Thermodynamic and kinetic factors in the hydrothermal synthesis of hybrid frameworks: zinc 4-cyclohexene-1,2-dicarboxylates

Experimental and computational studies indicate that the formation of a series of zinc 4-cyclohexene-1,2-dicarboxylates takes place under thermodynamic rather than kinetic control

Connecting defects and amorphization in UiO-66 and MIL-140 metal-organic frameworks: a combined experimental and computational study.

The mechanism and products of the structural collapse of the metal-organic frameworks (MOFs) , and upon ball-milling are investigated through solid state (13)C NMR and pair distribution function (PDF) studies, finding amorphization to proceed by the breaking of a fraction of metal-ligand bonding in each case. The amorphous products contain inorganic-organic bonding motifs reminiscent of the crystalline phases. Whilst the inorganic Zr6O4(OH)4 clusters of remain intact upon structural collapse, the ZrO backbone of the frameworks undergoes substantial distortion. Density functional theory calculations have been performed to investigate defective models of and show, through comparison of calculated and experimental (13)C NMR spectra, that amorphization and defects in the materials are linked.The manuscript was written through contributions of all authors. TDB conceived the initial project. T.D.B. acknowledges Trinity Hall (University of Cambridge) and Professor Anthony K. Cheetham for use of lab facilities. D.G.R. acknowledges the UK MRC for financial support. The authors acknowledge Diamond Light Source for the provision of synchrotron access to Beamline I15 (ex p. EE9691) and Philip A. Chater and Andrew Cairns for assistance with data collection. T.K.T. and C.M.D. thank the French National Research Agency (ANR project: HOPFAME ANR-13-BS07-0002-01) and the Foundation de l'Orangerie for funding. The calculations have been performed using the HPC resources from GENCI (CINES/TGCC/IDRIS) through Grant (2015-097343 and -091461). B.B., B.V.d.V. and D.D.V . gratefully acknowledge the FWO for funding (aspirant grant).This is the final version of the article. It was first available from the Royal Society of Chemistry via http://dx.doi.org/10.1039/C5CP06798

Exceptionally low shear modulus in a prototypical imidazole-based metal-organic framework.

Using Brillouin scattering, we measured the single-crystal elastic constants (C(ij)'s) of a prototypical metal-organic framework (MOF): zeolitic imidazolate framework (ZIF)-8 [Zn(2-methylimidazolate)(2)], which adopts a zeolitic sodalite topology and exhibits large porosity. Its C(ij)'s under ambient conditions are (in GPa) C(11)=9.522(7), C(12)=6.865(14), and C(44)=0.967(4). Tensorial analysis of the C(ij)'s reveals the complete picture of the anisotropic elasticity in cubic ZIF-8. We show that ZIF-8 has a remarkably low shear modulus G(min) < or approximately 1 GPa, which is the lowest yet reported for a single-crystalline extended solid. Using ab initio calculations, we demonstrate that ZIF-8's C(ij)'s can be reliably predicted, and its elastic deformation mechanism is linked to the pliant ZnN(4) tetrahedra. Our results shed new light on the role of elastic constants in establishing the structural stability of MOF materials and thus their suitability for practical applications

From computational discovery to experimental characterization of a high hole mobility organic crystal

For organic semiconductors to find ubiquitous electronics applications, the development of new materials with high mobility and air stability is critical. Despite the versatility of carbon, exploratory chemical synthesis in the vast chemical space can be hindered by synthetic and characterization difficulties. Here we show that in silico screening of novel derivatives of the dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene semiconductor with high hole mobility and air stability can lead to the discovery of a new high-performance semiconductor. On the basis of estimates from the Marcus theory of charge transfer rates, we identified a novel compound expected to demonstrate a theoretic twofold improvement in mobility over the parent molecule. Synthetic and electrical characterization of the compound is reported with single-crystal field-effect transistors, showing a remarkable saturation and linear mobility of 12.3 and 16 cm2 V−1 s−1, respectively. This is one of the very few organic semiconductors with mobility greater than 10 cm2 V−1 s−1 reported to date

Three-dimensional lanthanide-organic frameworks based on di-, tetra-, and hexameric clusters

