Suchergebnisse

We show a facile method to prepare surface-clean monodispersed small and stable CuOx nanoparticles with controllable average sizes from below 1 nm up to ∼5 nm without using bulk capping agent. Structural and surface characterizations show that the chemical states of CuOx nanoparticles and their interactions with O are dependent on the particle size. To show their relevance to catalysis, the well-defined monodispersed CuOx nanoparticles have been used for oxidative coupling of alkynes. While the generally used CuCl catalysts presents a reaction induction period and agglomerate into CuOx nanoparticles during the reaction, the induction period disappears when monodispersed CuOx nanoparticles (∼2 nm) were used as catalyst. Supported CuOx nanoparticles on TiO behave in the same way as monodispersed CuOx nanoparticles. Kinetic, spectroscopic, and isotopic studies show that O activation is the rate-controlling step and that the nature of the oxygen species formed on supported CuOx nanoparticles is dependent on the size of CuOx and determine the catalytic properties for oxidative coupling of alkynes. ; Financial supports from ConsoliderIngenio 2010 (project MULTICAT) and "Severo Ochoa" program are also gratefully acknowledged. The European Union is also acknowledged by ERC-AdG-2014-671093 - SynCatMatch. ; Peer Reviewed

The Pt-catalysed addition of silanes to functional groups such as alkenes, alkynes, carbonyls and alcohols, i.e. the hydrosilylation reaction, is a fundamental transformation in industrial and academic chemistry, often claimed as the most important application of Pt catalysts in solution. However, the exact nature of the Pt active species and its mechanism of action is not well understood yet, particularly regarding regioselectivity. Here, experimental and computational studies together with an ad hoc graphical method show that the hydroaddition of alkynes proceeds through Pt-Si-H clusters of 3-5 atoms (metal(oid) association) in parts per million amounts (ppm), which decrease the energy of the transition state and direct the regioselectivity of the reaction. Based on these findings, new extremely-active (ppm) microporous solid catalysts for the hydrosilylation of alkynes, alkenes and alcohols have been developed, paving the way for more environmentally-benign industrial applications. This journal is ; Financial support by MINECO through the Severo Ochoa program (SEV-2016-0683), Excellence program (CTQ 2017-86735-P and CTQ 2017-87974-R) and Retos Col. (RTC-2017-6331-5) is acknowledged. E. P. acknowledges the financial support of the European Research Council under the European Union's Horizon 2020 research and innovation program/ERC Grant Agreement No. 814804, MOF-reactors. M. A. R.-C. thanks ITQ for the concession of a contract and J. O. M. thanks the Juan de la Cierva program for the concession of a contract. We thank V. B. dLL. and N. G. G. for performing degree projects in the ITQ labs. This research was partially supported by the supercomputing infrastructure of Poznan Supercomputing Center. The Electron Microscopy Service of the UPV is also acknowledged.

The exact chemical structure of non–crystallising natural products is still one of the main challenges in Natural Sciences. Despite tremendous advances in total synthesis, the absolute structural determination of a myriad of natural products with very sensitive chemical functionalities remains undone. Here, we show that a metal–organic framework (MOF) with alcohol–containing arms and adsorbed water, enables selective hydrolysis of glycosyl bonds, supramolecular order with the so–formed chiral fragments and absolute determination of the organic structure by single–crystal X–ray crystallography in a single operation. This combined strategy based on a biomimetic, cheap, robust and multigram available solid catalyst opens the door to determine the absolute configuration of ketal compounds regardless degradation sensitiveness, and also to design extremely–mild metal–free solid–catalysed processes without formal acid protons. ; This work was supported by the Ministero dell'Istruzione, dell'Università e della Ricerca (Italy) and the MINECO (Spain) (Projects CTQ2016-75671-P, CTQ 2017-86735-P, RTC-2017-6331-5, Severo Ochoa program SEV-2016-0683 and Excellence Unit "Maria de Maeztu" MDM-2015-0538). R.B. thanks the MIUR (Project PON R&I FSE-FESR 2014–2020) for grant. L.B wishes to thank Italian MIUR for grant n. AIM1899391–1 in the framework of the project "Azione I.2, Mobilità dei Ricercatori, PON R&I 2014–2020". Thanks are also extended to the "2019 Post-doctoral Junior Leader-Retaining Fellowship, la Caixa Foundation (ID100010434 and fellowship code LCF/BQ/PR19/11700011" (J. F.- S.). S. S.-N. thanks ITQ for the concession of a contract. D.A. acknowledges the financial support of the Fondazione CARIPLO/"Economia Circolare: ricerca per un futuro sostenibile" 2019, Project code: 2019–2090, MOCA. E.P. acknowledges the financial support of the European Research Council under the European Union's Horizon 2020 research and innovation program/ERC Grant Agreement No. 814804, MOF-reactors.

