Publications
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A three-shell supramolecular complex enables the symmetry-mismatched chemo- and regioselective bis-functionalization of C60
Ubasart E., Borodin O., Fuertes-Espinosa C., Xu Y., García-Simón C., Gómez L., Juanhuix J., Gándara F., Imaz I., Maspoch D., von Delius M., Ribas X. Nature Chemistry; 13 (5): 420 - 427. 2021. 10.1038/s41557-021-00658-6. IF: 24.427
Molecular Russian dolls (matryoshkas) have proven useful for testing the limits of preparative supramolecular chemistry but applications of these architectures to problems in other fields are elusive. Here we report a three-shell, matryoshka-like complex—in which C60 sits inside a cycloparaphenylene nanohoop, which in turn is encapsulated inside a self-assembled nanocapsule—that can be used to address a long-standing challenge in fullerene chemistry, namely the selective formation of a particular fullerene bis-adduct. Spectroscopic evidence indicates that the ternary complex is sufficiently stable in solution for the two outer shells to affect the addition chemistry of the fullerene guest. When the complex is subjected to Bingel cyclopropanation conditions, the exclusive formation of a single trans-3 fullerene bis-adduct was observed in a reaction that typically yields more than a dozen products. The selectivity facilitated by this matryoshka-like approach appears to be a general phenomenon and could be useful for applications where regioisomerically pure C60 bis-adducts have been shown to have superior properties compared with isomer mixtures. [Figure not available: see fulltext.] © 2021, The Author(s), under exclusive licence to Springer Nature Limited.
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Assembly of Colloidal Clusters Driven by the Polyhedral Shape of Metal-Organic Framework Particles
Liu Y., Wang J., Imaz I., Maspoch D. Journal of the American Chemical Society; 143 (33): 12943 - 12947. 2021. 10.1021/jacs.1c05363. IF: 15.419
Control of the assembly of colloidal particles into discrete or higher-dimensional architectures is important for the design of myriad materials, including plasmonic sensing systems and photonic crystals. Here, we report a new approach that uses the polyhedral shape of metal-organic-framework (MOF) particles to direct the assembly of colloidal clusters. This approach is based on controlling the attachment of a single spherical polystyrene particle on each face of a polyhedral particle via colloidal fusion synthesis, so that the polyhedral shape defines the final coordination number, which is equal to the number of faces, and geometry of the assembled colloidal cluster. As a proof of concept, we assembled six-coordinated (6-c) octahedral and 8-c cubic clusters using cubic ZIF-8 and octahedral UiO-66 core particles. Moreover, we extended this approach to synthesize a highly coordinated 12-c cuboctahedral cluster from a rhombic dodecahedral ZIF-8 particle. We anticipate that the synthesized colloidal clusters could be further evolved into spherical core-shell MOF@polystyrene particles under conditions that promote a higher fusion degree, thus expanding the methods available for the synthesis of MOF-polymer composites. ©
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Buttermilk as encapsulating agent: Effect of ultra-high-pressure homogenization on chia oil-in-water liquid emulsion formulations for spray drying
Aghababaei F., Cano-Sarabia M., Trujillo A.J., Quevedo J.M., Ferragut V. Foods; 10 (5, 1059) 2021. 10.3390/foods10051059. IF: 4.350
Functional foods are highly demanded by consumers. Omega-3 rich oil and commercial buttermilk (BM), as functional components, used in combination to produce emulsions for further drying may facilitate the incorporation to foods. Ultra-high-pressure homogenization (UHPH) has a great potential for technological and nutritional aspects in emulsions production. The present study aimed to examine the potential improvement of UHPH technology in producing buttermilk-stabilized omega-3 rich emulsions (BME) for further drying, compared with conventional homogenization. Oil-in-water emulsions formulated with 10% chia: sunflower oil (50:50); 30% maltodextrin and 4 to 7% buttermilk were obtained by using conventional homogenization at 30 MPa and UHPH at 100 and 200 MPa. Particle size analysis, rheological evaluation, colloidal stability, zeta-potential measurement, and microstructure observations were performed in the BME. Subsequent spray drying of emulsions were made. As preliminary approximation for evaluating differences in the homogenization technology applied, encapsulation efficiency and morphological characteristics of on spray-dried emulsions (SDE) containing 21.3 to 22.7% oil content (dry basis) were selected. This study addresses the improvement in stability of BME treated by UHPH when compared to conventional homogenization and the beneficial consequences in encapsulation efficiency and morphology of SDE. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