Three-dimensional lanthanide-organic frameworks formulated as (CH3)2NH2[Ln(pydc)2] · 1/2H2O [Ln3+ ) Eu3+ (1a) or Er3+ (1b); pydc2- corresponds to the diprotonated residue of 2,5-pyridinedicarboxylic acid (H2pydc)], [Er4(OH)4(pydc)4(H2O)3] ·H2O (2), and [PrIII 2PrIV 1.25O(OH)3(pydc)3] (3) have been isolated from typical solvothermal (1a and 1b in N,N-dimethylformamide - DMF) and hydrothermal (2 and 3) syntheses. Materials were characterized in the solid state using single-crystal X-ray diffraction, thermogravimetric analysis, vibrational spectroscopy (FT-IR and FT-Raman), electron microscopy, and CHN elemental analysis. While synthesis in DMF promotes the formation of centrosymmetric dimeric units, which act as building blocks in the construction of anionic ∞ 3{[Ln(pydc)2]-} frameworks having the channels filled by the charge-balancing (CH3)2NH2 + cations generated in situ by the solvolysis of DMF, the use of water as the solvent medium promotes clustering of the lanthanide centers: structures of 2 and 3 contain instead tetrameric [Er4(μ3-OH)4]8+ and hexameric |Pr6(μ3-O)2(μ3-OH)6| clusters which act as the building blocks of the networks, and are bridged by the H2-xpydcx- residues. It is demonstrated that this modular approach is reflected in the topological nature of the materials inducing 4-, 8-, and 14-connected uninodal networks (the nodes being the centers of gravity of the clusters) with topologies identical to those of diamond (family 1), and framework types bct (for 2) and bcu-x (for 3), respectively. The thermogravimetric studies of compound 3 further reveal a significant weight increase between ambient temperature and 450 °C with this being correlated with the uptake of oxygen from the surrounding environment by the praseodymium oxide inorganic core

Prediction of superior enantioselectivity within a MOF

SSCI-VIDE+ING+JECInternational audienceThe last decade has seen an unprecedented progress in the discovery of new functional porous materials as well as the prediction of their properties. While the reactivity and enantioselectivity of molecular chiral catalysts have been rationalized and ultimately predicted for liquid-phase homogeneous phase reactions, asymmetric transformations associated to the increasing sophistication of MOF-based heterogeneous catalysts structures render computational efforts challenging. Here, in the case of asymmetric catalysis, the role of the MOF in confining the catalyst and in sterically constraining the approach of the substrate at the catalytic site is discussed. The specificities of host-guest interactions in the heterogeneous MOF-based catalyst when compared to those of molecular homogeneous counterparts are highlighted. We will show that computational chemistry can explain and even predict the selectivity in confined asymmetric catalysis within a MOF [1].Computationally generated structures of Al-MIL-101-NH-Gly-Pro containing a benzene ruthenium complex as catalytically active site have been thoroughly analyzed for docking of prochiral substrate. The obtained data gave insights into enantioselective process at play inside the MOF and allowed to predict the selectivity of asymmetric transfer hydrogenation reaction catalyzed within the MOF.Experimentally, the heterogenization of a chiral benzene ruthenium molecular complex within the MIL-101-NH-Gly-Pro [2, 3] cavity allows a threefold enhancement of the selectivity in the catalyzed asymmetric transfer hydrogenation of acetophenone compared to homogenous analogue system. The excellent match between the computational outcomes and observed enantiomeric excesses provides a robust atomic-level rationale for the observed product selectivity.With these unpublished results, DFT-level computations supported by experimental data highlight the crucial role of the MOF as a macroligand [4] for the ruthenium catalyst to direct the enantioselectivity of the reaction. The molecular level understanding towards the prediction of structure-reactivity relationship in hybrid porous solids like MOF allows reaching the same level of rationalization in the design of heterogeneous catalyst than that developed for decades for molecular systems.[5]This work has been carried out within the French ANR projects HOPFAME (ANR-13-BS07-0002-01) and POMAC (ANR-18-CE07-0025-01).References1.J. Canivet et al. Chem. Sci. 11, 8800–8808 (2020).2.J. Bonnefoy et al., J. Am. Chem. Soc. 9409–9416 (2015).3.T.K. Todorova et al., Chem. Eur. J. 22, 16531–16538 (2016).4.F. M. Wisser et al. ACS Catal. 8, 1653–1661 (2018).5.J.P. Reid et al., Nat. Rev. Chem. 2, 290 (2018)

