Functional materials discovery using energy–structure–function maps

Molecular crystals cannot be designed in the same manner as macroscopic objects, because they do not assemble according to simple, intuitive rules. Their structures result from the balance of many weak interactions, rather than from the strong and predictable bonding patterns found in metal–organic frameworks and covalent organic frameworks. Hence, design strategies that assume a topology or other structural blueprint will often fail. Here we combine computational crystal structure prediction and property prediction to build energy–structure–function maps that describe the possible structures and properties that are available to a candidate molecule. Using these maps, we identify a highly porous solid, which has the lowest density reported for a molecular crystal so far. Both the structure of the crystal and its physical properties, such as methane storage capacity and guest-molecule selectivity, are predicted using the molecular structure as the only input. More generally, energy–structure–function maps could be used to guide the experimental discovery of materials with any target function that can be calculated from predicted crystal structures, such as electronic structure or mechanical properties

Zeolitic imidazole frameworks: structural and energetics trends compared with their zeolite analogues

International audienceWe use periodic DFT calculations to compute the total energy of known zeolitic imidazole frameworks (ZIFs) together with those of hypothetical porous ZIFs. We show that the total energy of ZIFs decreases with increasing density, in a similar fashion to the alumino-silicate zeolites, but with a more complex energy landscape. The computational evaluation of the stability of hypothetical ZIFs is useful in the search for viable synthesis targets. Our results suggest that a number of hitherto undiscovered nanoporous topologies should be amenable to synthesis (CAN, ATN) and that even the most open framework types might be obtained with appropriately substituted ligands

Polyoxometalates Functionalized by Bisphosphonate Ligands: Synthesis, Structural, Magnetic, and Spectroscopic Characterizations and Activity on Tumor Cell Lines

International audienc

epsilon-Keggin-based coordination networks: Synthesis, structure and application toward green synthesis of polyoxometalate@graphene hybrids

Four coordination networks based on the {epsilon-(PMo8Mo4O40)-Mo-V-O-VI(OH)(4)Zn-4} Keggin unit (epsilon Zn) have been synthesized under hydrothermal conditions. (TBA)(3){(PMo8Mo4O36)-Mo-V-O-VI(OH)(4)Zn-4}[C6H4(COO)(2)](2) (epsilon(isop)(2)) is a 2D material with monomeric eZn units connected via 1,3 benzenedicarboxylate (isop) linkers and tetrabutylammonium (TBA) counter-cations lying between the planes. In (TPA)(3){(PMo8Mo4O37)-Mo-V-O-VI(OH)(3)Zn-4}[C6H3(COO)(3)] (TPA[epsilon(trim)]infinity), 1D inorganic chains formed by the connection of epsilon Zn POMs, via Zn-O bonds, are linked via 1,3,5 benzenetricarboxylate (trim) ligands into a 2D compound with tetrapropylammonium (TPA) cations as counter-cations. (TBA) {(PMo8Mo4O40Zn4)-Mo-V-O-VI}(C7H4N2)(2)(C7H5N2)(2)center dot 12H(2)O (epsilon(bim)(4)) is a molecular material with monomeric epsilon Zn POMs bound to terminal benzimidazole (bim) ligands. Finally, (TBA)(C10H10N4)(2)(HPO3) {PMo(8)(V)Mo(4)(VI)O(4)0Zn(4)}(2)(C10H9N4)(3)(C10H8N4) (epsilon(2)(pazo)(4)) is a 1D compound with dimeric (epsilon Zn)(2) POMs connected by HPO32- ions and terminal para-azobipyridine (pazo) ligands. In this compound an unusual bond cleavage of the central N=N bond of the pazo ligand is observed. We report also a green chemistry-type one-step synthesis method carried out in water at room temperature using epsilon(2)(pazo)(4) and epsilon(isop)(2) as reducing agent of graphite oxide (GO) to obtain graphene (G). The POM@G hybrids were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, powder X-ray diffraction, energy dispersive X-ray analysis, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and cyclic voltammetry

1D-2D-3D Transformation Synthesis of Hierarchical Metal-Organic Framework Adsorbent for Multicomponent Alkane Separation

