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

Immobilization of a Full Photosystem in the Large-Pore MIL-101 Metal-Organic Framework for CO2 reduction

SSCI-VIDE+CARE:ING+XWG:FWI:JECInternational audienceA molecular catalyst [Cp*Rh(4,4′‐bpydc)]2+ and a molecular photosensitizer [Ru(bpy)2(4,4′‐bpydc)]2+ (bpydc=bipyridinedicarboxylic acid) were co‐immobilized into the highly porous metal–organic framework MIL‐101‐NH2(Al) upon easy postsynthetic impregnation. The Rh–Ru@MIL‐101‐NH2 composite allows the reduction of CO2 under visible light, while exhibiting remarkable selectivity with the exclusive production of formate. This Rh–Ru@MIL‐101‐NH2 solid represents the first example of MOFs functionalized with both a catalyst and a photosensitizer in a noncovalent fashion. Thanks to the coconfinement of the catalyst and photosensitizer into the cavity's nanospace, the MOF pores are used as nanoreactors and enable molecular catalysis in a heterogeneous manner

photocatalytic system based on rh-functionalized metal-organic framework

SSCI-VIDE+ING+JEC:DFAInternational audienceMetal-Organic-Frameworks appear to be appealing platforms for immobilization of single-site organometallic catalysts. The first photosensitization of a rhodium-based catalytic system for CO2 reduction is reported, with formate as the sole carbon-containing product. Through post-synthetic ligand exchange methodology, we successfully proceeded to the heterogenization of this molecular catalyst via the synthesis of a new metal-organic framework (MOF) Cp*Rh@UiO-67. While the catalytic activities of the homogeneous and heterogeneous systems are found to be comparable, the MOF-based system is more stable and more selective for formate. Through the study of the behaviour of MOF systems having a controlled Rh loading, competitive catalytic reaction occurring inside the Cp*Rh@UiO-67 framework are postulated. Finally, a combined computational-experimetnal methodology allowed unravelling the band-gap as a new descriptor of the chemical compostion of the hybrid material, to assess ultimately the covalent incorporation of the organometallic catalyst within the framework

Computational design and prediction of interesting not-yet- synthesized structures of inorganic materials by using building unit concepts

The computational design of new and interesting inorganic materials is still an ongoing challenge. The motivation of these efforts is to aid the often difficult task of crystal structure determination, to rationalize different but related structure types, or to help limit the domain of structures that are possible in a given system. Over the past decade, simulation methods have continuously evolved towards the prediction of new structures using minimal input information in terms of symmetry, cell parameters, or chemical composition. So far, this task of identifying candidate structures through an analysis of the energy landscape of chemical systems has been particularly successful for predominantly ionic systems with relatively small numbers of atoms or ions in the simulation cell. After an introductory section, the second section of this work presents the historical developments of such simulation methods in this area. The following sections of the work are dedicated to the introduction of the building unit concept in simulation methods: we present simulation approaches to structure prediction employing both primary (aggregate of atoms) and secondary (aggregate of coordination polyhedra) building units. While structure prediction with primary units is a straightforward extension of established approaches, the AASBU method (automated asssembly of secondary building units) focusses on the topology of network-based structures. This method explores the possible ways to assemble predefined inorganic building units in three-dimensional space, opening the way to the manipulation of very large building units (up to 84 atoms in this work). As illustrative examples we present the prediction of candidate structures for Li4CO4, the identification of topological relationships within a family of metalphosphates, ULM-n and MIL-n, and finally the generation of new topologies by using predefined large building units such as a sodalite or a double-four-ring cage, for the prediction of new and interesting zeolite-type structures

Multicomponent Microporous Polymers as Photosystems for Everlasting CO2 Reduction

SSCI-VIDE+ING+FWI:DFA:JECInternational 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.[1–4]Amongst the catalytic applications, photochemical reactions such as CO2 reduction are of great interest as routes to different value-added C1-molecules, which have high potential as renewable energy sources. Although many efforts on increasing the catalytic efficiency have been achieved, typical catalytic photosystems suffer from low long-term stability or selectivity. Here, we will present a set of fully heterogeneous photosystems for the photocatalytic reduction of CO2 using visible light in the absence of any external photosensitizer. In these materials, the light harvesting moieties are directly enchased in the material structure and tethered to the catalytically active rhodium complexes. These new types of heterogeneous photocatalysts allow a constant and efficient transformation of CO2 into formate with production rates of up to 700 µmol formate per gram of catalyst per hour without any deactivation for at least 4 days, a superior performance with respect to state of the art. We explain their superior performance by a combination of stable organic dyes used as photosensitizer under the visible light, a well-adapted electron density on the active site by a rational choice of the porous framework and an optimized charge separation. We will demonstrate, using in-situ transient spectroscopy, that upon metalation, the excited states of the fully heterogeneous photosystems are effectively quenched resulting in a decrease of their life-times. DFT calculations show that the LUMO of the fully heterogeneous photosystem is centered on the Rh-based catalyst. This allows for an efficient electron transfer from the photosensitizer to the catalytically active Rh and, as a result, helps to stabilize the charge-separated states. References[1]A. Corma, H. García, F. X. Llabrés i Xamena, Chem. Rev. 2010, 110, 4606–4655.[2]C. Kaes, A. Katz, M. W. Hosseini, Chem. Rev. 2000, 100, 3553–3590.[3]F. M. Wisser, P. Berruyer, L. Cardenas, Y. Mohr, E. A. Quadrelli, A. Lesage, D. Farrusseng, J. Canivet, ACS Catal. 2018, 8, 1653–1661.[4]F. M. Wisser, Y. Mohr, E. A. Quadrelli, D. Farrusseng, J. Canivet, ChemCatChem 2018, 10, 1778–1782

Heterogenisation of polyoxometalates and other metal-based complexes in metal–organic frameworks: from synthesis to characterisation and applications in catalysis

International audienceThese last years have seen a huge growing interest in the heterogenisation of molecular catalysts since it allows combining the advantages of homogeneous and heterogeneous catalysis. Besides bringing recyclability, the immobilisation of the catalyst may increase its stability while allowing tuning its selectivity. In this respect, Metal-Organic Frameworks (MOFs) attract an evergrowing interest as a platform for their confinement within their pores or channels. In this review, Cat@MOF composites whereby molecular catalysts (Cats) are immobilised in MOFs through non-covalent interactions with their host, are reviewed thoroughly. Polyoxometalates (POMs) and other metal-based complexes as immobilised molecular species are covered. In the first part, the different synthetic methods and analytical tools are described. A critical analysis of the various physico-chemical methods available to characterise the Cat@MOF composites is provided-a particular attention being paid toward their pertinence for the investigation of the content, the position and the stability of the catalyst within the MOF. Besides, focus is made on non-conventional techniques such as Pair Distribution Function (PDF) and a section is dedicated to the contribution of DFT calculations. In the second part, the applications of these materials in the fields of catalysis, including oxidation and reduction reactions, acid-base catalysis, photo-and electrocatalysis are detailed

Boosting photochemical reduction of CO2 to formic acid catalyzed by porphyrinic MOF-545

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