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1.
Nat Commun ; 11(1): 3080, 2020 06 17.
Artigo em Inglês | MEDLINE | ID: mdl-32555154

RESUMO

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.


Assuntos
Produtos Biológicos/química , Hidrolases/química , Estruturas Metalorgânicas/química , Adsorção , Álcoois/química , Catálise , Cristalografia por Raios X , Glicólise , Hidrólise , Cinética , Metais , Conformação Molecular , Estrutura Molecular , Porosidade , Relação Estrutura-Atividade , Difração de Raios X
2.
Mikrochim Acta ; 187(4): 201, 2020 03 05.
Artigo em Inglês | MEDLINE | ID: mdl-32140827

RESUMO

A bio-metal-organic framework (bio-MOF) derived from the amino acid L-serine has been prepared in bulk form and evaluated as sorbent for the molecular recognition and extraction of B-vitamins. The functional pores of bio-MOF exhibit high amounts of hydroxyl groups jointly directing other supramolecular host-guest interactions thus providing the recognition of B-vitamins in fruit juices and energy drinks. Single-crystal X-ray diffraction studies reveal the specific B-vitamin binding sites and the existence of multiple hydrogen bonds between these target molecules and the framework. It offered unique snapshots to accomplish an efficient capture of these solutes in complex aqueous matrices. Four B-vitamins (thiamin, nicotinic acid, nicotinamide, and pyridoxine) were investigated. They were eluted from the sorbent with phosphate buffer at pH 7 and analyzed by HPLC with UV detection. The sorbent was compared with commercial C18 cartridges. Following the procedure, acceptable reproducibility (RSD values < 14%) was achieved, and the detection limits were in the range 0.4 to 1.4 ng mL-1. The method was applied to the analysis of energy drink and juice samples and the recoveries were between 75 and 123% in spiked beverage samples. Graphical abstractA bio-MOF as SPE sorbent was prepared and applied to the extraction of B-vitamins in fruit juices and energy drinks.

3.
Acc Chem Res ; 53(2): 520-531, 2020 02 18.
Artigo em Inglês | MEDLINE | ID: mdl-32027486

RESUMO

Since the advent of the first metal-organic frameworks (MOFs), we have witnessed an explosion of captivating architectures with exciting physicochemical properties and applications in a wide range of fields. This, in part, can be understood under the light of their rich host-guest chemistry and the possibility to use single-crystal X-ray diffraction (SC-XRD) as a basic characterization tool. Moreover, chemistry on preformed MOFs, applying recent developments in template-directed synthesis and postsynthetic methodologies (PSMs), has shown to be a powerful synthetic tool to (i) tailor MOFs channels of known topology via single-crystal to single-crystal (SC-SC) processes, (ii) impart higher degrees of complexity and heterogeneity within them, and most importantly, (iii) improve their capabilities toward applications with respect to the parent MOFs. However, the unique properties of MOFs have been, somehow, limited and underestimated. This is clearly reflected on the use of MOFs as chemical nanoreactors, which has been barely uncovered. In this Account, we bring together our recent advances on the construction of MOFs with appealing properties to act as chemical nanoreactors and be used to synthesize and stabilize, within their channels, catalytically active species that otherwise could be hardly accessible. First, through two relevant examples, we present the potential of the metalloligand approach to build highly robust and crystalline oxamato- and oxamidato-MOFs with tailored channels, in terms of size, charge and functionality. These are initial requisites to have a playground where we can develop and fully take advantage of singular properties of MOFs as well as visualize/understand the processes that take place within MOFs pores and somehow make structure-functionalities correlations and develop more performant MOFs nanoreactors. Then, we describe how to exploit the unique and singular features that offer each of these MOFs confined space for (i) the incorporation and stabilization of metals salts and complexes, (ii) the in situ stepwise synthesis of subnanometric metal clusters (SNMCs), and (iii) the confined-space self-assembly of supramolecular coordination complexes (SCCs), by means of PSMs and underpinned by SC-XRD. The strategy outlined here has led to unique rewards such as the highly challenging gram-scale preparation of stable and well-defined ligand-free SNMCs, exhibiting outstanding catalytic activities, and the preparation of unique SCCs, different to those assembled in solution, with enhanced stabilities, catalytic activities, recyclabilities, and selectivities. The results presented in this Accounts are just a few recent examples, but highly encouraging, of the large potential way of MOFs acting as chemical nanoreactors. More work is needed to found the boundaries and fully understand the chemistry in the confined space. In this sense, mastering the synthetic chemistry of discrete organic molecules and inorganic complexes has basically changed our way of live. Thus, achieving the same degree of control on extended hybrid networks will open new frontiers of knowledge with unforeseen possibilities. We aim to stimulate the interest of researchers working in broadly different fields to fully unleash the host-guest chemistry in MOFs as chemical nanoreactors with exclusive functional species.