Effect of the MOF Interface on Confined Molecular Asymmetric Catalysis

SSCI-VIDE+ING+JEC:EQDInternational audienceThe last decade has seen an unprecedented progress in the discovery of new functional porous materials as well as the prediction of their properties. While the reactivity and enantioselectivity of molecular chiral catalysts have been rationalized and ultimately predicted for liquid-phase homogeneous phase reactions, asymmetric transformations associated to the increasing sophistication of MOF-based heterogeneous catalysts structures render computational efforts challenging. Here, in the case of asymmetric catalysis, the role of the MOF in confining the catalyst and in sterically constraining the approach of the substrate at the catalytic site is discussed. The specificities of host-guest interactions in the heterogeneous MOF-based catalyst when compared to those of molecular homogeneous counterparts are highlighted. We will show that computational chemistry can explain and even predict the selectivity in confined asymmetric catalysis within a MOF.Computationally generated structures of Al-MIL-101-NH-Gly-Pro containing a benzene ruthenium complex as catalytically active site have been thoroughly analyzed for docking of prochiral substrate. The obtained data gave insights into enantioselective process at play inside the MOF and allowed to predict the selectivity of asymmetric transfer hydrogenation reaction catalyzed within the MOF.Experimentally, the heterogenization of a chiral benzene ruthenium molecular complex within the MIL-101-NH-Gly-Pro [1, 2] cavity allows a threefold enhancement of the selectivity in the catalyzed asymmetric transfer hydrogenation of acetophenone compared to homogenous analogue system. The excellent match between the computational outcomes and observed enantiomeric excesses provides a robust atomic-level rationale for the observed product selectivity.DFT-level computations supported by experimental data highlight the crucial role of the MOF as a macroligand for the ruthenium catalyst to direct the enantioselectivity of the reaction. [3] The molecular level understanding towards the prediction of structure-reactivity relationship in hybrid porous solids like MOF allows reaching the same level of rationalization in the design of heterogeneous catalyst than that developed for decades for molecular systems.[4]This work has been carried out within the French ANR projects HOPFAME (ANR-13-BS07-0002-01) and POMAC (ANR-18-CE07-0025-01). [1] J. Bonnefoy et al., J. Am. Chem. Soc. 9409–9416 (2015). [2] T.K. Todorova et al., Chem. Eur. J. 22, 16531–16538 (2016). [3] J. Canivet et al. Chem. Sci. 11, 8800–8808 (2020). [4] J.P. Reid et al., Nat. Rev. Chem. 2, 290 (2018)

Tailor Made Heterogeneous Photocatalysts for Carbon Dioxide Reduction based on Microporous Macroligands

SSCI-VIDE+ING+FWI:JEC:DFAInternational audienceHeterogeneous catalysis allows to circumvent the problem of separation of the catalyst from the products and to simplify its recyclability. The integration of the catalytically active centers into a solid support without loss of performance compared to the homogeneous analog is still a major challenge. In this context, a molecularly defined support as macroligand, i.e. a solid acting like the ligand in the corresponding molecular complex, can be considered as a key to bridge the gap between molecular and heterogeneous catalysis. In particular, porous frame-works made by the repetition of a coordinating motif, like the bipyridine motif are of a high interest as bipyridines are widely used as chelating ligand for molecular catalysts.[1]Amongst the catalytic applications, photochemical carbon dioxide reduction is of tremendous importance as routes to renewable energy sources. Here we present a series of heteroge-neous photocatalysts based on metal-organic frameworks and microporous polymers used as macroligands for heterogenized organometallic complexes.[2] We show that both homo-geneous and heterogenized catalysts follow the same linear correlation between the elec-tronic effect of the ligand, described by the Hammett parameter, and the catalytic activity. This correlation highlights the crucial impact of the local electronic environment surrounding the active catalytic center over the long-range framework structure of the porous support. The rational design of heterogenized catalysts can thus be guided by molecular chemistry rules. This is demonstrated here for the Rh-catalyzed photoreduction of carbon dioxide into formate with turnover frequencies (TOF) up to 28 h−1, the highest TOFs reported so far for heterogeneous photocatalytic formate production.[2]We will also present completely heterogeneous photocatalysts to overcome the current limi-tation of photodegradation of the light harvesting moiety. In these systems both the photo-sensitizer and the catalyst are integrated into the same framework,[3] thus increasing the long-term stability of the catalyst. In addition, different photosensitizers will be evaluated in terms of their light absorption properties and the resulting catalytic activities.References:[1] a) A. Corma, H. García, F. X. Llabrés i Xamena Chem. Rev. 2010, 110, 4606-4655;b) C. Kaes, A. Katz, M. W. Hosseini Chem. Rev. 2000, 100, 3553-3590.[2] F. M. Wisser, P. Berruyer, L. Cardenas, Y. Mohr, E. A. Quadrelli, A. Lesage, D. Farrusseng, J. Canivet ACS Catal. 2018, 8, 1653-1661.[3] X. Wang, F. M. Wisser, J. Canivet, M. Fontecave, C. Mellot-Draznieks, ChemSusChem, DOI: 10.1002/cssc.20180106