Clusters produced in simulations of MOF assembly at metal : ligand ratios of (a) 5 : 1 and (b) 1 ... more Clusters produced in simulations of MOF assembly at metal : ligand ratios of (a) 5 : 1 and (b) 1 : 1 with identical interaction potentials.
The paper describes the first sequence of the Skarstrom cycle for bed 1 to analyze the breackthro... more The paper describes the first sequence of the Skarstrom cycle for bed 1 to analyze the breackthrough curves and studies the importance of mass transfer resistance for the performance of the PSA process which separates a feed stream consisting of equimolar fractions of methane and ethane. The diffusivities and adsorption isotherms are calculated by molecular simulation approaches.
Cancer remains hard to treat, partially due to the non-specificity of chemotherapeutics. Metal–or... more Cancer remains hard to treat, partially due to the non-specificity of chemotherapeutics. Metal–organic frameworks (MOFs) are promising carriers for targeted chemotherapy, yet, to date, there have been few detailed studies to systematically enhance drug loading while maintaining controlled release. In this work, we investigate which molecular simulation methods best capture the experimental uptake and release of cisplatin from UiO-66 and UiO-66(NH2). We then screen a series of biocompatible, pH-sensitive zeolitic imidazolate frameworks (ZIFs) for their ability to retain cisplatin in healthy parts of the patient and release it in the vicinity of a tumor. Pure-component GCMC simulations show that the maximum cisplatin loading depends on the pore volume. To achieve this maximum loading in the presence of water, either the pore size needs to be large enough to occupy both cisplatin and its solvation shell or the MOF–cisplatin interaction must be more favorable than the cisplatin–shell in...
Zinc(ii) and zirconium(iv) MOFs show uptake and slow release of the ant alarm pheromones 3-octano... more Zinc(ii) and zirconium(iv) MOFs show uptake and slow release of the ant alarm pheromones 3-octanone and 4-methyl-3-heptanone.
... Jennifer J. Williams ... Diamine-grafted SBA-15 was reported to show an enhanced adsorption c... more ... Jennifer J. Williams ... Diamine-grafted SBA-15 was reported to show an enhanced adsorption capacity of 44 mg/g.(27) Harlick et al.(28, 29) and Serna-Guerrero et al.(30) grafted 3-[2-(2-aminoethylamino)ethylamino]propyl trimethoxysilane onto MCM-41 and pore-expanded ...
A wide variety of new nanoporous metal-organic materials are being synthesized by many research g... more A wide variety of new nanoporous metal-organic materials are being synthesized by many research groups using supramolecular chemistry and directed assembly in a building block approach based on corner units and linker molecules. These materials may lead to ...
The isosteric enthalpy of adsorption for neopentane at relative pressures down to 3 × 10(-8) in M... more The isosteric enthalpy of adsorption for neopentane at relative pressures down to 3 × 10(-8) in MCM-41 was predicted for the temperature range from -15 to 0 °C. At such low pressures and temperatures, experimental measurements become problematic for this system. We used an atomistic model for MCM-41 obtained by means of a kinetic Monte Carlo method mimicking the synthesis of the material. The model was parametrized to represent experimental nitrogen adsorption isotherms at 77 K using grand canonical Monte Carlo simulations. The simulated isosteric enthalpy of adsorption shows very good agreement with available experimental data, demonstrating that GCMC simulations can predict heats of adsorption for conditions that are challenging for experimental measurements. Additional insights into the adsorption mechanisms, derived from energetic analysis at the molecular level, are also presented.
Grand canonical Monte Carlo simulations were performed to predict adsorption isotherms for hydrog... more Grand canonical Monte Carlo simulations were performed to predict adsorption isotherms for hydrogen in a series of 10 isoreticular metal-organic frameworks (IRMOFs). The results show acceptable agreement with the limited experimental results from the literature. The effects of surface area, free volume, and heat of adsorption on hydrogen uptake were investigated by performing simulations over a wide range of pressures on this set of materials, which all have the same framework topology and surface chemistry but varying pore sizes. The results reveal the existence of three adsorption regimes: at low pressure (loading), hydrogen uptake correlates with the heat of adsorption; at intermediate pressure, uptake correlates with the surface area; and at the highest pressures, uptake correlates with the free volume. The accessible surface area and free volume, calculated from the crystal structures, were also used to estimate the potential of these materials to meet gravimetric and volumetric targets for hydrogen storage in IRMOFs.
... Studies in Surface Science and Catalysis 160 PL Llewellyn, F. Rodriquez-Reinoso, J. Rouqerol ... more ... Studies in Surface Science and Catalysis 160 PL Llewellyn, F. Rodriquez-Reinoso, J. Rouqerol and N. Seaton (Editors) .9 ... King's Buildings, Edinburgh, EH9 3JL, UK b Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston ...
