Metal–organic frameworks (MOFs) have become promising materials for multiple applications due to their controlled dimensionality and tunable properties. The incorporation of chirality into their ...frameworks opens new strategies for chiral separation, a key technology in the pharmaceutical industry as each enantiomer of a racemic drug must be isolated. Here, we describe the use of a combination of computational modeling and experiments to demonstrate that high-performance liquid chromatography (HPLC) columns packed with TAMOF-1 as the chiral stationary phase are efficient, versatile, robust, and reusable with a wide array of mobile phases (polar and non-polar). As proof of concept, in this article, we report the resolution with TAMOF-1 HPLC columns of nine racemic mixtures with different molecular sizes, geometries, and functional groups. Initial in silico studies allowed us to predict plausible separations in chiral compounds from different families, including terpenes, calcium channel blockers, or P-stereogenic compounds. The experimental data confirmed the validity of the models and the robust performance of TAMOF-1 columns. The added value of in silico screening is an unprecedented achievement in chiral chromatography.
The metal-organic framework MOF-808 contains Zr6O8 nodes with a high density of vacancy sites, which can incorporate carboxylate-containing functional groups to tune chemical reactivity. Although the ...postsynthetic methods to modify the chemistry of the Zr6O8 nodes in MOFs are well known, tackling these alterations from a structural perspective is still a challenge. We have combined infrared spectroscopy experiments and first-principles calculations to identify the presence of node vacancies accessible for chemical modifications within the MOF-808. We demonstrate the potential of our approach to assess the decoration of MOF-808 nodes with different catechol–benzoate ligands. Furthermore, we have applied advanced synchrotron characterization tools, such as pair distribution function analyses and X-ray absorption spectroscopy, to resolve the atomic structure of single metal sites incorporated into the catechol groups postsynthetically. Finally, we demonstrate the catalytic activity of these MOF-808 materials decorated with single copper sites for 1,3-dipolar cycloadditions.
Adsorption of polar and nonpolar molecules in hydrophilic–hydrophobic STAM-1 metal–organic framework was studied by means of quasi-equilibrated temperature-programmed desorption and adsorption ...(QE-TPDA) experimental technique and molecular simulation. The QE-TPDA measurements revealed that thermal stability of the studied material in the presence of water may be lower than determined from thermogravimetric analysis. Molecular dynamics showed evident impact of diffusion on the adsorption mechanism in STAM-1. The QE-TPDA profiles recorded for adsorption of n-alkanes, water, and alcohols indicate the gate-opening effect occurring only upon adsorption of polar molecules, which was confirmed by in situ IR spectroscopy. Monte Carlo molecular simulations agree with experimental data revealing preferable adsorption sites for the molecules of alcohols in STAM-1. Simulations also showed that the molecular mechanism of the gate-opening is dependent on the size of polar guest molecules.
Adsorption of n-alkanes from pentane to decane (C5–C10) in zeolites LTA (ITQ-29 and 5A) and faujasite (FAU, dealuminated high-silica Na-FAU, NaY, and NaX) as well as branched hexane isomers in FAU ...was investigated by means of experimental quasi-equilibrated temperature-programmed desorption and adsorption (QE-TPDA) and theoretical Monte Carlo molecular simulations. A novel QE-TPDA method of studying porosity provided high-quality desorption–adsorption profiles and adsorption isobars of hydrocarbons. A unique two-step adsorption of long-chain alkanes in LTA zeolites was observed and explained in detail based on the results of the theoretical calculations. Although adsorption of n-alkanes in FAU is a one-step process, it also does not occur in a uniform manner because of strong lateral interactions at high loadings. We also investigated the influence of cation content on adsorption equilibrium and energetics for the studied adsorbent–adsorbate systems, finding a nonlinear relation between heat of adsorption and content of cations in FAU. Investigations on packing of the molecules of n-alkanes were also performed, revealing relations between chain length of the probe molecule and sorption capacity of the studied materials.
Thermal energy storage using porous materials has become a key technology for improving efficiency and sustainability of heat storage applications to reduce the carbon dioxide emissions. Choosing the ...adsorbent–fluid working pairs that improve the performance of an energy storage process is a challenge due to the large number of possible combinations. The use of activated carbons for adsorption, purification, and energy applications as an alternative to other porous materials such as zeolites or silica gel is a promising strategy due to its low production cost combined to a good thermochemical energy storage performance. In this work, we have explored the use of activated carbons derived from the pyrolysis of saccharose coke (CS1000a) for thermal energy storage. For this, we have considered the first four n-alcohols (methanol, ethanol, 1-propanol, and 1-butanol) as working fluids because of their large enthalpy of vaporization. We carried out Monte Carlo simulations combined with the thermodynamical model based on the Dubinin-Polanyi theory to evaluate adsorption, interaction energies, microscopic structure, and thermal energy storage density of CS1000a–alcohol pairs. We compared these properties with the performance of other commercial activated carbon, such as BPL. We employed a realistic model containing functional groups in the internal surface and a simplified model without these functional groups. The role of these functional groups and their consequences on the targeted properties is discussed. CS1000a shows excellent performance to store thermal energy and considerably reduces the operational temperatures, making it a good alternative to those on the market.
