The application of machine learning for predicting the methane uptake and working capacity of MOFs

Multiple linear regression analysis, as a part of machine learning, is employed to develop equations for the quick and accurate prediction of the methane uptake and working capacity of metal–organic frameworks (MOFs). Only three crystal characteristics of MOFs (geometric descriptors) are employed for developing the equations: surface area, pore volume and density of the crystal structure. The values of the geometric descriptors can be obtained much more cheaply in terms of time and other resources compared to running calculations of gas sorption or performing experimental work. Within this work sets of equations are provided for the different cases studied: a series of MOFs with NbO topology, a set of benchmark MOFs with outstanding methane storage and working capacities, and the whole CoRE MOF database (11 000 structures)

A novel bismuth-based metal-organic framework for high volumetric methane and carbon dioxide adsorption

Solvothermal reaction of H4L (L = biphenyl-3,3’,5,5’-tetracarboxylate) and Bi(NO3)3·(H2O)5 in a mixture of DMF/MeCN/H2O in the presence of piperazine and nitric acid at 100 oC for 10 h affords the solvated metal-organic polymer [Bi2(L)1.5(H2O)2]·(DMF)3.5·(H2O)3 (NOTT-220-solv). A single crystal X-ray structure determination confirms that it crystallises in space group P2/c and has a neutral and non-interpenetrated structure comprising binuclear {Bi2} centres bridged by tetracarboxylate ligands. NOTT-220-solv shows a 3,6-connected network having a new framework topology with a {4·62}2{42·65·88}{62·8} point symbol. The desolvated material NOTT-220a shows exceptionally high adsorption uptakes for CH4 and CO2 on a volumetric basis at moderate pressures and temperatures with a CO2 uptake of 553 gL-1 (20 bar, 293 K) with a saturation uptake of 688 gL-1 (1 bar, 195 K). The corresponding CH4 uptake of 165 V(STP)/V (20 bar, 293 K) and 189 V(STP/V) (35 bar, 293 K) is within the top three MOF materials under the same conditions, surpassed only by PCN-14 and Ni-MOF-74 (230 and 190 V(STP)/V 35 Bar, 298 K). The maximum CH4 uptake for NOTT-220a was recorded at 20 bar and 195 K to be 287 V(STP)/V, while H2 uptake of NOTT-220a at 20 bar, 77 K is 42 gL-1. These gas uptakes have been modelled by Grand Canonical Monte Carlo (GCMC) and Density Functional Theory (DFT) calculations, which confirm the experimental data and give insights into the nature of the binding sites of CH4 and CO2 in this porous hybrid material

Differential guest location by host dynamics enhances propylene/propane separation in a metal-organic framework

Energy-efficient approaches to propylene/propane separation such as molecular sieving are of considerable importance for the petrochemical industry. The metal organic framework NbOFFIVE-1-Ni adsorbs propylene but not propane at room temperature and atmospheric pressure, whereas the isostructural SIFSIX-3-Ni does not exclude propane under the same conditions. The static dimensions of the pore openings of both materials are too small to admit either guest, signalling the importance of host dynamics for guest entrance to and transport through the channels. We use ab initio calculations together with crystallographic and adsorption data to show that the dynamics of the two framework-forming units, polyatomic anions and pyrazines, govern both diffusion and separation. The guest diffusion occurs by opening of the flexible window formed by four pyrazines. In NbOFFIVE-1-Ni, (NbOF5)2- anion reorientation locates propane away from the window, which enhances propylene/propane separation

Observation of Binding and Rotation of Methane and Hydrogen within a Functional Metal-Organic Framework

The key requirement for a portable store of natural gas is to maximize the amount of gas within the smallest possible space. The packing of methane (CH₄) in a given storage medium at the highest possible density is, therefore, a highly desirable but challenging target. We report a microporous hydroxyl-decorated material, MFM-300­(In) (MFM = Manchester Framework Material, replacing the NOTT designation), which displays a high volumetric uptake of 202 v/v at 298 K and 35 bar for CH₄ and 488 v/v at 77 K and 20 bar for H₂. Direct observation and quantification of the location, binding, and rotational modes of adsorbed CH₄ and H₂ molecules within this host have been achieved, using neutron diffraction and inelastic neutron scattering experiments, coupled with density functional theory (DFT) modeling. These complementary techniques reveal a very efficient packing of H₂ and CH₄ molecules within MFM-300­(In), reminiscent of the condensed gas in pure component crystalline solids. We also report here, for the first time, the experimental observation of a direct binding interaction between adsorbed CH₄ molecules and the hydroxyl groups within the pore of a material. This is different from the arrangement found in CH₄/water clathrates, the CH₄ store of nature

Analysis of high and selective uptake of CO2 in an oxamide-containing {Cu2(OOCR)4}-based metal-organic framework

