Pulse gas chromatographic study of adsorption of substituted aromatics and heterocyclic molecules on MIL-47 at zero coverage

Big-Data Science in Porous Materials: Materials Genomics and Machine Learning

By combining metal nodes with organic linkers we can potentially synthesize millions of possible metal-organic frameworks (MOFs). The fact that we have so many materials opens many exciting avenues but also create new challenges. We simply have too many materials to be processed using conventional, brute force, methods. In this review, we show that having so many materials allows us to use big-data methods as a powerful technique to study these materials and to discover complex correlations. The first part of the review gives an introduction to the principles of big-data science. We show how to select appropriate training sets, survey approaches that are used to represent these materials in feature space, and review different learning architectures, as well as evaluation and interpretation strategies. In the second part, we review how the different approaches of machine learning have been applied to porous materials. In particular, we discuss applications in the field of gas storage and separation, the stability of these materials, their electronic properties, and their synthesis. Given the increasing interest of the scientific community in machine learning, we expect this list to rapidly expand in the coming years.

Metal-Organic Framework Materials for the Separation and Purification of Light Hydrocarbons

The separation and purification of light hydrocarbons (LHs) mixtures is one of the most significantly important but energy demanding processes in the petrochemical industry. As an alternative technology to energy intensive traditional separation methods, such as distillation, absorption, extraction, etc., adsorptive separation using selective solid adsorbents could potentially not only lower energy cost but also offer higher efficiency. The need to develop solid materials for the efficiently selective adsorption of LHs molecules, under mild conditions, is therefore of paramount importance and urgency. Metal-organic frameworks (MOFs), emerging as a relatively new class of porous organic-inorganic hybrid materials, have shown promise for addressing this challenging task due to their unparalleled features. Herein, recent advances of using MOFs as separating agents for the separation and purification of LHs, including the purification of CH₄ , and the separations of alkynes/alkenes, alkanes/alkenes, C₅ -C₆ -C₇ normal/isoalkanes, and C₈ alkylaromatics, are summarized. The relationships among the structural and compositional features of the newly synthesized MOF materials and their separation properties and mechanisms are highlighted. Finally, the existing challenges and possible research directions related to the further exploration of porous MOFs in this very active field are also discussed.

Shape selective properties of the Al-fumarate metal–organic framework in the adsorption and separation of n-alkanes, iso-alkanes, cyclo-alkanes and aromatic hydrocarbons

Adsorption properties of a wide range of hydrocarbon adsorbates in the Al-fumarate metal–organic framework are reported. Trends in adsorption behaviour are related to the sorbate's molecular properties and as well as the properties of this MOF.

Adsorption and Separation of Small Hydrocarbons on the Flexible, Vanadium-Containing MOF, COMOC-2

COMOC-2, a flexible vanadium-containing metal-organic framework, was investigated for its adsorption and separation properties of light hydrocarbons. COMOC-2 is an extended version of the MIL-47 framework with 4,4'-biphenyldicarboxylic acid linkers instead of terephthalic acid. Adsorption isotherms of methane to propane, ethylene, and propylene were determined with a gravimetric uptake technique at temperatures between 281 and 303 K. A pronounced breathing effect was observed (in contrast to the more rigid MIL-47 framework) in which the adsorption capacity increases by more than a factor of 2 at a given breathing pressure. The breathing pressure decreases with increasing hydrocarbon molecular weight. The typical two-step isotherms are nearly identical for alkanes and alkenes, in accordance with the nonpolar nature of the material. Binary isotherms of ethane and propane were also measured with the gravimetric uptake technique at different temperatures and total pressures. The mixture isotherms and breathing transition pressures were predicted by relying on the osmotic framework adsorbed solution theory (OFAST). Finally, the separation potential of COMOC-2 for ethane/propane mixtures was looked into using breakthrough experiments for different compositions and different pressures.

A pulse chemisorption/reaction system for in situ and time-resolved DRIFTS studies of catalytic reactions on solid surfaces

A pulse chemisorption/reaction system in combination with Fourier transform infrared spectrometer equipped with a diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS) reaction cell and online mass spectrometer is described in detail. Such a system provides an approach to effectively suppress the interference of the gas-phase reactants to the vibrational signals of surface adsorbates during the operando DRIFTS measurements and, thus, allows for in situ and real-time monitor of surface species on catalyst surfaces during chemisorption/reaction processes. Employing this system, we successfully acquired DRIFTS spectra that clearly demonstrate surface species formed by propylene chemisorption and reaction on octahedral Cu2O nanocrystals; we also observed simultaneous chemisorption of CO on top, twofold, and threefold bridged sites of Pd nanoparticles supported on SiO2 upon the collision of CO prior to the saturation of strongly bound sites and the transformation of weakly bound CO(a) into strongly bound CO(a) during the dynamic chemisorption-desorption processes.