ABSTRACT Two Co2+ metal-organic framework materials, constructed from a combination of 1,4-benzen... more ABSTRACT Two Co2+ metal-organic framework materials, constructed from a combination of 1,4-benzenedicarboxylate (BDC) and either 2,2′-dipyridyl-N-oxide (DPNO) or 2,2′-dipyridyl-N,N′-dioxide (DPNDO), are synthesized under solvothermal reaction conditions, and their structures solved by single crystal X-ray diffraction. Both have three-dimensional structures that contain octahedral Co2+ centers with μ2-(η2)-BDC, and bidentate DPNO or DPNDO coligands that bridge pairs of metal centers but do not contribute toward the overall connectivity of the framework. Co3(BDC)3(DPNO)2 contains trimers of trans corner-shared Co-centered octahedra with one type of bridging BDC ligand forming terminal edges of the trimers, bridging to neighboring trimer units, and a second type, bridging pairs of metals and also connecting neighboring trimers. Co2(BDC)2(DPNDO) is constructed from one-dimensional inorganic chains consisting of cis- and trans-corner shared Co2+-centered octahedra. The DPNDO ligand is bis-bidentate, forming the edges of one type of octahedron and the trans corners of the second type, with the coordination for both octahedra completed by bridging BDC linkers, which in turn connect the inorganic chains to yield a three-dimensional structure. Thermogravimetric analysis shows both materials contain trapped solvent, and while Co3(BDC)3(DPNO)2 is unstable with respect to solvent loss, Co2(BDC)2(DPNDO), and its magnesium analogue, can be desolvated to yield permanently porous materials that show thermal stability up to 300 °C. For Co2(BDC)2(DPNDO), gas adsorption studies show permanent microporosity with moderate uptake of small gas molecules (N2, CO2, CH4, and C2H6), supported by Grand Canonical Monte Carlo calculations based on the assumption of rigid crystal structures, while gravimetric analysis shows rapid and reversible methanol adsorption at ambient pressure for both the Co and Mg analogues of the framework.
Journal of the American Chemical Society, Nov 22, 2006
A new three-dimensional chromium(III) naphthalene tetracarboxylate, CrIII3O(H2O)2F{C10H4(CO2)4}1.... more A new three-dimensional chromium(III) naphthalene tetracarboxylate, CrIII3O(H2O)2F{C10H4(CO2)4}1.5.6H2O (MIL-102), has been synthesized under hydrothermal conditions from an aqueous mixture of Cr(NO3)3.9H2O, naphthalene-1,4,5,8-tetracarboxylic acid, and HF. Its structure, solved ab initio from X-ray powder diffraction data, is built up from the connection of trimers of trivalent chromium octahedra and tetracarboxylate moieties. This creates a three-dimensional structure with an array of small one-dimensional channels filled with free water molecules, which interact through hydrogen bonds with terminal water molecules and oxygen atoms from the carboxylates. Thermogravimetric analysis and X-ray thermodiffractometry indicate that MIL-102 is stable up to approximately 300 degrees C and shows zeolitic behavior. Due to topological frustration effects, MIL-102 remains paramagnetic down to 5 K. Finally, MIL-102 exhibits a hydrogen storage capacity of approximately 1.0 wt % at 77 K when loaded at 3.5 MPa (35 bar). The hydrogen uptake is discussed in relation with the structural characteristics and the molecular simulation results. The adsorption behavior of MIL-102 at 304 K resembles that of small-pore zeolites, such as silicalite. Indeed, the isotherms of CO2, CH4, and N2 show a maximum uptake at 0.5 MPa, with no further significant adsorption up to 3 MPa. Crystal data for MIL-102: hexagonal space group P(-)6 (No. 169), a = 12.632(1) A, c = 9.622(1) A.
Grand canonical Monte Carlo (GCMC) and dual-control-volume grand canonical molecular dynamics (DC... more Grand canonical Monte Carlo (GCMC) and dual-control-volume grand canonical molecular dynamics (DCV-GCMD) simulations were carried out with Lennard-Jones model fluids in carbon nanotubes, with the objective of investigating the effect of varying molecular properties on adsorption and diffusion. The influence of the molecular weight, and the Lennard Jones parameters σ (a measure of the molecule size) and ɛ (a measure of the interaction strength) on adsorption isotherms, fluxes, and transport diffusivities was studied. For these simulations, the properties of component 1 in the mixture were held constant and one of the properties of component 2 was changed systematically. Furthermore, the validity of Graham's law, which relates the fluxes of two counter diffusing species to their molecular weight, was investigated on a molecular level. Graham's law is fulfilled for the whole range of molecular weights and Lennard-Jones parameters σ investigated. However, large deviations were observed for large values of ɛ2. Here, the interaction of the two components in the mixture becomes so strong that component 1 is dragged along by component 2.