The porous framework [Cu2(H2O)2L].4H2O.2DMA ((H¬4¬L = oxalylbis(azanediyl)diisophthalic acid; DMA = N,N-dimethylacetamide), denoted NOTT-125, is formed by connection of {Cu2(RCOO)4} paddlewheels with the isophthalate linkers in L4-. A single crystal structure determination reveals that NOTT-125 crystallises in monoclinic cell with a = 27.9161(6) Å, b = 18.6627(4) Å and c = 32.3643(8) Å, space group P2 (1)/c. The structure of this material shows fof topology, which can be viewed as the packing of two types of cages (Cage A and Cage B) in 3-dimensional space. Cage A is constructed by twelve {Cu2(OOCR)4} paddlewheels and six linkers to form an ellipsoid-shaped cavity approximately 24.0 Å along its long axis and 9.6 Å across the central diameter. Cage B consists of six {Cu2(OOCR)4} units and twelve linkers with a spherical diameter of 12.7 Å taking into account the van der Waals radii of the atoms. NOTT-125 incorporates oxamide functionality within the pore walls, and this, combined with high porosity in the desolvated NOTT-125a, is responsible for excellent CO2 uptake (40.1 wt% at 273 K and 1 bar) and selectivity for CO2 over CH4 or N2. Grand canonical Monte Carlo (GCMC) simulations show excellent agreement with the experimental gas isotherm data, and a computational study into the specific interactions and binding energies of both CO2 and CH4 with the linkers in NOTT-125 reveals a set of strong interactions between CO2 and the oxamide motif, which are not possible with a single amide

Chemical reactions at the graphitic step-edge: changes in product distribution of catalytic reactions as a tool to explore the environment within carbon nanoreactors

A series of explorative cross-coupling reactions have been developed to investigate the local nanoscale environment around catalytically active Pd(II)complexes encapsulated within hollow graphitised nanofiber (GNF). Two new fullerene-containing and fullerene-free Pd(II)Salen catalysts have been synthesised, and their activity and selectivity towards different substrates has been explored in nanoreactors. The catalysts not only show a significant increase in activity and stability upon heterogenisation at the graphitic step-edges inside the GNF channel, but also exhibit a change in selectivity affected by the confinement which alters the distribution of isomeric products of the reaction. Furthermore, the observed selectivity changes reveal unprecedented details regarding the location and orientation of the catalyst molecules inside the GNF nanoreactor, inaccessible by any spectroscopic or microscopic techniques, thus shedding light on the precise reaction environment inside the molecular catalyst-GNF nanoreactor. Keywords: nanoreactor, catalysis, fullerene, salen, cross-couplin

Methane adsorption in metal-organic frameworks containing nanographene linkers: a computational study

Metal-organic framework (MOF) materials are known to be amenable to expansion through elongation of the parent organic linker. For a family of model (3,24)-connected MOFs with the rht topology, in which the central part of organic linker comprises a hexabenzocoronene unit, the effect of the linker type and length on their structural and gas adsorption properties is studied computationally. The obtained results compare favourably with known MOF materials of similar structure and topology. We find that the presence of a flat nanographene-like central core increases the geometric surface area of the frameworks, sustains additional benzene rings, promotes linker elongation and the efficient occupation of the void space by guest molecules. This provides a viable linker modification method with potential for enhancement of uptake for methane and other gas molecules

A robust binary supramolecular organic framework (SOF) with high CO2 adsorption and selectivity

A robust binary hydrogen-bonded supramolecular organic framework (SOF-7) has been synthesized by solvothermal reaction of 1,4-bis-(4-(3,5-dicyano-2,6 dipyridyl)dihydropyridyl)benzene (1) and 5,5’-bis-(azanediyl)-oxalyl-diisophthalic acid (2). Single crystal X-ray diffraction analysis shows that SOF-7 comprises 2 and 1,4-bis-(4-(3,5-dicyano-2,6-dipyridyl)pyridyl)benzene (3), the latter formed in situ from the oxidative dehydrogenation of 1. SOF-7 shows a three-dimensional four-fold interpenetrat-ed structure with complementary O−H···N hydrogen bonds to form channels that are decorated with cyano- and amide-groups. SOF-7 exhibits excellent thermal stability and sol-vent and moisture durability, as well as permanent porosity. The activated desolvated material SOF-7a shows high CO2 sorption capacity and selectivity compared with other po-rous organic materials assembled solely through hydrogen bonding

Contemporary educational techniques of studying finance and financial markets

The article is dealing with modern techniques of teaching students as well as interested parties of various courses in economic disciplines. The article covers new approaches to studying finance and financial markets. The article shows the necessity of studying finance and financial markets. The authors come up with the proposals how to improve the educational level of different categories of society. The article considers the methods of distant learning when working on the financial markets