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Elucidating pore chemistry within metal-organic frameworksviasingle crystal X-ray diffraction; from fundamental understanding to application
Albalad J., Sumby C.J., Maspoch D., Doonan C.J. CrystEngComm; 23 (11): 2185 - 2195. 2021. 10.1039/d1ce00067e. IF: 3.545
Metal-organic frameworks (MOFs) have made inroads in diverse chemical sectors due to the essentially limitless combination of building units and the ability to post-synthetically modify their pore chemistry at the molecular level. The crystalline nature of MOFs permits the use of single crystal X-ray diffraction (SCXRD) to obtain crystallographic snapshots of these transformations, providing invaluable information into the unorthodox chemistry that MOFs can potentially offer. This highlight article aims to provide the reader with the most recent milestones in the use of SCXRD as a vanguard technique to connect molecular-level pore engineering of MOFs with new application fields hitherto unexplored. © The Royal Society of Chemistry 2021.
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Engineering covalent organic frameworks in the modulation of photocatalytic degradation of pollutants under visible light conditions
Jiménez-Almarza A., López-Magano A., Cano R., Ortín-Rubio B., Díaz-García D., Gomez-Ruiz S., Imaz I., Maspoch D., Mas-Ballesté R., Alemán J. Materials Today Chemistry; 22 (100548) 2021. 10.1016/j.mtchem.2021.100548. IF: 8.301
Mixtures of triphenylamine (TPA) and phenyl phenothiazine (PTH) fragments have been incorporated into a series of extended polyimine structures that have been applied in the photodegradation of pollutants of different nature under visible light irradiation. Results obtained revealed that materials containing PTH as the sole photoactive unit resulted in the most active photocatalytic material in the degradation of polybrominated diphenyl ether-1 and Sudan Red III. In contrast, the covalent organic framework containing only TPA acted as the best photocatalyst for the degradation of Methylene Blue. These different trends are related to the versatility of PTH moiety to trigger both photoredox and energy transfer processes, while TPA is only an effective energy transfer catalyst. © 2021 Elsevier Ltd
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Heterogeneous catalysts with programmable topologies generated by reticulation of organocatalysts into metal-organic frameworks: The case of squaramide
Broto-Ribas A., Vignatti C., Jimenez-Almarza A., Luis-Barrera J., Dolatkhah Z., Gándara F., Imaz I., Mas-Ballesté R., Alemán J., Maspoch D. Nano Research; 14 (2): 458 - 465. 2021. 10.1007/s12274-020-2779-8. IF: 8.897
A well-established strategy to synthesize heterogeneous, metal-organic framework (MOF) catalysts that exhibit nanoconfinement effects, and specific pores with highly-localized catalytic sites, is to use organic linkers containing organocatalytic centers. Here, we report that by combining this linker approach with reticular chemistry, and exploiting three-dimensioanl (3D) MOF-structural data from the Cambridge Structural Database, we have designed four heterogeneous MOF-based catalysts for standard organic transformations. These programmable MOFs are isoreticular versions of pcu IRMOF-16, fcu UiO-68 and pillared-pcu SNU-8X, the three most common topologies of MOFs built from the organic linker p,p’-terphenyldicarboxylic acid (tpdc). To synthesize the four squaramide-based MOFs, we designed and synthesized a linker, 4,4’-((3,4‐dioxocyclobut‐1‐ene‐1,2‐diyl)bis(azanedyil))dibenzoic acid (Sq_tpdc), which is identical in directionality and length to tpdc but which contains organocatalytic squaramide centers. Squaramides were chosen because their immobilization into a framework enhances its reactivity and stability while avoiding any self-quenching phenomena. Therefore, the four MOFs share the same organocatalytic squaramide moiety, but confine it within distinct pore environments. We then evaluated these MOFs as heterogeneous H-bonding catalysts in organic transformations: a Friedel-Crafts alkylation and an epoxide ring-opening. Some of them exhibited good performance in both reactions but all showed distinct catalytic profiles that reflect their structural differences. [Figure not available: see fulltext.]. © 2020, Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature.
