capacity functions. The low temperature results permit the calculation of standard entropies and temperature coefficients of electronic, lattice, as well as magnetic (antiferromagnetic transition at T = 49.2 K) contributions to the heat capacity. The obtained experimental values were compared to results of a recently published first principles phonon study (DFT) and to few available experimental data from the literature.
Co-reporter:Christian Reller, Matthias Pöge, Andreas Lißner, and Florian O. R. L Mertens
Environmental Science & Technology 2014 Volume 48(Issue 24) pp:14799
Publication Date(Web):November 14, 2014
DOI:10.1021/es503914d
Carbon dioxide chemically bound to alcohol-amines was hydrogenated to methanol under retrieval of these industrially used CO2 capturing reagents. The energetics of the process can be seen as a partial cancellation of the exothermic heat of reaction of the hydrogenation with the endothermic one of the CO2 release from the capturing reagent. The process provides a means to significantly improve the energy efficiency of CO2 to methanol conversions.
Co-reporter:Tony Böhle, Florian Mertens
Microporous and Mesoporous Materials 2014 Volume 183() pp:162-167
Publication Date(Web):1 January 2014
DOI:10.1016/j.micromeso.2013.09.001
•The metal–organic framework [Cu2(bdc)2(dabco)] was synthesized via controlled SBU-approach and a capillary column was coated with it.•Light hydrocarbons were separated by the [Cu2(bdc)2(dabco)]-coated column and their heats of adsorption were determined.•From kinetic investigations the relation between mass transfer and plate height was determined.The unique properties of MOFs (MOF = metal–organic framework) such as their adjustable pore size, high intrinsic surface area and organic functionalizations make them a suitable class of materials for chromatographic separations. Micro particles of [Cu2(bdc)2(dabco)] (bdc2− = terephthalate, DABCO = 1,4-diazabicyclo[2.2.2]octane) were prepared by a cyclic deposition method based on the technique of the so called “controlled SBU approach” and anchored via SAMs (SAM = self-assembled monolayer) in a short GC capillary column to generate a wall-bonded cross linked stationary phase. It could be demonstrated, that the fabricated column exhibits a high separation power for the light hydrocarbons C1–C7. Chromatographic parameters, including resolution factors and selectivity as well as thermodynamic data characterizing the interaction between the stationary phase and the analytes, were determined from the temperature-dependent measurements of the retentions times of these analytes. In addition, isothermal measurements were used for the calculation of diffusion constants in [Cu2(bdc)2(dabco)].
Co-reporter:Christian Reller ;Florian O. R. L. Mertens
European Journal of Inorganic Chemistry 2014 Volume 2014( Issue 3) pp:450-459
Publication Date(Web):
DOI:10.1002/ejic.201301253
Abstract
The catalytic hydrodechlorination of BCl3 with molecular hydrogen in the presence of tertiary amines is a viable strategy for the energy-efficient generation of valuable B–H bonds. A mechanistic study based on experiments with isolated intermediates and deuterium labeling experiments is presented. The occurrence of the rate-limiting reverse reaction from the insoluble Et3NHCl adduct was identified as a major cause of low Et3NBH3 yields. In addition, amines with NCH2 units, which also serve in the corresponding cases as solvents, have a strong influence on the reaction kinetics; they are directly involved in the hydrogen transfer at elevated temperatures and assume the role of a cocatalyst. A catalytic cycle for the reaction on a nickel boride catalyst is proposed.
