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High-throughput screening of small-molecule adsorption in MOF  [PDF]
Pieremanuele Canepa,Calvin A. Arter,Eliot M. Conwill,Daniel H. Johnson,Brian A. Shoemaker,Karim Z. Soliman,T. Thonhauser
Physics , 2013, DOI: 10.1039/C3TA12395B
Abstract: Using high-throughput screening coupled with state-of-the-art van der Waals density functional theory, we investigate the adsorption properties of four important molecules, H_2, CO_2, CH_4, and H_2O in MOF-74-M with M = Be, Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Zr, Nb, Ru, Rh, Pd, La, W, Os, Ir, and Pt. We show that high-throughput techniques can aid in speeding up the development and refinement of effective materials for hydrogen storage, carbon capture, and gas separation. The exploration of the configurational adsorption space allows us to extract crucial information concerning, for example, the competition of water with CO_2 for the adsorption "pockets." We find that only a few noble metals---Rh, Pd, Os, Ir, and Pt---favor the adsorption of CO_2 and hence are potential candidates for effective carbon-capture materials. Our findings further reveal significant differences in the binding characteristics of H_2, CO_2, CH_4, and H_2O within the MOF structure, indicating that molecular blends can be successfully separated by these nano-porous materials.
Synthesis, Characterization and Adsorption Capability of MOF-5  [PDF]
N. Iswarya,M.G. Kumar,K.S. Rajan,R.J.B. Balaguru
Asian Journal of Scientific Research , 2012,
Abstract: Metal Organic Frameworks (MOF) are three dimensional organic-inorganic hybrid crystalline materials where a metal containing inorganic cluster is coordinated to a polydentate organic ligand. MOF-5 consists of Zn4O inorganic moiety, that acts as secondary building unit, coordinating to benzene 1,4-dicarboxylate, a bidentate ligand that acts as spacers, to form a three dimensional structure. We report the synthesis of MOF-5 using zinc nitrate and terephthalic acid as precursors dissolved in dimethyl formamide. The synthesized MOF-5 has been characterized using Fourier Transform Infrared Spectroscopy, X-ray diffractometry, Thermal analysis, Scanning Electron Microscopy and Transmission Electron Microscopy. Surface morphology reveals well-ordered structures with large number of pores in meso-scale. Adsorption capability towards vapours and gases has been studied using ethanol and CO2 as the model vapours using a chemi-resistive approach. Present results indicate that MOF-5 is a promising candidate for CO2 sequestration and gas storage.
Direct Observation of Hydrogen Adsorption Sites and Nano-Cage Formation in Metal-Organic Frameworks (MOF)  [PDF]
T. Yildirim,M. R. Hartman
Physics , 2005, DOI: 10.1103/PhysRevLett.95.215504
Abstract: The hydrogen adsorption sites in MOF5 were determined using neutron powder diffraction along with first-principles calculations. The metal-oxide cluster is primarily responsible for the adsorption while the organic linker plays only a secondary role. Equally important, at low temperatures and high-concentration, H2 molecules form unique interlinked high-symmetry nano-clusters with intermolecular distances as small as 3.0 Ang. and H2-uptake as high as 10-wt%. These results hold the key to optimizing MOF materials for hydrogen storage applications and also suggest that MOFs can be used as templates to create artificial interlinked hydrogen nano-cages with novel properties.