4.
Inorg Chem ; 58(21): 14498-14506, 2019 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-31621305

RESUMO

Achieving fine control on the structure of metal-organic frameworks (MOFs) is mandatory to obtain target physical properties. Herein, we present how the combination of a metalloligand approach and a postsynthetic method is a suitable and highly useful synthetic strategy to success on this extremely difficult task. First, a novel oxamato-based tetranuclear cobalt(III) compound with a tetrahedron-shaped geometry is used, for the first time, as the metalloligand toward calcium(II) metal ions to lead to a diamagnetic CaII-CoIII three-dimensional (3D) MOF (1). In a second stage, in a single-crystal-to-single-crystal manner, the calcium(II) ions are replaced by terbium(III), dysprosium(III), holmium(III), and erbium(III) ions to yield four isostructural novel LnIII-CoIII [Ln = Tb (2), Dy (3), Ho (4), and Er (5)] 3D MOFs. Direct-current magnetic properties for 2-5 show typical performances for the ground-state terms of the lanthanoid cations [7F6 (TbIII), 6H15/2 (DyIII), 5I8 (HoIII), and 4I15/2 (ErIII)]. Analysis of the χMT data indicates that the ground state is the lowest MJ value, that is, MJ = 0 (2 and 4) and ±1/2 (3 and 5). Kramers' ions (3 and 5) exhibit field-induced emergent frequency-dependent alternating-current magnetic susceptibility signals, which is indicative of the presence of slow magnetic relaxation typical of single-molecule magnets.

5.
J Am Chem Soc ; 141(34): 13601-13609, 2019 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-31394030

RESUMO

We report a new water-stable multivariate (MTV) metal-organic framework (MOF) prepared by combining two different oxamide-based metalloligands derived from the natural amino acids l-serine and l-methionine. This unique material features hexagonal channels decorated with two types of flexible and functional "arms" (-CH2OH and -CH2CH2SCH3) capable of enabling, synergistically, the simultaneous and efficient removal of both inorganic (heavy metals such as Hg2+, Pb2+, and Tl+) and organic (dyes such as Pyronin Y, Auramine O, Brilliant green, and Methylene blue) contaminants, and, in addition, this MTV-MOF is completely reusable. Single-crystal X-ray diffraction measurements allowed solving the crystal structure of a host-guest adsorbate, containing both HgCl2 and Methylene blue, and offered unprecedented snapshots of this unique dual capture process. This is the very first time that a MOF can be used for the removal of all sorts of pollutants from water resources, thus opening new perspectives for this emerging type of MTV-MOF.

6.
J Am Chem Soc ; 141(26): 10350-10360, 2019 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-31194534

RESUMO

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.

7.
Angew Chem Int Ed Engl ; 57(52): 17094-17099, 2018 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-30398300

RESUMO

The synthesis and reactivity of single metal atoms in a low-valence state bound to just water, rather than to organic ligands or surfaces, is a major experimental challenge. Herein, we show a gram-scale wet synthesis of Pt1 1+ stabilized in a confined space by a crystallographically well-defined first water sphere, and with a second coordination sphere linked to a metal-organic framework (MOF) through electrostatic and H-bonding interactions. The role of the water cluster is not only isolating and stabilizing the Pt atoms, but also regulating the charge of the metal and the adsorption of reactants. This is shown for the low-temperature water-gas shift reaction (WGSR: CO + H2 O → CO2 + H2 ), where both metal coordinated and H-bonded water molecules trigger a double water attack mechanism to CO and give CO2 with both oxygen atoms coming from water. The stabilized Pt1+ single sites allow performing the WGSR at temperatures as low as 50 °C.

8.
Inorg Chem ; 57(21): 13895-13900, 2018 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-30351058

RESUMO

We report two new highly crystalline metal-organic frameworks (MOFs), derived from the natural amino acids serine (1) and threonine (2), featuring hexagonal channels densely decorated with hydroxyl groups belonging to the amino acid residues. Both 1 and 2 are capable of discriminating, via solid-phase extraction, a mixture of selected chloride salts of lanthanides on the basis of their size, chemical affinity, and/or the flexibility of the network. In addition, this discrimination follows a completely different trend for 1 and 2 because of the different locations of the hydroxyl groups in each compound, which is evocative of steric complementarity between the substrate and receptor. Last but not least, the crystal structures of selected adsorbates could be resolved, offering unprecedented snapshots on the capture process and enabling structural correlations with the separation mechanism.