Co-reporter:Alexander S. Münch, Felix Katzsch, Tobias Gruber, Florian O.R.L. Mertens
Journal of Molecular Structure 2014 1074() pp: 542-548
Publication Date(Web):25 September 2014
DOI:10.1016/j.molstruc.2014.06.035
•Bromotrimesic acid (1) and bromotrimesic trimethyl ester (2) were synthesised.•Single crystal structures were determined to study supramolecular interactions.•The 1:1 inclusion compound of 1 with water has been investigated by IR spectroscopy and TG-DSC measurements.Two analogues of the well investigated trimesic acid viz. the 2-bromobenzene-1,3,5-tricarboxylic acid 1 and their ester trimethyl 2-bromobenzene-1,3,5-tricarboxylate 2, have been synthesised and their X-ray structures were solved. Acid 1 crystallises as 1:1 inclusion compound with water in a layer structure. Like in the solid state structure of trimesic acid, we found strong OH⋅⋅⋅O hydrogen bonds between one of the carboxyl groups and a neighbouring molecule to form a hydrogen bonding motif R22(8). Additionally, a water molecule and a second acid function of 1 are involved in further hydrogen bonding featuring the graph set R44(12) forming what might be called a water inserted dimer. As shown by TG-DSC measurements the water molecule in the 1:1 inclusion compound of 1 is engaged in two strong OH⋅⋅⋅O hydrogen bonds, it escapes at a rather low temperature of 99 °C. Bromine monosubstitution at the benzene ring forces the third carboxylic acid out of the mean plane of the molecule, which disturbs the coplanar arrangement of the three COOH moieties. Thus, the typical “chicken-wire” network formation is hindered. In the trimethyl 2-bromobenzene-1,3,5-tricarboxylate (2), the formation of strong OH⋅⋅⋅O hydrogen bonds is disabled by esterification of the acid functions. Nevertheless, the packing of 2 features solvent free molecular layers formed by Br⋅⋅⋅O contacts and connected van der Waals interactions. These layers are linked to each other by inverse bifurcated hydrogen bonds in term weak CH⋅⋅⋅O contacts. The results of the X-ray analysis could be confirmed by infrared spectroscopy.
Co-reporter:Felix Katzsch, Alexander S. Münch, Florian O.R.L. Mertens, Edwin Weber
Journal of Molecular Structure 2014 1064() pp: 122-129
Publication Date(Web):5 May 2014
DOI:10.1016/j.molstruc.2014.01.080
•Three new alcohol coordinated copper(II) benzoate paddle wheels have been prepared.•The structures of the compounds are determined by single crystal X-ray diffraction.•The structures with different alcohols have been investigated by a systematic study.Three new copper(II) benzoates coordinated by 1-propanol, [Cu2(PhCOO)4(1-PrOH)2] [Cu2(PhCOO)4(H2O)2] (3), 1-butanol, [Cu2(PhCOO)4(1-BuOH)2] (4) and 1-pentanol, [Cu2(PhCOO)4(1-PentOH)2] (5) at the available metal coordination sites, have been prepared and investigated with reference to their X-ray crystal structures. In all cases, dimeric paddle-wheel complexes where two copper(II) ions are held together by four benzoates were found. Moreover, the complexes show 1-propanol and water (3), 1-butanol (4) and 1-pentanol (5) coordinated to the free coordination sites of the Cu(II) ions. The dimeric complex units are connected with each other by strong OH⋯O hydrogen bonds to form strands linked together via weaker CH⋯O and CH⋯π interactions. Comparative discussion including the redetermined crystal structures obtained from copper(II) benzoate in the presence of methanol (1) or ethanol (2) allows to draw argumentation regarding the coordination of linear alcohols in corresponding crystals of paddle-wheel complexes.Graphical abstract
Co-reporter:Alexander S. Münch, Felix Katzsch, Edwin Weber, Florian O.R.L. Mertens
Journal of Molecular Structure 2013 Volume 1043() pp:103-108
Publication Date(Web):5 July 2013
DOI:10.1016/j.molstruc.2013.04.005
•A new extended analogue of trimesic acid has been prepared.•The structure of the compound is determined by single crystal X-ray diffraction.•A new hydrogen bond motif of graph set R43(12) was obtained.The new 1,3,5-trisubstituted benzene derivative 1 featuring three propiolic acid side arms symmetrically attached to a benzene core has been synthesized. Spectroscopic studies including 1H and 13C NMR as well as FTIR measurements were performed. The single crystal structure of 1 shows involvement of a water molecule giving rise to formation of a new 12-membered hydrogen bonded ring motif of graph set R43(12) while the packing is typically interspersed with channel-like voids of different dimension containing additional ethanol and water molecules which, however, could not be localized precisely.