X-Nuclei NMR Self-Diffusion Studies in Mesoporous Silica Foam and Microporous MOF CuBTC  [PDF]
Stefan Schlayer,Anne-Kristin Pusch,Friederike Pielenz,Steffen Beckert,Mikulá? Peksa,Carsten Horch,Lutz Moschkowitz,Wolf-Dietrich Einicke,Frank Stallmach
Materials , 2012, DOI: 10.3390/ma5040617
Abstract: A standard X-observe NMR probe was equipped with a z-gradient coil to enable high-sensitivity pulsed field gradient NMR diffusion studies of Li + and Cs + cations of aqueous salt solutions in a high-porosity mesocellular silica foam (MCF) and of CO 2 adsorbed in metal-organic frameworks (MOF). The coil design and the necessary probe modifications, which yield pulsed field gradients of up to ±16.2Tm ?1, are introduced. The system was calibrated at 2H resonance frequency and successfully applied for diffusion studies at 7Li, 23Na, 13C and 133Cs frequencies. Significant reductions of the diffusivities of the cations in LiCl ac and CsCl ac solution introduced into MCFs are observed. By comparison of the diffusion behavior with the bulk solutions, a tortuosity of the silica foam of 4.5 ± 0.6 was derived. Single component self-diffusion of CO 2 and CH 4 (measured by 1H NMR) as well as self-diffusion of the individual components in CO 2/CH 4 mixtures was studied in the MOF CuBTC. The experimental results confirm high mobilities of the adsorbed gases and trends for diffusion separation factors predicted by MD simulations.
Competitive co-adsorption of CO2 with H2O, NH3, SO2, NO, NO2, N2, O2, and CH4 in M-MOF-74 (M= Mg, Co, Ni): the role of hydrogen bonding  [PDF]
Kui Tan,Sebastian Zuluaga,Qihan Gong,Yuzhi Gao,Nour Nijem,Jing Li,Timo Thonhauser,Yves J Chabal
Physics , 2015, DOI: 10.1021/acs.chemmater.5b00315
Abstract: The importance of co-adsorption for applications of porous materials in gas separation has motivated fundamental studies, which have initially focused on the comparison of the binding energies of different gas molecules in the pores (i.e. energetics) and their overall transport. By examining the competitive co-adsorption of several small molecules in M-MOF-74 (M= Mg, Co, Ni) with in-situ infrared spectroscopy and ab initio simulations, we find that the binding energy at the most favorable (metal) site is not a sufficient indicator for prediction of molecular adsorption and stability in MOFs. Instead, the occupation of the open metal sites is governed by kinetics, whereby the interaction of the guest molecules with the MOF organic linkers controls the reaction barrier for molecular exchange. Specifically, the displacement of CO2 adsorbed at the metal center by other molecules such as H2O, NH3, SO2, NO, NO2, N2, O2, and CH4 is mainly observed for H2O and NH3, even though SO2, NO, and NO2, have higher binding energies (~70-90 kJ/mol) to metal sites than that of CO2 (38 to 48 kJ/mol) and slightly higher than water (~60-80 kJ/mol). DFT simulations evaluate the barriers for H2O->CO2 and SO2->CO2 exchange to be - 13 and 20 kJ/mol, respectively, explaining the slow exchange of CO2 by SO2, compared to water. Furthermore, the calculations reveal that the kinetic barrier for this exchange is determined by the specifics of the interaction of the second guest molecule (e.g., H2O or SO2) with the MOF ligands.
Probing the Structure, Stability and Hydrogen Adsorption of Lithium Functionalized Isoreticular MOF-5 (Fe, Cu, Co, Ni and Zn) by Density Functional Theory  [PDF]
Natarajan Sathiyamoorthy Venkataramanan,Ryoji Sahara,Hiroshi Mizuseki,Yoshiyuki Kawazoe
International Journal of Molecular Sciences , 2009, DOI: 10.3390/ijms10041601
Abstract: Li adsorption on isoreticular MOFs with metal Fe, Cu, Co, Ni and Zn was studied using density function theory. Li functionalization shows a considerable structural change associated with a volume change in isoreticular MOF-5 except for the Zn metal center. Hydrogen binding energies on Li functionalized MOFs are seen to be in the range of 0.2 eV, which is the desired value for an ideal reversible storage system. This study has clearly shown that Li doping is possible only in Zn-based MOF-5, which would be better candidate to reversibly store hydrogen.