9.
Chemistry ; 24(67): 17712-17718, 2018 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-30084504

RESUMO

The presence of residual organic dyes in water resources or wastewater treatment systems, derived mainly from effluents of different industries, is a major environmental problem with no easy solution. Herein, an ecofriendly, water-stable metal-organic framework was prepared from a derivative of the natural amino acid l-serine. Its functional channels are densely decorated with highly flexible l-serine residues bearing hydroxyl groups. The presence of such a flexible and functional environment within the confined environment of the MOF leads to efficient removal of different organic dyes from water: Pyronin Y, Auramine O, Methylene Blue and Brilliant Green, as unveiled by unprecedented snapshots offered by single-crystal X-ray diffraction. This MOF enables highly efficient water remediation by capturing more than 90 % of dye content, even at very low concentrations such as 10 ppm, which is similar to those usually found in industrial wastewaters. Remarkably, the removal efficiency is improved in simulated contaminated mineral water with multiple dyes.

10.
Chem Commun (Camb) ; 54(65): 9063-9066, 2018 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-30052246

RESUMO

We report the application of a post-synthetic solid-state cation-exchange process to afford a novel 3D MOF with hydrated barium cations hosted at pores able to trigger selective and reversible SO2 adsorption. Computational modelling supports the full reversibility of the adsorption process on the basis of weak supramolecular interactions between SO2 and coordinated water molecules.

11.
J Am Chem Soc ; 140(28): 8827-8832, 2018 07 18.
Artigo em Inglês | MEDLINE | ID: mdl-29940112

RESUMO

The search for simple, earth-abundant, cheap, and nontoxic metal catalysts able to perform industrial hydrogenations is a topic of interest, transversal to many catalytic processes. Here, we show that isolated FeIII-O sites on solids are able to dissociate and chemoselectively transfer H2 to acetylene in an industrial process. For that, a novel, robust, and highly crystalline metal-organic framework (MOF), embedding FeIII-OH2 single sites within its pores, was prepared in multigram scale and used as an efficient catalyst for the hydrogenation of 1% acetylene in ethylene streams under front-end conditions. Cutting-edge X-ray crystallography allowed the resolution of the crystal structure and snapshotted the single-atom nature of the catalytic FeIII-O site. Translation of the active site concept to even more robust and inexpensive titania and zirconia supports enabled the industrially relevant hydrogenation of acetylene with similar activity to the Pd-catalyzed process.

12.
Angew Chem Int Ed Engl ; 57(21): 6186-6191, 2018 05 22.
Artigo em Inglês | MEDLINE | ID: mdl-29600831

RESUMO

The gram-scale synthesis, stabilization, and characterization of well-defined ultrasmall subnanometric catalytic clusters on solids is a challenge. The chemical synthesis and X-ray snapshots of Pt02 clusters, homogenously distributed and densely packaged within the channels of a metal-organic framework, is presented. This hybrid material catalyzes efficiently, and even more importantly from an economic and environmental viewpoint, at low temperature (25 to 140 °C), energetically costly industrial reactions in the gas phase such as HCN production, CO2 methanation, and alkene hydrogenations. These results open the way for the design of precisely defined catalytically active ultrasmall metal clusters in solids for technically easier, cheaper, and dramatically less-dangerous industrial reactions.

13.
Dalton Trans ; 46(43): 15130-15137, 2017 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-29068025

RESUMO

A novel three-dimensional (3D) coordination polymer with the formula (C3N2H5)4[MnCr2(ox)6]·5H2O (2), where ox = oxalate and C3N2H5 = imidazolium cation, is reported. Single crystal X-ray diffraction reveals that this porous coordination polymer adopts a chiral three-dimensional quartz-like architecture, with the guest imidazolium cations and water molecules being hosted in its pores. This novel multifunctional material exhibits both a ferromagnetic ordering at TC = 3.0 K, related to the host MnCr2 network, and high proton conductivity [1.86 × 10-3 S cm-1 at 295 K and 88% relative humidity (RH)] due to the presence of the acidic imidazolium cations and free water molecules. The similarity of the structure of compound 2 to that of the previously reported analogous compound (NH4)4[MnCr2(ox)6]·4H2O, (1), also allows us to analyse, to a certain extent, the effect of the acidity of the proton donating guest molecules on proton conduction properties. 2 hosts, in one-dimensional (1D) channels, imidazolium cations, which are more acidic than the ammonium ones in 1 and, as a consequence, 2 shows higher proton conduction than 1, highlighting the effect of the pKa of the proton donating guest molecules on proton conductivity.

