Acidic and basic sites of M2DEBDC (M = Mg or Mn and E = O or S) acting as catalysts for cyanosilylation of aldehydes

Experimental and theoretical structural investigation of an ionic Nd coordination polymer

Research concerning coordination polymers has been intense due to their significant variability and structural stability. With this in mind, an ionic neodymium coordination polymer was synthesized, composed of an anionic one-dimensional polymer interconnected to a cationic three-dimensional porous polymer, poly[dodecaaquabis(μ-pyridine-4-carbohydrazide-κ2N:O)bis(μ2-4-sulfobenzoato-κ2O:O')bis(μ3-4-sulfobenzoato-κ3O:O':O'')trineodymium(III)] catena-poly[aquabis(μ-pyridine-4-carbohydrazide-κ2N:O)bis(μ2-4-sulfobenzoato-κ2O:O')neodymium(III)] 4.33-hydrate, {[Nd3(C7H4O5S)4(C6H7N3O)2(H2O)12][Nd(C7H4O5S)2(C6H7N3O)2(H2O)]·4.33H2O}n. The ligands used were 4-sulfobenzoate (PSB) and pyridine-4-carbohydrazide, popularly known as isoniazid (INH), an antibiotic drug. The compound crystallizes in the monoclinic space group C2/c, with Z = 4. Solid-state calculations suggest that the crystal structure is mainly stabilized by hydrogen bonds, i.e. O-H...O and N-H...O interactions among the polymers, and by van der Waals interactions involving the organic side chains. This net is tetragonal, 2-nodal 3,4-connected, and can be described as the dmd (sqc 528) type.

Electronic Structure Modeling of Metal-Organic Frameworks

Owing to their molecular building blocks, yet highly crystalline nature, metal-organic frameworks (MOFs) sit at the interface between molecule and material. Their diverse structures and compositions enable them to be useful materials as catalysts in heterogeneous reactions, electrical conductors in energy storage and transfer applications, chromophores in photoenabled chemical transformations, and beyond. In all cases, density functional theory (DFT) and higher-level methods for electronic structure determination provide valuable quantitative information about the electronic properties that underpin the functions of these frameworks. However, there are only two general modeling approaches in conventional electronic structure software packages: those that treat materials as extended, periodic solids, and those that treat materials as discrete molecules. Each approach has features and benefits; both have been widely employed to understand the emergent chemistry that arises from the formation of the metal-organic interface. This Review canvases these approaches to date, with emphasis placed on the application of electronic structure theory to explore reactivity and electron transfer using periodic, molecular, and embedded models. This includes (i) computational chemistry considerations such as how functional, k-grid, and other model variables are selected to enable insights into MOF properties, (ii) extended solid models that treat MOFs as materials rather than molecules, (iii) the mechanics of cluster extraction and subsequent chemistry enabled by these molecular models, (iv) catalytic studies using both solids and clusters thereof, and (v) embedded, mixed-method approaches, which simulate a fraction of the material using one level of theory and the remainder of the material using another dissimilar theoretical implementation.

Investigating greenhouse gas adsorption in MOFs SIFSIX-2-Cu, SIFSIX-2-Cu-i, and SIFSIX-3-Cu through computational studies

The selective adsorption of CO₂ in mixture with other greenhouse gases by porous materials is challenging and it has several consequences from the environmental and economic point of view. We carried out DFT calculations with periodic boundary conditions and plane waves basis set to better understand the adsorption of CO₂, CO, CH₄, N₂, O₂, and H₂ within the pore of the metal-organic frameworks (MOFs) SIFSIX-2-Cu, SIFSIX-2-Cu-i, and SIFSIX-3-Cu. These porous materials have a copper ion coordinated to an organic linker and the inorganic SiF₆^2- pillar, and they show a remarkable CO₂ uptake. Our results show that the adsorption occurs preferentially close to the inorganic pillar SiF₆, which polarizes the gas molecule, increasing the electrostatic contribution to the interaction. The adsorption strength correlates with the size of the pore, and it is stronger in the smaller porous of SIFSIX-3-Cu for all gases. The successive loading of CO₂ in a T-shape form inside the porous indicates a synergic polarization effect, increasing the adsorption energy in SIFSIX-2-Cu and SIFSIX-2-Cu-i, but not in SIFSIX-3-Cu. For all materials, we observe the following order in the adsorption energy: CO₂ > CH₄ > CO > N₂ > O₂ > H₂, suggesting that a thermodynamic separation could be possible; however, kinetic effects are also important in SIFSIX-3-Cu. Graphical abstract.