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[EN] The Zr terephthalate MOFs UiO-66 and UiO-66-NH2 have been found to be highly diastereoselective catalysts for the synthesis of a pyrano[3,2-c]quinoline through an inverse electron -demand aza-Diels-Alder [4+2] cycloaddition of an aryl Qmine (formed in situ from aniline and benzaldehyde) and 3,4-dihydro-2H-pyran in one pot, affording the corresponding trans isomer in diastereomeric excesses of 90-95 %. The solids are stable under the reaction conditions and can be reused at least three times without significant loss of activity or diastereoselectivity. ; Financial support from the Generalitat Valenciana (projects Consolider-Ingenio MULTICAT and AICO/2015/065), the Spanish Ministry of Economy and Competitiveness (MINECO) (program Severn Ochoa SEV20120267), and the Spanish Ministry of Science and Innovation (MICINN) (project MAT2014-52085-C2-1-P) is gratefully acknowledged. V. L. R. thanks the Fundacion "La Caixa" for a "La Caixa-Severo Ochoa" Ph. D. Scholarship. This project received funding from the European Union's Horizon 2020 Tesearch and Innovation Programme under the Marie Skolodowska Curie grant agreement number 641887. ; López-Rechac, V.; García Cirujano, F.; Corma Canós, A.; Llabrés I Xamena, FX. (2016). Diastereoselective Synthesis of Pyranoquinolines on Zirconium-Containing UiO-66 Metal-Organic Frameworks. European Journal of Inorganic Chemistry. 27:4512-4516. https://doi.org/10.1002/ejic.201600372 ; S ; 4512 ; 4516 ; 27 ; Li, B., Wang, H., & Chen, B. (2014). Microporous Metal-Organic Frameworks for Gas Separation. Chemistry - An Asian Journal, 9(6), 1474-1498. doi:10.1002/asia.201400031 ; Li, J.-R., Sculley, J., & Zhou, H.-C. (2011). Metal–Organic Frameworks for Separations. Chemical Reviews, 112(2), 869-932. doi:10.1021/cr200190s ; Rodenas, T., Luz, I., Prieto, G., Seoane, B., Miro, H., Corma, A., … Gascon, J. (2014). Metal–organic framework nanosheets in polymer composite materials for gas separation. Nature Materials, 14(1), 48-55. doi:10.1038/nmat4113 ; Corma, A., García, H., & ...

[EN] Zirconium terephthalate UiO-66 type metal organic frameworks (MOFs) are known to be highly active, stable and reusable catalysts for the esterification of carboxylic acids with alcohols. Moreover, when defects are present in the structure of these MOFs, coordinatively unsaturated Zr ions with Lewis acid properties are created, which increase the catalytic activity of the resulting defective solids. In the present work, molecular modeling techniques combined with new experimental data on various defective hydrated and dehydrated materials allow to unravel the nature and role of defective active sites in the Fischer esterification and the role of coordinated water molecules to provide additional Bronsted sites. Periodic models of UiO-66 and UiO-66-NH2 catalysts have been used to unravel the reaction mechanism on hydrated and dehydrated materials. Various adsorption modes of water and methanol are investigated. The proposed mechanisms are in line with experimental observations that amino groups yield a reduction in the reaction barriers, although they have a passive role in modulating the electronic structure of the material. Water has a beneficial role on the reaction cycle by providing extra Bronsted sites and by providing stabilization for various intermediates through hydrogen bonds. (C) 2017 The Authors. Published by Elsevier Inc. ; This work is supported by the Fund for Scientific Research Flanders (FWO) (project number 3G048612), the Research Board of Ghent University (BOF) and BELSPO in the frame of IAP/7/05. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 641887 (project acronym: DEFNET). Funding was also received from the European Union's Horizon 2020 research and innovation programme [consolidator ERC grant agreement no. 647755-DYNPOR (2015-2020)]. Computational resources (Stevin Supercomputer Infrastructure) and services were provided by Ghent University. Financial support from the ...

401 414 352 ; S ; [EN] Zirconium terephthalate UiO-66 type metal organic frameworks (MOFs) are known to be highly active, stable and reusable catalysts for the esterification of carboxylic acids with alcohols. Moreover, when defects are present in the structure of these MOFs, coordinatively unsaturated Zr ions with Lewis acid properties are created, which increase the catalytic activity of the resulting defective solids. In the present work, molecular modeling techniques combined with new experimental data on various defective hydrated and dehydrated materials allow to unravel the nature and role of defective active sites in the Fischer esterification and the role of coordinated water molecules to provide additional Bronsted sites. Periodic models of UiO-66 and UiO-66-NH2 catalysts have been used to unravel the reaction mechanism on hydrated and dehydrated materials. Various adsorption modes of water and methanol are investigated. The proposed mechanisms are in line with experimental observations that amino groups yield a reduction in the reaction barriers, although they have a passive role in modulating the electronic structure of the material. Water has a beneficial role on the reaction cycle by providing extra Bronsted sites and by providing stabilization for various intermediates through hydrogen bonds. (C) 2017 The Authors. Published by Elsevier Inc. This work is supported by the Fund for Scientific Research Flanders (FWO) (project number 3G048612), the Research Board of Ghent University (BOF) and BELSPO in the frame of IAP/7/05. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 641887 (project acronym: DEFNET). Funding was also received from the European Union's Horizon 2020 research and innovation programme [consolidator ERC grant agreement no. 647755-DYNPOR (2015-2020)]. Computational resources (Stevin Supercomputer Infrastructure) and services were provided by Ghent University. Financial support ...

[EN] A postsynthetic treatment with diluted solutions of the inorganic HCl or H2SO4 acids was applied to functionalize the eight connected Zr-based metal-organic framework DUT-67 (DUT = Dresden University of Technology). During the treatment, it is possible to remove and exchange the pristine modulator (formate) by Cl(-)or SO(4)(2-)anions. The position of the chlorine in the crystal structure of DUT-67 after HCl treatment could be determined by single-crystal X-ray diffraction analysis. Moreover, by means of the acidic treatment the polarity of the network as well as its Bronsted acid strength are increased, which have a crucial impact on the catalytic performance. The improved catalytic activity of the acid-treated materials was demonstrated in the esterification of levulinic acid with ethanol. ; This project received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant No. 641887 (project acronym: DEFNET). The Spanish Ministry of Economy and Competitiveness (program "Severo Ochoa"), the Spanish Ministry of Science and Innovation (Project No. MAT2014-52085-C2-1-P), and the German Research Foundation (Project No. KA 1698/19-1) are also acknowledged for financial support. ; Drache, F.; García Cirujano, F.; Nguyen, KD.; Bon, V.; Senkovska, I.; Llabrés I Xamena, FX.; Kaskel, S. (2018). Anion Exchange and Catalytic Functionalization of the Zirconium-Based Metal-Organic Framework DUT-67. Crystal Growth & Design. 18(9):5492-5500. https://doi.org/10.1021/acs.cgd.8b00832 ; S ; 5492 ; 5500 ; 18 ; 9