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

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

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