14.
J Am Chem Soc ; 139(24): 8098-8101, 2017 06 21.
Artigo em Inglês | MEDLINE | ID: mdl-28585837

RESUMO

Ferroelectrics (FEs) are materials of paramount importance with a wide diversity of applications. Herein, we propose a postsynthetic methodology for the smart implementation of ferroelectricity in chiral metal-organic frameworks (MOFs): following a single-crystal to single-crystal cation metathesis, the Ca2+ counterions of a preformed chiral MOF of formula Ca6II{CuII24[(S,S)-hismox]12(OH2)3}·212H2O (1), where hismox is a chiral ligand derived from the natural amino acid l-histidine, are replaced by CH3NH3+. The resulting compound, (CH3NH3)12{CuII24[(S,S)-hismox]12(OH2)3}·178H2O (2), retains the polar space group of 1 and is ferroelectric below 260 K. These results open a new synthetic avenue to enlarge the limited number of FE MOFs.

15.
Nat Mater ; 16(7): 760-766, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-28604715

RESUMO

The development of catalysts able to assist industrially important chemical processes is a topic of high importance. In view of the catalytic capabilities of small metal clusters, research efforts are being focused on the synthesis of novel catalysts bearing such active sites. Here we report a heterogeneous catalyst consisting of Pd4 clusters with mixed-valence 0/+1 oxidation states, stabilized and homogeneously organized within the walls of a metal-organic framework (MOF). The resulting solid catalyst outperforms state-of-the-art metal catalysts in carbene-mediated reactions of diazoacetates, with high yields (>90%) and turnover numbers (up to 100,000). In addition, the MOF-supported Pd4 clusters retain their catalytic activity in repeated batch and flow reactions (>20 cycles). Our findings demonstrate how this synthetic approach may now instruct the future design of heterogeneous catalysts with advantageous reaction capabilities for other important processes.

16.
Angew Chem Int Ed Engl ; 55(37): 11167-72, 2016 09 05.
Artigo em Inglês | MEDLINE | ID: mdl-27529544

RESUMO

A robust and water-stable metal-organic framework (MOF), featuring hexagonal channels decorated with methionine residues (1), selectively captures toxic species such as CH3 Hg(+) and Hg(2+) from water. 1 exhibits the largest Hg(2+) uptake capacity ever reported for a MOF, decreasing the [Hg(2+) ] and [CH3 Hg(+) ] concentrations in potable water from highly hazardous 10 ppm to the much safer values of 6 and 27 ppb, respectively. Just like with biological systems, the high-performance metal capture also involves a molecular recognition process. Both CH3 Hg(+) and Hg(2+) are efficiently immobilized by specific conformations adopted by the flexible thioether "claws" decorating the pores of 1. This leads to very stable structural conformations reminiscent of those responsible for the biological activity of the enzyme mercury reductase (MR).

17.
Inorg Chem ; 55(14): 6845-7, 2016 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-27387762

RESUMO

The old but evergreen family of bimetallic oxalates still offers innovative and interesting results. When (Me4N)3[Cr(ox)3]·3H2O is reacted with Mn(II) ions in a nonaqueous solvent, a novel three-dimensional magnet of the formula [N(CH3)4]6[Mn3Cr4(ox)12]·6CH3OH is obtained instead of the one-dimensional compound obtained in water. This new material exhibits an unprecedented stoichiometry with a binodal (3,4) net topology and the highest critical temperature (TC = 7 K) observed so far in a manganese-chromium oxalate based magnet.

18.
J Am Chem Soc ; 138(25): 7864-7, 2016 06 29.
Artigo em Inglês | MEDLINE | ID: mdl-27295383

RESUMO

A novel chiral 3D bioMOF exhibiting functional channels with thio-alkyl chains derived from the natural amino acid l-methionine (1) has been rationally prepared. The well-known strong affinity of gold for sulfur derivatives, together with the extremely high flexibility of the thioether "arms" decorating the channels, account for a selective capture of gold(III) and gold(I) salts in the presence of other metal cations typically found in electronic wastes. The X-ray single-crystal structures of the different gold adsorbates Au(III)@1 and Au(I)@1 suggest that the selective metal capture occurs in a metal ion recognition process somehow mimicking what happens in biological systems and protein receptors. Both Au(III)@1 and Au(I)@1 display high activity as heterogeneous catalyst for the hydroalkoxylation of alkynes, further expanding the application of these novel hybrid materials.

20.
Chemistry ; 22(2): 539-45, 2016 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-26603579

RESUMO

Single-ion magnets (SIMs) are the smallest possible magnetic devices and are a controllable, bottom-up approach to nanoscale magnetism with potential applications in quantum computing and high-density information storage. In this work, we take advantage of the promising, but yet insufficiently explored, solid-state chemistry of metal-organic frameworks (MOFs) to report the single-crystal to single-crystal inclusion of such molecular nanomagnets within the pores of a magnetic MOF. The resulting host-guest supramolecular aggregate is used as a playground in the first in-depth study on the interplay between the internal magnetic field created by the long-range magnetic ordering of the structured MOF and the slow magnetic relaxation of the SIM.

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