Co-reporter:Alexander S. Münch and Florian O. R. L. Mertens
Journal of Materials Chemistry A 2012 vol. 22(Issue 20) pp:10228-10234
Publication Date(Web):13 Feb 2012
DOI:10.1039/C2JM15596F
The development of cyclic preparation techniques based on the application of an SBU (secondary building unit) precursor and a linker solution for the generation of MOF (metal–organic framework) coatings were used to prepare HKUST-1 (Hong Kong University of Science and Technology-1) coated capillary gas-chromatographic columns. As a prerequisite for the conducted preparation of the coatings some optimisation of the procedure for the generation of the MOF material at room temperature was carried out. Beside the demonstration of their general suitability for the separation of permanent gases, the capillaries were used to perform isothermal retention time measurements with analytes possessing electron donating capabilities, such as aromatic or oxygen containing compounds. Since HKUST-1 possesses SBUs with open metal sites, the heat of adsorption and the adsorption entropy were determined to address the question whether or not coordinative contributions may affect the analyte–MOF interaction.
Co-reporter:Johannes F. Kostka;René Schellenberg;Felix Baitalow;Tom Smolinka;Florian Mertens
European Journal of Inorganic Chemistry 2012 Volume 2012( Issue 1) pp:
Publication Date(Web):
DOI:10.1002/ejic.201190112
Co-reporter:Johannes F. Kostka;René Schellenberg;Felix Baitalow;Tom Smolinka;Florian Mertens
European Journal of Inorganic Chemistry 2012 Volume 2012( Issue 1) pp:49-54
Publication Date(Web):
DOI:10.1002/ejic.201100795
Abstract
The dehydrogenation reaction of the hydrogen-storage compound ammonia–borane (AB) dissolved in triglyme (TG) reveals an unexpected but favourable concentration dependence of its dehydrogenation behaviour. Formal reaction-order considerations and 11B NMR spectroscopic analytics point towards a complex AB decomposition and hydrogen-release scheme that in highly concentrated solutions partly begins to resemble that of the solid-state case. The analysis of the gas-release characteristics identified two hydrogen desorption events that display an increasing peak overlap with increasing initial AB concentration. 11B NMR spectroscopic studies indicate that the concentration-dependent stability of the intermediate diammoniate of diborane, the presence of which appears to influence the rates of several dehydrogenation steps by interacting with various other intermediates, is one of the key factors for the overall hydrogen release.
Co-reporter:Alexander S. Münch, Maria S. Lohse, Steffen Hausdorf, Gerhard Schreiber, Denise Zacher, Roland A. Fischer, Florian O.R.L. Mertens
Microporous and Mesoporous Materials 2012 Volume 159() pp:132-138
Publication Date(Web):1 September 2012
DOI:10.1016/j.micromeso.2012.04.023
As a representative of the IRMOF series, MOF-5 was deposited onto self-assembled monolayer modified metal and fused silica surfaces applying the controlled SBU approach (CSA) (SBU – secondary building unit). Although the controlled SBU approach was already used in some cases to deposit IRMOFs and other MOF (metal–organic framework) types on surfaces, this contribution is the first study concerned with basic processes of the deposition of IRMOFs onto SAM (self-assembled monolayers) coated substrates, like the carboxylate exchange between SBU precursor and SAM, the influence of different substrates, or the morphology differences resulting from different cyclic preparation procedures.The deposition of the first SBU layer (basic zinc perfluoromethylbenzoate) onto the surface and the carboxylate exchange during CSA was demonstrated by infrared reflection–absorption spectroscopy. The various aspects of the MOF deposition, such as the crystalline growth, the element distribution, the porosity, and the morphology of the thin films were addressed by powder X-ray diffraction (PXRD), energy-dispersive X-ray spectroscopy (EDX), nitrogen cryo-adsorption measurement, and scanning electron microscopy (SEM).Graphical abstractRecently developed procedures for the coating of surfaces with metal-organic frameworks using cyclic preparation schemes in which different reactants are supplied in alternate manner result in very different morphologies of the coatings depending on the intermediate removal of reactants stored in the pores of the just grown MOF material between the different preparation cycles.Highlights► Growth of MOF-5 on copper, gold and fused silica generated by cyclic preparation techniques (CSA). ► Demonstration of the attachment of the first SBU layer on SAM covered surfaces via FTIR tracing. ► The surface storage effect and its influence on the morphology of MOF coatings.