Clusters produced in simulations of MOF assembly at metal : ligand ratios of (a) 5 : 1 and (b) 1 ... more Clusters produced in simulations of MOF assembly at metal : ligand ratios of (a) 5 : 1 and (b) 1 : 1 with identical interaction potentials.
The paper describes the first sequence of the Skarstrom cycle for bed 1 to analyze the breackthro... more The paper describes the first sequence of the Skarstrom cycle for bed 1 to analyze the breackthrough curves and studies the importance of mass transfer resistance for the performance of the PSA process which separates a feed stream consisting of equimolar fractions of methane and ethane. The diffusivities and adsorption isotherms are calculated by molecular simulation approaches.
Cancer remains hard to treat, partially due to the non-specificity of chemotherapeutics. Metal–or... more Cancer remains hard to treat, partially due to the non-specificity of chemotherapeutics. Metal–organic frameworks (MOFs) are promising carriers for targeted chemotherapy, yet, to date, there have been few detailed studies to systematically enhance drug loading while maintaining controlled release. In this work, we investigate which molecular simulation methods best capture the experimental uptake and release of cisplatin from UiO-66 and UiO-66(NH2). We then screen a series of biocompatible, pH-sensitive zeolitic imidazolate frameworks (ZIFs) for their ability to retain cisplatin in healthy parts of the patient and release it in the vicinity of a tumor. Pure-component GCMC simulations show that the maximum cisplatin loading depends on the pore volume. To achieve this maximum loading in the presence of water, either the pore size needs to be large enough to occupy both cisplatin and its solvation shell or the MOF–cisplatin interaction must be more favorable than the cisplatin–shell in...
Zinc(ii) and zirconium(iv) MOFs show uptake and slow release of the ant alarm pheromones 3-octano... more Zinc(ii) and zirconium(iv) MOFs show uptake and slow release of the ant alarm pheromones 3-octanone and 4-methyl-3-heptanone.
... Jennifer J. Williams ... Diamine-grafted SBA-15 was reported to show an enhanced adsorption c... more ... Jennifer J. Williams ... Diamine-grafted SBA-15 was reported to show an enhanced adsorption capacity of 44 mg/g.(27) Harlick et al.(28, 29) and Serna-Guerrero et al.(30) grafted 3-[2-(2-aminoethylamino)ethylamino]propyl trimethoxysilane onto MCM-41 and pore-expanded ...
A wide variety of new nanoporous metal-organic materials are being synthesized by many research g... more A wide variety of new nanoporous metal-organic materials are being synthesized by many research groups using supramolecular chemistry and directed assembly in a building block approach based on corner units and linker molecules. These materials may lead to ...
The isosteric enthalpy of adsorption for neopentane at relative pressures down to 3 × 10(-8) in M... more The isosteric enthalpy of adsorption for neopentane at relative pressures down to 3 × 10(-8) in MCM-41 was predicted for the temperature range from -15 to 0 °C. At such low pressures and temperatures, experimental measurements become problematic for this system. We used an atomistic model for MCM-41 obtained by means of a kinetic Monte Carlo method mimicking the synthesis of the material. The model was parametrized to represent experimental nitrogen adsorption isotherms at 77 K using grand canonical Monte Carlo simulations. The simulated isosteric enthalpy of adsorption shows very good agreement with available experimental data, demonstrating that GCMC simulations can predict heats of adsorption for conditions that are challenging for experimental measurements. Additional insights into the adsorption mechanisms, derived from energetic analysis at the molecular level, are also presented.
Grand canonical Monte Carlo simulations were performed to predict adsorption isotherms for hydrog... more Grand canonical Monte Carlo simulations were performed to predict adsorption isotherms for hydrogen in a series of 10 isoreticular metal-organic frameworks (IRMOFs). The results show acceptable agreement with the limited experimental results from the literature. The effects of surface area, free volume, and heat of adsorption on hydrogen uptake were investigated by performing simulations over a wide range of pressures on this set of materials, which all have the same framework topology and surface chemistry but varying pore sizes. The results reveal the existence of three adsorption regimes: at low pressure (loading), hydrogen uptake correlates with the heat of adsorption; at intermediate pressure, uptake correlates with the surface area; and at the highest pressures, uptake correlates with the free volume. The accessible surface area and free volume, calculated from the crystal structures, were also used to estimate the potential of these materials to meet gravimetric and volumetric targets for hydrogen storage in IRMOFs.
... Studies in Surface Science and Catalysis 160 PL Llewellyn, F. Rodriquez-Reinoso, J. Rouqerol ... more ... Studies in Surface Science and Catalysis 160 PL Llewellyn, F. Rodriquez-Reinoso, J. Rouqerol and N. Seaton (Editors) .9 ... King's Buildings, Edinburgh, EH9 3JL, UK b Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston ...