A new hierarchical MOF consisting of Cu(II) centers connected by benzene-tricarboxylates (BTC) is prepared by thermoinduced solid transformation of a dense CuBTC precursor phase. The mechanism of the material formation has been thoroughly elucidated and revealed a transformation of a ribbon-like 1D building unit into 2D layers and finally a 3D network. The new phase contains excess copper, charge compensated by systematic hydroxyl groups, which leads to an open microporous framework with tunable permanent mesoporosity. The new phase is particularly attractive for molecular separation. Energy consumption of adsorptive separation processes can be lowered by using adsorbents that discriminate molecules based on adsorption entropy rather than enthalpy differences. In separation of a 11-component mixture of C1-C6 alkanes, the hierarchical phase outperforms the structurally related microporous HKUST-1 as well as silicate-based hierarchical materials. Grand canonical Monte Carlo (GCMC) simulation provides microscopic insight into the structural host-guest interaction, confirming low adsorption enthalpies and significant entropic contributions to the molecular separation. The unique three-dimensional hierarchical structure as well as the systematic presence of Cu(II) unsaturated coordination sites cause this exceptional behavior.status: publishe

Polyoxometalates Functionalized by Bisphosphonate Ligands: Synthesis, Structural, Magnetic, and Spectroscopic Characterizations and Activity on Tumor Cell Lines

We report the synthesis and characterization of eight new Mo, W, or V-containing polyoxometalate (POM) bisphosphonate complexes with metal nuclearities ranging from 1 to 6. The compounds were synthesized in water by treating Mo^VI, W^VI, V^IV, or V^V precursors with biologically active bisphosphonates H₂O₃PC(R)­(OH)­PO₃H₂ (R = C₃H₆NH₂, Ale; R = CH₂S­(CH₃)₂, Sul and R = C₄H₅N₂, Zol, where Ale = alendronate, Sul = (2-Hydroxy-2,2-bis-phosphono-ethyl)-dimethyl-sulfonium and Zol = zoledronate). <b>Mo</b>_<b>6</b><b>(Sul)</b>_<b>2</b> and <b>Mo</b>_<b>6</b><b>(Zol)</b>_<b>2</b> contain two trinuclear Mo^VI cores which can rotate around a central oxo group while <b>Mo­(Ale)</b>_<b>2</b> and <b>W­(Ale)</b>_<b>2</b> are mononuclear species. In <b>V</b>_<b>5</b><b>(Ale)</b>_<b>2</b> and <b>V</b>_<b>5</b><b>(Zol)</b>_<b>2</b> a central V^IV ion is surrounded by two V^V dimers bound to bisphosphonate ligands. <b>V</b>_<b>6</b><b>(Ale)</b>_<b>4</b> can be viewed as the condensation of one <b>V</b>_<b>5</b><b>(Ale)</b>_<b>2</b> with one additional V^IV ion and two Ale ligands, while <b>V</b>_<b>3</b><b>(Zol)</b>_<b>3</b> is a triangular V^IV POM. These new POM bisphosphonates complexes were all characterized by single-crystal X-ray diffraction. The stability of the Mo and W POMs was studied by ³¹P NMR spectroscopy and showed that all compounds except the mononuclear <b>Mo­(Ale)</b>_<b>2</b> and <b>W­(Ale)</b>_<b>2</b> were stable in solution. EPR measurements performed on the vanadium derivatives confirmed the oxidation state of the V ions and evidenced their stability in aqueous solution. Electrochemical studies on <b>V</b>_<b>5</b><b>(Ale)</b>_<b>2</b> and <b>V</b>_<b>5</b><b>(Zol)</b>_<b>2</b> showed reduction of V^V to V^IV, and magnetic susceptibility investigations on <b>V</b>_<b>3</b><b>(Zol)</b>_<b>3</b> enabled a detailed analysis of the magnetic interactions. The presence of zoledronate or vanadium correlated with the most potent activity (IC₅₀∼1–5 μM) against three human tumor cell lines

1D-2D-3D Transformation Synthesis of Hierarchical Metal–Organic Framework Adsorbent for Multicomponent Alkane Separation

A new hierarchical MOF consisting of Cu­(II) centers connected by benzene-tricarboxylates (BTC) is prepared by thermoinduced solid transformation of a dense CuBTC precursor phase. The mechanism of the material formation has been thoroughly elucidated and revealed a transformation of a ribbon-like 1D building unit into 2D layers and finally a 3D network. The new phase contains excess copper, charge compensated by systematic hydroxyl groups, which leads to an open microporous framework with tunable permanent mesoporosity. The new phase is particularly attractive for molecular separation. Energy consumption of adsorptive separation processes can be lowered by using adsorbents that discriminate molecules based on adsorption entropy rather than enthalpy differences. In separation of a 11-component mixture of C₁–C₆ alkanes, the hierarchical phase outperforms the structurally related microporous HKUST-1 as well as silicate-based hierarchical materials. Grand canonical Monte Carlo (GCMC) simulation provides microscopic insight into the structural host–guest interaction, confirming low adsorption enthalpies and significant entropic contributions to the molecular separation. The unique three-dimensional hierarchical structure as well as the systematic presence of Cu­(II) unsaturated coordination sites cause this exceptional behavior