Co-reporter:Christian Reller ;Dr. Florian O. R. L. Mertens
Angewandte Chemie International Edition 2012 Volume 51( Issue 47) pp:11731-11735
Publication Date(Web):
DOI:10.1002/anie.201201134
Co-reporter:Christian Reller ;Dr. Florian O. R. L. Mertens
Angewandte Chemie 2012 Volume 124( Issue 47) pp:11901-11905
Publication Date(Web):
DOI:10.1002/ange.201201134
Co-reporter:Alexer S. Münch;Dr. Jürgen Seidel;Anja Obst;Dr. Edwin Weber;Dr. Florian O. R. L. Mertens
Chemistry - A European Journal 2011 Volume 17( Issue 39) pp:10958-10964
Publication Date(Web):
DOI:10.1002/chem.201100642
Abstract
Recently developed MOF surface-coating techniques, the controlled SBU approach (CSA) for the generation of MOF-5, and the use of self-assembled monolayers have been combined to generate a wall-bonded, crosslinked stationary phase for gas chromatographic capillary columns displaying excellent performance in the separation of natural gas components. The chromatographic performance of this new type of column has been compared to the state-of-the-art solution for this separation problem, namely a coated silica column of the porous layer open tubular (PLOT) type. Chromatographic parameters such as separation, resolution, and tailing factors, as well as plate numbers and heights in the case of isothermal operation, have been determined. Kinetic and thermodynamic parameters characterizing the analyte–stationary phase interaction have been determined for various C1–C4 analytes.
Co-reporter:Steffen Hausdorf ; Felix Baitalow ; Tony Böhle ; David Rafaja ;Florian O. R. L. Mertens
Journal of the American Chemical Society 2010 Volume 132(Issue 32) pp:10978-10981
Publication Date(Web):July 27, 2010
DOI:10.1021/ja1028777
A simple two-component procedure was developed to synthesize not only classical zinc-based IRMOFs represented by MOF-5 but also the cobalt and beryllium homologues of this most prominent MOF. The procedure is the first manifestation of mirroring the IRMOF series with other metal centers taken from main-group as well as transition-metal elements. Because of the existence of many suitable precursors, the procedure promises the generation of a large number of IRMOF homologues. Since the IRMOF series together with the MIL series is the MOF group with the largest number of representatives, the possibility of choosing the metal centers of the secondary building units from an extended set will tremendously expand the number of obtainable structures in a predictive, crystal-engineering-type way. Use of metal centers other than zinc will allow the addition of new features to the existing IRMOF structures, such as magnetic properties in the example of cobalt.
Co-reporter:Steffen Hausdorf, Wilhelm Seichter, Edwin Weber and Florian O. R. L. Mertens
Dalton Transactions 2009 (Issue 7) pp:1107-1113
Publication Date(Web):28 Nov 2008
DOI:10.1039/B813532K
An ethynylene diisophthalic acid linker molecule was synthesized and used to form a zinc carboxylate-based metal organic framework (MOF) with very large pores and unit cell volume resulting from the unusual combination of structurally different inorganic units forming the secondary building blocks (SBUs). The structure is the first zinc hydroxide carboxylate structure where the inorganic units do not form layers or ribbons but isolated islands. The structure forms true pores with a significantly narrowed pore entry similar to zeolites. The pores are, thus, not created simply by intersecting channels as in most other MOF structures. Although the pore shape is highly asymmetric the spherical free volume is with 10.8 Å still large. The stability of the SBUs in respect to exchange and removal of coordinated solvent molecules is investigated.