Supramolecular coordination compounds (SCCs) represent the power of coordination chemistry methodologies to self-assemble discrete architectures with targeted properties. SCCs are generally synthesized in solution, with isolated fully coordinated metal atoms as structural nodes, thus severely limited as metal-based catalysts. Metal-organic frameworks (MOFs) show unique features to act as chemical nanoreactors for the in situ synthesis and stabilization of otherwise not accessible functional species. Here, we present the self-assembly of PdII SCCs within the confined space of a pre-formed MOF (SCCs@MOF) and its post-assembly metalation to give a PdII-AuIII supramolecular assembly, crystallography underpinned. These SCCs@MOFs catalyze the coupling of boronic acids and/or alkynes, representative multi-site metal-catalyzed reactions in which traditional SCCs tend to decompose, and retain their structural integrity as a consequence of the synergetic hybridization between SCCs and MOFs. These results open new avenues in both the synthesis of novel SCCs and their use in heterogeneous metal-based supramolecular catalysis. ; This work was supported by the MINECO (Spain) (Projects CTQ2016-75671-P and 2017-86735-P, and Excellence Units "Severo Ochoa" and "Maria de Maeztu" SEV-2016-0683 and MDM-2015-0538), the Ministero dell'Istruzione, dell'Università e della Ricerca (Italy), and the Engineering and Physical Sciences Research Council (UK). M.M. thanks the MINECO for a predoctoral contract. R.A. thanks UPV and R.G. thanks ITQ for the corresponding contracts. D.A. thanks the "Fondo per il finanziamento delle attività base di ricerca". E.P. acknowledges financial support from the European Research Council under the European Union's Horizon 2020 research and innovation programme/ERC Grant Agreement No. 814804, MOF-reactors. Thanks are also extended to the "Subprograma Atracció de Talent-Contractes Post-doctorals de la Universitat de Valencia" and the "2018 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation" (J.F.-S.). We thank the Diamond Light Source for awarded beamtime (proposal number MT18768) and provision of synchrotron radiation facility, and Dr. David Allan and Dr. Sarah Barnett for their assistance at the I19 beamline.

The chemical bulk reductive covalent functionalization of thin-layer black phosphorus (BP) using BP intercalation compounds has been developed. Through effective reductive activation, covalent functionalization of the charged BP by reaction with organic alkyl halides is achieved. Functionalization was extensively demonstrated by means of several spectroscopic techniques and DFT calculations; the products showed higher functionalization degrees than those obtained by neutral routes. ; A.H. and G.A. acknowledge the European Research Council (ERC Advanced Grant 742145 B‐PhosphoChem to A.H., and ERC Starting Grant 2D‐PnictoChem 804110 to G.A.) for support. The research leading to these results was partially funded by the European Union Seventh Framework Programme under grant agreement No. 604391 Graphene Flagship. G.A. has received financial support through the Postdoctoral Junior Leader Fellowship Programme from "la Caixa" Banking Foundation (LCF/BQ/PI18/11630018). G.A. thanks the Deutsche Forschungsgemeinschaft (DFG; FLAG‐ERA AB694/2‐1), the Generalitat Valenciana (SEJI/2018/034 grant), and the FAU (Emerging Talents Initiative grant #WS16‐17_Nat_04) for support. A.H. and A.G. thank the SFB 953 "Synthetic Carbon Allotropes" funded by the DFG for support and the Cluster of Excellence "Engineering of Advanced Materials". A.G. is grateful for funding from the Free State of Bavaria (Research Network "Solar Technologies go Hybrid"). A.M. thanks the Alexander von Humboldt (AvH) Foundation for a postdoctoral fellowship. This work was supported by the MINECO (Spain) through the Excellence Unit María de Maeztu (MDM‐2015‐0538) and the Project CTQ2017‐86735‐P.