Generalization of the adsorption process in crystalline porous materials and its application to Metal-Organic Frameworks (MOFs)  [PDF]
Jose L. Mendoza-Cortes,Alexander A. Aduenko
Physics , 2014,
Abstract: In this paper we present an approach for the generalization of adsorption of light gases in crystalline porous materials. Our approach allows the determination of gas uptake considering only geometrical constrains of the porous framework and interaction energy of the guest molecule with the framework. The derivation of this general equation for the uptake of any crystalline porous framework is presented. Based on this theory, we calculated optimal values for the adsorption enthalpy at different temperatures and pressures. We also present the use of this theory to determine the optimal linker length for a topological equivalent framework series. We validate this theoretical approach by comparing the predicted uptake to experimental values for MOF-5, MOF-14, MOF-177, MOF-200, SNU-77H and Li-metalated MOF-177 and MOF-200. We obtained the universal equation for optimal linker length given a topology of a porous framework. This work applies the general equation to Metal-Organic Frameworks (MOFs) but it can be used for other crystalline materials such as Covalent-Organic Frameworks (COFs) and Zeolitic imidazolate frameworks (ZIFs). These results will serve to design new porous materials that exhibit high net storage capacities, in particular for molecular hydrogen.
Chiral molecule adsorption on helical polymers  [PDF]
Maria R. D'Orsogna,Tom Chou
Physics , 2003, DOI: 10.1103/PhysRevE.69.021805
Abstract: We present a lattice model for helicity induction on an optically inactive polymer due to the adsorption of exogenous chiral amine molecules. The system is mapped onto a one-dimensional Ising model characterized by an on-site polymer helicity variable and an amine occupancy one. The equilibrium properties are analyzed at the limit of strong coupling between helicity induction and amine adsorption and that of non-interacting adsorbant molecules. We discuss our results in view of recent experimental results.
Structural, elastic, thermal, and electronic response of small-molecule-loaded metal organic framework materials  [PDF]
Pieremanuele Canepa,Kui Tan,Yingjie Du,Hongbing Lu,Yves J. Chabal,T. Thonhauser
Physics , 2014, DOI: 10.1039/C4TA03968H
Abstract: We combine infrared spectroscopy, nano-indentation measurements, and \emph{ab initio} simulations to study the evolution of structural, elastic, thermal, and electronic responses of the metal organic framework MOF-74-Zn when loaded with H$_2$, CO$_2$, CH$_4$, and H$_2$O. We find that the molecular adsorption in this MOF triggers remarkable responses in all of these properties of the host material, with specific signatures for each of the guest molecules. With this comprehensive study we are able to clarify and correlate the underlying mechanisms regulating these responses with changes of the physical and chemical environment. Our findings suggest that metal organic framework materials in general, and MOF-74-Zn in particular, can be very promising materials for novel transducers and sensor applications, including highly selective small-molecule detection in gas mixtures.
A study on metal organic framework (MOF-177) synthesis, characterization and hydrogen adsorption -desorption cycles  [PDF]
V.Viditha, M.Venkateswer Rao, K.Srilatha11, V.Himabindu, Anjaneyulu Yerramilli
International Journal of Energy and Environment , 2013,
Abstract: Hydrogen has long been considered to be an ideal alternative to fossil-fuel systems and much work has now been done on its storage. There are four main methods of hydrogen storage: as a liquid; as compressed hydrogen; in the form of metal hydrides; and by physisorption. Among all the materials metal organic frameworks (MOFs) are considered to have desirable properties like high porosity, pore volume and high thermal stability. MOF-177 is considered to be an ideal storage material. In this paper we study about its synthesis and hydrogen storage capacities of MOF-177 at different pressures ranging from 25, 50, 75 and 100 bar respectively. The obtained samples are characterized by XRD, BET and SEM. The recorded results show that the obtained hydrogen capacity is 1.1, 2.20, 2.4 and 2.80 wt%. The desorption capacity is 0.9, 2.1, 2.37 and 2.7 wt% at certain temperatures like 373 K.
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