Separation of Volatile Organic Compounds in TAMOF‑1 González-Galán, Carmen; de Fez-Febré, Mabel; Giancola, Stefano ...
ACS applied materials & interfaces,
07/2022, Letnik:
14, Številka:
27
Journal Article
Recenzirano
Odprti dostop
Separation of volatile organic compounds is one of the most studied processes in industry. TAMOF-1 is a homochiral metal–organic framework with a crystalline network of interconnected ≈1 nm channels ...and has high thermal and chemical stability. Thanks to these features, it can resolve racemic mixtures of chiral drugs as a chiral stationary phase in chromatography. Interestingly, the particular shape and size of its channels, along with the presence of metallic centers and functional groups, allow establishing weak but significant interactions with guest molecules. This opens interesting possibilities not only to resolve racemates but also to separate other organic mixtures, such as saturated/unsaturated and/or linear/branched molecules. In search of these applications, we have studied the separation of volatile organic compounds in TAMOF-1. Monte Carlo simulations in the grand-canonical ensemble have been carried out to evaluate the separation of the selected molecules. Our results predict that TAMOF-1 is able to separate xylene isomers, hexane isomers, and benzene–cyclohexane mixtures. Experimental breakthrough analysis in the gas phase and also in the liquid phase confirms these predictions. Beds of TAMOF-1 are able to recognize the substitution in xylenes and the branching in hexanes, yielding excellent separation and reproducibility, thanks to the chemical and mechanical features of this material.
We have developed a complete force field that accurately reproduces the adsorption properties of carbon dioxide in a variety of zeolites with different topologies and compositions. The force field ...parameters were obtained by fitting to our own experimental data and validated with available data taken from the literature. The novelty of this force field is that it is fully transferable between different zeolite framework types, and therefore, it is applicable to all possible Si/Al ratios (with sodium as extra-framework cation) and for the first time affording the prediction of topology-specific and chemical composition-specific adsorption properties.
The adsorption of several quadrupolar and nonpolar gases on the Metal Organic Framework Cu-BTC has been studied by combining experimental measurements and Monte Carlo simulations. Four main ...adsorption sites for this structure have been identified: site I close to the copper atoms, site I′ in the bigger cavities, site II located in the small octahedral cages, and site III at the windows of the four open faces of the octahedral cage. Our simulations identify the octahedral cages (sites II and III) and the big cages (site I′) as the preferred positions for adsorption, while site I, near the copper atoms, remains empty over the entire range of pressures analyzed due to its reduced accessibility. The occupation of the different sites for ethane and propane in Cu-BTC proceeds similarly as for methane, and shows small differences for O2 and N2 that can be attributed to the quadrupole moment of these molecules. Site II is filled predominantly for methane (the nonpolar molecule), whereas for N2, the occupation of II and I′ can be considered almost equivalent. The molecular sitting for O2 shows an intermediate behavior between those observed for methane and for N2. The differences between simulated and experimental data at elevated temperatures for propane are tentatively attributed to a reversible change in the lattice parameters of Cu-BTC by dehydration and by temperature, blocking the accessibility to site III and reducing that to site I′. Adsorption parameters of the investigated molecules have been determined from the simulations.
Adsorption of n-alkanes from methane to decane (C1–C10) on AlPO4-5 aluminophosphate was studied by means of Monte Carlo simulations. The additional experimental study with use of quasi-equilibrated ...temperature-programmed desorption and adsorption (QE-TPDA) yielded high quality adsorption isobars of C5–C10 n-alkanes. The QE-TPDA based isotherms were accurately reproduced in the simulation, thus validating the applied force field. The agreement between experimental and simulated data indicated that the QE-TPDA is a reliable method for studying porosity-related adsorptive properties. The simulations revealed differences in the adsorption mechanism of the n-alkane series, with unmistakable site-based adsorption for short molecules (C1–C5) at saturation. Kinetic properties of the studied systems determined with the use of molecular dynamics exposed chain length dependency of the self-diffusion coefficient, indicating probably a resonant diffusion mechanism.
We use molecular simulation to study the selective adsorption of BTEX mixtures (benzene, toluene, ethylbenzene, xylenes) in metal–organic frameworks. The adsorption of these compounds is a basic step ...in reutilizing petrochemical industry derivatives. BTEX mixture components are precursors to polymers such as poly(ethylene terephthalate). It is also important to store these molecules due to their high toxicity to humans. We study the storage, adsorption selectivity, distribution, and overall behavior of the adsorbed molecules inside the structures. We use MOF-1, MIL-47, and IRMOF-1 to test the effect of the size of the cavities and the topology of the structure in the adsorption of the components of the mixture. We found that these structures are useful to separate ethylbenzene and o-xylene from the BTEX mixtures.