ABSTRACT Two Co2+ metal-organic framework materials, constructed from a combination of 1,4-benzen... more ABSTRACT Two Co2+ metal-organic framework materials, constructed from a combination of 1,4-benzenedicarboxylate (BDC) and either 2,2′-dipyridyl-N-oxide (DPNO) or 2,2′-dipyridyl-N,N′-dioxide (DPNDO), are synthesized under solvothermal reaction conditions, and their structures solved by single crystal X-ray diffraction. Both have three-dimensional structures that contain octahedral Co2+ centers with μ2-(η2)-BDC, and bidentate DPNO or DPNDO coligands that bridge pairs of metal centers but do not contribute toward the overall connectivity of the framework. Co3(BDC)3(DPNO)2 contains trimers of trans corner-shared Co-centered octahedra with one type of bridging BDC ligand forming terminal edges of the trimers, bridging to neighboring trimer units, and a second type, bridging pairs of metals and also connecting neighboring trimers. Co2(BDC)2(DPNDO) is constructed from one-dimensional inorganic chains consisting of cis- and trans-corner shared Co2+-centered octahedra. The DPNDO ligand is bis-bidentate, forming the edges of one type of octahedron and the trans corners of the second type, with the coordination for both octahedra completed by bridging BDC linkers, which in turn connect the inorganic chains to yield a three-dimensional structure. Thermogravimetric analysis shows both materials contain trapped solvent, and while Co3(BDC)3(DPNO)2 is unstable with respect to solvent loss, Co2(BDC)2(DPNDO), and its magnesium analogue, can be desolvated to yield permanently porous materials that show thermal stability up to 300 °C. For Co2(BDC)2(DPNDO), gas adsorption studies show permanent microporosity with moderate uptake of small gas molecules (N2, CO2, CH4, and C2H6), supported by Grand Canonical Monte Carlo calculations based on the assumption of rigid crystal structures, while gravimetric analysis shows rapid and reversible methanol adsorption at ambient pressure for both the Co and Mg analogues of the framework.
Journal of the American Chemical Society, Nov 22, 2006
A new three-dimensional chromium(III) naphthalene tetracarboxylate, CrIII3O(H2O)2F{C10H4(CO2)4}1.... more A new three-dimensional chromium(III) naphthalene tetracarboxylate, CrIII3O(H2O)2F{C10H4(CO2)4}1.5.6H2O (MIL-102), has been synthesized under hydrothermal conditions from an aqueous mixture of Cr(NO3)3.9H2O, naphthalene-1,4,5,8-tetracarboxylic acid, and HF. Its structure, solved ab initio from X-ray powder diffraction data, is built up from the connection of trimers of trivalent chromium octahedra and tetracarboxylate moieties. This creates a three-dimensional structure with an array of small one-dimensional channels filled with free water molecules, which interact through hydrogen bonds with terminal water molecules and oxygen atoms from the carboxylates. Thermogravimetric analysis and X-ray thermodiffractometry indicate that MIL-102 is stable up to approximately 300 degrees C and shows zeolitic behavior. Due to topological frustration effects, MIL-102 remains paramagnetic down to 5 K. Finally, MIL-102 exhibits a hydrogen storage capacity of approximately 1.0 wt % at 77 K when loaded at 3.5 MPa (35 bar). The hydrogen uptake is discussed in relation with the structural characteristics and the molecular simulation results. The adsorption behavior of MIL-102 at 304 K resembles that of small-pore zeolites, such as silicalite. Indeed, the isotherms of CO2, CH4, and N2 show a maximum uptake at 0.5 MPa, with no further significant adsorption up to 3 MPa. Crystal data for MIL-102: hexagonal space group P(-)6 (No. 169), a = 12.632(1) A, c = 9.622(1) A.
Grand canonical Monte Carlo (GCMC) and dual-control-volume grand canonical molecular dynamics (DC... more Grand canonical Monte Carlo (GCMC) and dual-control-volume grand canonical molecular dynamics (DCV-GCMD) simulations were carried out with Lennard-Jones model fluids in carbon nanotubes, with the objective of investigating the effect of varying molecular properties on adsorption and diffusion. The influence of the molecular weight, and the Lennard Jones parameters σ (a measure of the molecule size) and ɛ (a measure of the interaction strength) on adsorption isotherms, fluxes, and transport diffusivities was studied. For these simulations, the properties of component 1 in the mixture were held constant and one of the properties of component 2 was changed systematically. Furthermore, the validity of Graham's law, which relates the fluxes of two counter diffusing species to their molecular weight, was investigated on a molecular level. Graham's law is fulfilled for the whole range of molecular weights and Lennard-Jones parameters σ investigated. However, large deviations were observed for large values of ɛ2. Here, the interaction of the two components in the mixture becomes so strong that component 1 is dragged along by component 2.
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