Co-reporter:Florian O. Mertens
Surface Science 2009 Volume 603(10–12) pp:1979-1984
Publication Date(Web):1 June 2009
DOI:10.1016/j.susc.2008.10.054
Recently developed Metal Organic Frameworks (MOFs) are the materials with the highest intrinsic surface areas to date and their discovery increased the research activity in the field of microporous adsorption materials significantly. In this contribution, a generic method of analysis for volumetrically measured adsorption isotherms is presented that separates absolute adsorption from excess adsorption to the best possible degree by representing the absolute adsorption isotherm by a superposition of in respect to pressure strictly monotonously increasing fitting function. The procedure allows to determine the heat of adsorption at constant gas uptake via implicitly defined quantities. The method was applied to adsorption data of hydrogen on MOF-5 ranging from 40 K to 200 K. Methane adsorption on MOF-5 was used to demonstrate that the common practice of neglecting the difference between excess and absolute adsorption leads to erroneously increased heat of adsorption values at high coverages and temperatures.
Co-reporter:Steffen Hausdorf, Felix Baitalow, Gert Wolf, Florian O.R.L. Mertens
International Journal of Hydrogen Energy 2008 Volume 33(Issue 2) pp:608-614
Publication Date(Web):January 2008
DOI:10.1016/j.ijhydene.2007.10.035
Ammonia borane BH3NH3BH3NH3 has attracted considerable interest in the last years as a hydrogen source material due to its high hydrogen content of 19.6 wt%. The release of hydrogen from solid ammonia borane leads to the formation of polymeric waste products. In order to make ammonia borane a promising material for applications in the hydrogen economy, an energy-efficient procedure for the regeneration of BH3NH3BH3NH3 from these waste products should be developed. A concept for such a procedure is outlined. The proposed recycling strategy is described by a self-contained reaction scheme, in which only BNH-waste and molecular hydrogen are consumed. The key step in this strategy is the hydrodechlorination of a BCl3·BCl3·base adduct with molecular hydrogen in the presence of the base in excess. The base used is only an auxiliary reactant and can be recovered in principle by the thermal decomposition of the obtained base··HCl adduct. The criteria for a proper selection of the base, which is the critical parameter for the development of an energy-efficient regeneration procedure, are discussed.
Co-reporter:Steffen Hausdorf, Jörg Wagler, Regina Moβig and Florian O. R. L. Mertens
The Journal of Physical Chemistry A 2008 Volume 112(Issue 33) pp:7567-7576
Publication Date(Web):July 25, 2008
DOI:10.1021/jp7110633
The contributions of terephthalic acid and Zn2+-coordinated water in N,N-diethylformamide (DEF) to the overall proton activity in the synthesis of MOF-5 (Zn4O(BDC)3, BDC = 1,4-benzenedicarboxylate) were quantitatively determined by combined electrochemical and UV−vis spectroscopic measurements. Structural transformations of zinc carboxylate-based metal organic frameworks due to their exposure to environments with variable water concentrations and the chemical means necessary to revert these transitions have been investigated. It was found that the water-induced structural transition of MOF-5 to the hydroxide structure Zn3(OH)2(BDC)2·2DEF (MOF-69c) can be reverted by a thermal treatment of the obtained compound and its subsequent exposure to anhydrous DEF. MOF-5 syntheses from simple carboxylates as well as a water-free synthesis based on nitrate decomposition are presented. The latter demonstrates that nitrate can serve as the sole source for the oxide ion in MOF-5.