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Heterogeneous Microscopic Dynamics of Intruded Water in a Superhydrophobic Nanoconfinement: Neutron Scattering and Molecular Modeling
Wolanin J., Michel L., Tabacchioni D., Zanotti J.M., Peters J., Imaz I., Coasne B., Plazanet M., Picard C. Journal of Physical Chemistry B; 125 (36): 10392 - 10399. 2021. 10.1021/acs.jpcb.1c06791. IF: 2.991
With their strong confining porosity and versatile surface chemistry, zeolitic imidazolate frameworks—including the prototypical ZIF-8—display exceptional properties for various applications. In particular, the forced intrusion of water at high pressure (∼25 MPa) into ZIF-8 nanopores is of interest for energy storage. Such a system reveals also ideal to study experimentally water dynamics and thermodynamics in an ultrahydrophobic confinement. Here, we report on neutron scattering experiments to probe the molecular dynamics of water within ZIF-8 nanopores under high pressure up to 38 MPa. In addition to an overall confinement-induced slowing down, we provide evidence for strong dynamical heterogeneities with different underlying molecular dynamics. Using complementary molecular simulations, these heterogeneities are found to correspond to different microscopic mechanisms inherent to vicinal molecules located in strongly adsorbing sites (ligands) and other molecules nanoconfined in the cavity center. These findings unveil a complex microscopic dynamics, which results from the combination of surface residence times and exchanges between the cavity surface and center. © 2021 American Chemical Society
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Macroscopic Ultralight Aerogel Monoliths of Imine-based Covalent Organic Frameworks
Martín-Illán J.Á., Rodríguez-San-Miguel D., Castillo O., Beobide G., Perez-Carvajal J., Imaz I., Maspoch D., Zamora F. Angewandte Chemie - International Edition; 60 (25): 13969 - 13977. 2021. 10.1002/anie.202100881. IF: 15.336
The use of covalent organic frameworks (COFs) in practical applications demands shaping them into macroscopic objects, which remains challenging. Herein, we report a simple three-step method to produce COF aerogels, based on sol-gel transition, solvent-exchange, and supercritical CO2 drying, in which 2D imine-based COF sheets link together to form hierarchical porous structures. The resultant COF aerogel monoliths have extremely low densities (ca. 0.02 g cm−3), high porosity (total porosity values of ca. 99 %), and mechanically behave as elastic materials under a moderate strain (<25–35 %) but become plastic under greater strain. Moreover, these COF aerogels maintain the micro- and meso-porosity of their constituent COFs, and show excellent absorption capacity (e.g. toluene uptake: 32 g g−1), with high removal efficiency (ca. 99 %). The same three-step method can be used to create functional composites of these COF aerogels with nanomaterials. © 2021 Wiley-VCH GmbH
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Millimeter-Shaped Metal-Organic Framework/Inorganic Nanoparticle Composite as a New Adsorbent for Home Water-Purification Filters
Boix G., Han X., Imaz I., Maspoch D. ACS Applied Materials and Interfaces; 13 (15): 17835 - 17843. 2021. 10.1021/acsami.1c02940. IF: 9.229
Heavy-metal contamination of water is a global problem with an especially severe impact in countries with old or poorly maintained infrastructure for potable water. An increasingly popular solution for ensuring clean and safe drinking water in homes is the use of adsorption-based water filters, given their affordability, efficacy, and simplicity. Herein, we report the preparation and functional validation of a new adsorbent for home water filters, based on our metal-organic framework (MOF) composite containing UiO-66 and cerium(IV) oxide (CeO2) nanoparticles. We began by preparing CeO2@UiO-66 microbeads and then encapsulating them in porous polyethersulfone (PES) granules to obtain millimeter-scale CeO2@UiO-66@PES granules. Next, we validated these granules as an adsorbent for the removal of metals from water by substituting them for the standard adsorbent (ion-exchange resin spheres) inside a commercially available water pitcher from Brita. We assessed their performance according to the American National Standards Institute (ANSI) guideline 53-2019, "Drinking Water Treatment Units - Health Effects Standard". Remarkably, a pitcher loaded with a combination of our CeO2@UiO-66@PES granules and activated carbon at standard ratios met the target reduction thresholds set by NSF/ANSI 53-2019 for all the metals tested: As(III), As(V), Cd(II), Cr(III), Cr(VI), Cu(II), Hg(II), and Pb(II). Throughout the test, the modified pitcher proved to be robust and stable. We are confident that our findings will bring MOF-based adsorbents one step closer to real-world use. © 2021 American Chemical Society.
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Mouthwashes with CPC Reduce the Infectivity of SARS-CoV-2 Variants In Vitro
Muñoz-Basagoiti J., Perez-Zsolt D., León R., Blanc V., Raïch-Regué D., Cano-Sarabia M., Trinité B., Pradenas E., Blanco J., Gispert J., Clotet B., Izquierdo-Useros N. Journal of Dental Research; 100 (11): 1265 - 1272. 2021. 10.1177/00220345211029269. IF: 6.116
Oral mouthwashes decrease the infectivity of several respiratory viruses including SARS-CoV-2. However, the precise agents with antiviral activity in these oral rinses and their exact mechanism of action remain unknown. Here we show that cetylpyridinium chloride (CPC), a quaternary ammonium compound in many oral mouthwashes, reduces SARS-CoV-2 infectivity by inhibiting the viral fusion step with target cells after disrupting the integrity of the viral envelope. We also found that CPC-containing mouth rinses decreased more than a thousand times the infectivity of SARS-CoV-2 in vitro, while the corresponding vehicles had no effect. This activity was effective for different SARS-CoV-2 variants, including the B.1.1.7 or Alpha variant originally identified in United Kingdom, and in the presence of sterilized saliva. CPC-containing mouth rinses could therefore represent a cost-effective measure to reduce SARS-CoV-2 infectivity in saliva, aiding to reduce viral transmission from infected individuals regardless of the variants they are infected with. © International & American Associations for Dental Research 2021.
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Perspectives for polychlorinated trityl radicals
Ratera I., Vidal-Gancedo J., Maspoch D., Bromley S.T., Crivillers N., Mas-Torrent M. Journal of Materials Chemistry C; 9 (33): 10610 - 10623. 2021. 10.1039/d1tc02196f. IF: 7.393
An organic free radical is a molecule with one or more unpaired electrons. Although most free radicals are highly reactive, chemists have developed a few families of so-called persistent organic radicals with high kinetic stabilities. Polychlorinated trityl radicals, also known as polychlorotriphenylmethyl (PTM) radicals, are particularly chemically stable due to the high steric hindrance provided by the chlorine atoms in ortho positions which protect their single unpaired electron localised on the central carbon atom. In addition to their inherent magnetic spin due to the unpaired electron, PTMs exhibit other appealing properties such as a rich electrochemistry and characteristic optical properties (absorption and emission). Moreover, it has been shown that these properties can be tuned through the preparation of a large library of PTM-based derivatives. Here, we review recent developments employing PTM radicals, which include their implementation in molecular electronic junctions/switches, as building blocks for the preparation of magnetic networks and opto-electronic devices/materials and their exploitation in bio-applications. © 2021 The Royal Society of Chemistry.
