Liquid- and Gas-Phase Diffusion of Ferrocene in Thin Films of Metal-Organic Frameworks

Zhou, Wencai; Wöll, Christof; Heinke, Lars

doi:10.3390/ma8063767

Cited by 35 publications

(25 citation statements)

References 44 publications

(49 reference statements)

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“…For example, it would take more than a year for a 50 µm MOF crystal to uptake molecules with a diffusion coefficient of 10 −18 m 2 s −1 . [31] Taking advantage of the optical transparency of high-quality SURMOFs allows the investigation of multicomponent, i.e., binary and ternary mixture, uptake of dye molecules. [27] Several previous works demonstrated that SURMOFs are ideal to serve as model systems for studying diffusion in nanoporous frameworks (Figure 4).…”

Section: Unique Model System For Diffusion Experimentsmentioning

confidence: 99%

“…[30] The rigid attachment of SURMOF samples to the solid support also permits investigations of the uptake from the liquid and gas phases by the very same sample. [31] Taking advantage of the optical transparency of high-quality SURMOFs allows the investigation of multicomponent, i.e., binary and ternary mixture, uptake of dye molecules. [32]…”

Section: Unique Model System For Diffusion Experimentsmentioning

confidence: 99%

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Surface‐Mounted Metal–Organic Frameworks: Crystalline and Porous Molecular Assemblies for Fundamental Insights and Advanced Applications

2019

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with open voids attract significant interest, not only for use in gas storage and separation applications, [1b] but also as model systems used for fundamental investigations on molecular interactions. After being introduced about two decades ago, [2] this new type of crystalline coordination network created considerable excitement and much effort was devoted toward the discovery of new types of these compounds. In early 2017, after 20 years of intense research, the literature contains reports on more than 70 000 structurally characterized examples of this class. [3] Since MOFs can be assembled by combining molecular building blocks, specifically ditopic or higher-topic organic linkers and metal or metal-oxo nodes, a virtually unlimited number of structures can be realized. Moreover, essentially every organic molecule can be modified by the addition of appropriate coupling groups, e.g., carboxylic acid groups or pyridine units, to yield a ditopic linker. Therefore, the number of possible MOF structures is far greater than the number of known structures. In line with this consideration, more than a million of these compounds have been simulated using combinatorial approaches. [4] As MOFs are both crystalline and porous, they have fascinating and often surprising properties. Not only does the immense chemical space spanned by these compounds create enormous potential for advancing materials science, it also provides ideal matrices for reference experiments exploring fundamental spectroscopic and physicochemical properties. The framework provides a well-defined, crystalline, porous environment that can host guest molecules, thus permitting systematic spectroscopic investigations. In contrast to solvents or polymer matrices, MOFs provide a strictly periodic, very well defined structural framework, where the molecular environment is identical for each embedded guest molecule. In this respect, MOFs outperform amorphous noble-gas guest matrices [5] in which the environment surrounding varies from site to site, leading to inhomogeneous broadening of the embedded guest's spectroscopic features, including vibrational bands.Herein, we discuss the use of MOFs and, in particular, of surface-mounted metal-organic frameworks (SURMOFs), to provide well-defined environments for precisely determining Metal-organic frameworks (MOFs) are crystalline coordination polymers, assembled from inorganic nodes connected by organic linker molecules. An enormous surface area, huge compositional variety, regular structure, and favorable mechanical properties are among their outstanding properties. Monolithic MOF thin films, i.e., surface-mounted metalorganic frameworks (SURMOFs), with high degree of structural order and adjustable defect density, can be prepared on solid substrates using layer-by-layer techniques. Recent studies where SURMOFs served as model systems for quantitative studies of molecular interactions in porous media, including diffusion, are reviewed. Moreover, SURMOFs are ideally suited for the incorporation of photoactive mo...