Co-reporter:Daniel Thomas, Nadine Bette, Franziska Taubert, Regina Hüttl, Jürgen Seidel, Florian Mertens
Journal of Alloys and Compounds (15 May 2017) Volume 704() pp:
Publication Date(Web):15 May 2017
DOI:10.1016/j.jallcom.2017.02.010
•Hydrogenation pressures of Li7Si3 and Li12Si7 were measured at three temperatures.•Application of the Van't Hoff method led to large errors in derived heats of formation.•Linking of equilibrium pressures with Cp and entropy significantly reduced the error.•Standard enthalpies of formation for Li7Si3 and Li12Si7 with an error <2% are reported.This work focuses on the determination of the standard molar enthalpies of formation ΔfH°(298) of the lithium silicides Li7Si3 and Li12Si7. For this purpose the hydrogenation/dehydrogenation equilibria in the system Li-Si-H were investigated at three different temperatures (450 °C, 475 °C, 500 °C) using a Sieverts type apparatus. The measurements are based on two different sample types: (i) pure silicide Li7Si3 (Li2.33Si) and (ii) a stoichiometric mixture of lithium hydride and silicon in the ratio of Li:Si = 2.33:1. The calculation of the standard enthalpies of formation by using the slopes of the classical Van't Hoff plot results in uncertainties of at least 10%. Due to this relatively large error, an alternative evaluation method based on the linking of the hydrogen equilibrium pressures peq(H2) from the sorption measurements with recently published precise heat capacity and entropy data of the lithium silicides was applied. The obtained values for the standard enthalpy of formation amount to ΔfH°(298) = (−25.3 ± 0.3) kJ/(mol atom) for Li7Si3 and ΔfH°(298) = (−23.5 ± 0.3) kJ/(mol atom) for Li12Si7 exhibiting strongly reduced uncertainties.
Co-reporter:Steffen Hausdorf, Wilhelm Seichter, Edwin Weber and Florian O. R. L. Mertens
Dalton Transactions 2009(Issue 7) pp:NaN1113-1113
Publication Date(Web):2008/11/28
DOI:10.1039/B813532K
An ethynylene diisophthalic acid linker molecule was synthesized and used to form a zinc carboxylate-based metal organic framework (MOF) with very large pores and unit cell volume resulting from the unusual combination of structurally different inorganic units forming the secondary building blocks (SBUs). The structure is the first zinc hydroxide carboxylate structure where the inorganic units do not form layers or ribbons but isolated islands. The structure forms true pores with a significantly narrowed pore entry similar to zeolites. The pores are, thus, not created simply by intersecting channels as in most other MOF structures. Although the pore shape is highly asymmetric the spherical free volume is with 10.8 Å still large. The stability of the SBUs in respect to exchange and removal of coordinated solvent molecules is investigated.
Co-reporter:Alexander S. Münch and Florian O. R. L. Mertens
Journal of Materials Chemistry A 2012 - vol. 22(Issue 20) pp:NaN10234-10234
Publication Date(Web):2012/02/13
DOI:10.1039/C2JM15596F
The development of cyclic preparation techniques based on the application of an SBU (secondary building unit) precursor and a linker solution for the generation of MOF (metal–organic framework) coatings were used to prepare HKUST-1 (Hong Kong University of Science and Technology-1) coated capillary gas-chromatographic columns. As a prerequisite for the conducted preparation of the coatings some optimisation of the procedure for the generation of the MOF material at room temperature was carried out. Beside the demonstration of their general suitability for the separation of permanent gases, the capillaries were used to perform isothermal retention time measurements with analytes possessing electron donating capabilities, such as aromatic or oxygen containing compounds. Since HKUST-1 possesses SBUs with open metal sites, the heat of adsorption and the adsorption entropy were determined to address the question whether or not coordinative contributions may affect the analyte–MOF interaction.
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![Cobalt, tris[μ-[1,4-benzenedicarboxylato(2-)-κO1:κO'1]]-μ -oxotetra-](/data/chemimg/3800300/916459-12-6_b.png)