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Photoredox Heterobimetallic Dual Catalysis Using Engineered Covalent Organic Frameworks
López-Magano A., Ortín-Rubio B., Imaz I., Maspoch D., Alemán J., Mas-Ballesté R. ACS Catalysis; 11 (19): 12344 - 12354. 2021. 10.1021/acscatal.1c03634. IF: 13.084
The functionalization of an imine-based layered covalent organic framework (COF), containing phenanthroline units as ligands, has allowed the obtention of a heterobimetallated material. Photoactive Ir and Ni fragments were immobilized within the porous structure of the COF, enabling heterogeneous light-mediated Csp3-Csp2cross-couplings. As radical precursors, potassium benzyl- and alkoxy-trifluoroborates, organic silicates, and proline derivatives were employed, which brings out the good versatility ofIr,Ni@Phen-COF. Moreover, in all the studied cases, an enhanced activity and stability have been observed in comparison with analogous homogenous systems. © 2021 American Chemical Society
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Steric Hindrance in Metal Coordination Drives the Separation of Pyridine Regioisomers Using Rhodium(II)-Based Metal–Organic Polyhedra
Hernández-López L., Martínez-Esaín J., Carné-Sánchez A., Grancha T., Faraudo J., Maspoch D. Angewandte Chemie - International Edition; 60 (20): 11406 - 11413. 2021. 10.1002/anie.202100091. IF: 15.336
The physicochemical similarity of isomers makes their chemical separation through conventional techniques energy intensive. Herein, we report that, instead of using traditional encapsulation-driven processes, steric hindrance in metal coordination on the outer surface of RhII-based metal–organic polyhedra (Rh-MOPs) can be used to separate pyridine-based regioisomers via liquid–liquid extraction. Through molecular dynamics simulations and wet experiments, we discovered that the capacity of pyridines to coordinatively bind to Rh-MOPs is determined by the positions of the pyridine substituents relative to the pyridine nitrogen and is influenced by steric hindrance. Thus, we exploited the differential solubility of bound and non-bound pyridine regioisomers to engineer liquid–liquid self-sorting systems. As a proof of concept, we separated four different equimolecular mixtures of regioisomers, including a mixture of the industrially relevant compounds 2-chloropyridine and 3-chloropyridine, isolating highly pure compounds in all cases. © 2021 Wiley-VCH GmbH
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Synthesis of Polycarboxylate Rhodium(II) Metal–Organic Polyhedra (MOPs) and their use as Building Blocks for Highly Connected Metal–Organic Frameworks (MOFs)
Grancha T., Carné-Sánchez A., Zarekarizi F., Hernández-López L., Albalad J., Khobotov A., Guillerm V., Morsali A., Juanhuix J., Gándara F., Imaz I., Maspoch D. Angewandte Chemie - International Edition; 60 (11): 5729 - 5733. 2021. 10.1002/anie.202013839. IF: 15.336
Use of preformed metal-organic polyhedra (MOPs) as supermolecular building blocks (SBBs) for the synthesis of metal-organic frameworks (MOFs) remains underexplored due to lack of robust functionalized MOPs. Herein we report the use of polycarboxylate cuboctahedral RhII-MOPs for constructing highly-connected MOFs. Cuboctahedral MOPs were functionalized with carboxylic acid groups on their 12 vertices or 24 edges through coordinative or covalent post-synthetic routes, respectively. We then used each isolated polycarboxylate RhII-MOP as 12-c cuboctahedral or 24-c rhombicuboctahedral SBBs that, upon linkage with metallic secondary building units (SBUs), afford bimetallic highly-connected MOFs. The assembly of a pre-synthesized 12-c SBB with a 4-c paddle-wheel SBU, and a 24-c SBB with a 3-c triangular CuII SBU gave rise to bimetallic MOFs having ftw (4,12)-c or rht (3,24)-c topologies, respectively. © 2020 Wiley-VCH GmbH