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Section: Unique Model System For Diffusion Experimentsmentioning

confidence: 99%

Section: Unique Model System For Diffusion Experimentsmentioning

confidence: 99%

Surface‐Mounted Metal–Organic Frameworks: Crystalline and Porous Molecular Assemblies for Fundamental Insights and Advanced Applications

2019

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“…By means of liquid-phase epitaxy, surface-mounted MOFs (SURMOFs) can be directly prepared on the solid substrate surface. 27,28 Two pillared-layer MOF structures based on organic linker molecules with azobenzene side groups are investigated: Cu 2 (BDC) 2 (AzoBiPyB) and Cu 2 (DMTPDC) 2 (AzoBiPyB) (AzoBiPyB: 4,4 0 -(2-(phenyldiazenyl)-1,4-phenylene)dipyridine); 29 BDC: benzene-1,4-dicarboxylic acid, DMTPDC: 2,2 00 -dimethyl-[1,1 0 :4 0 ,1 00 -terphenyl]-4,4 00 -dicarboxylic acid, see ESI † (SI1). 25 Furthermore, SURMOFs can be studied in a straightforward fashion by surface-sensitive spectroscopic techniques like X-ray photoelectron spectroscopy (XPS) 26 and infrared reflection-absorption spectroscopy (IRRAS).…”

Section: Introductionmentioning

confidence: 99%

cis-to-trans isomerization of azobenzene investigated by using thin films of metal–organic frameworks

Wang

Buchholz

et al. 2015

Phys. Chem. Chem. Phys.

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The activation barrier for cis-to-trans isomerization is a key parameter for governing the properties of photoswitchable molecules. This quantity can be computed by using theoretical methods, but experimental determination is not straightforward. Photoswitchable molecules typically do not change their conformation in the pure crystalline state. When the molecules are in solution, the switching is affected by the viscosity and polarity of the solvent and when embedded in polymers, the conformational change is affected by the polymer matrix. Here, we describe a novel approach where the photoswitchable group is integrated in a highly crystalline, porous molecular framework. Sufficiently large pore sizes in such metal-organic frameworks, MOFs, allow unhindered switching and the strictly periodic structure of the lattice eliminates virtually all contributions from inhomogeneities. Using IR spectroscopy to probe the conformational state of azobenzene, the energy barrier separating the cis and the trans state could be determined by an Arrhenius analysis of the data accumulated in a temperature regime between 314 K and 385 K. The result, 1.09 ± 0.09 eV, is in very good agreement with the activation energy reported for the thermal cis-to-trans isomerization of free azobenzene as computed by DFT calculations.

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“…By using the SURMOF approach, the film can be grown directly on the QCM sensor, allowing the direct real-time quantification of the mass during the synthesis. By connecting the QCM to a liquid-or gas-flow system, the molecular uptake by the SURMOF from the liquid or gas phase can be measured [41,42]. Taking advantage of the mass quantification by QCM, the uptake in units of guest molecules per MOF pore (or per unit cell) can be directly calculated.…”

Section: Precise Uptake Measurements Using a Quartz Crystal Microbalamentioning

confidence: 99%

Thin Films of Homochiral Metal–Organic Frameworks for Chiroptical Spectroscopy and Enantiomer Separation

Chun

Heinke

2020

Symmetry

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Chiral nanoporous solids are a fascinating class of materials, allowing efficient enantiomer separation. Here, we review the status, applications, and potential of thin films of homochiral metal–organic frameworks (MOFs). Combining the advantages of MOFs, whose well-defined, crystalline structures can be rationally tuned, with the benefits of thin films enables new opportunities for the characterization of the enantioselectivity, e.g., via chiroptical spectroscopy and straightforward molecular uptake quantifications. By incorporating photoresponsive molecules in the chiral MOF films, the enantioselectivity of the material can be dynamically remote-controlled. The most promising application of MOF films is their use as membranes, where the enantioselective separation of chiral molecules is demonstrated and parameters for further improvements are discussed.

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Liquid- and Gas-Phase Diffusion of Ferrocene in Thin Films of Metal-Organic Frameworks

Cited by 35 publications

References 44 publications

Surface‐Mounted Metal–Organic Frameworks: Crystalline and Porous Molecular Assemblies for Fundamental Insights and Advanced Applications

Surface‐Mounted Metal–Organic Frameworks: Crystalline and Porous Molecular Assemblies for Fundamental Insights and Advanced Applications

cis-to-trans isomerization of azobenzene investigated by using thin films of metal–organic frameworks

Thin Films of Homochiral Metal–Organic Frameworks for Chiroptical Spectroscopy and Enantiomer Separation

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