Palladium Supported on Porous Chitosan-Graphene Oxide Aerogels as Highly Efficient Catalysts for Hydrogen Generation from Formate

[EN] Adsorption of Pd(NH3)(4)(2+) in preformed chitosan-graphene oxide (CS-GO) beads and their subsequent reduction with NaBH4 afford well-dispersed, high dispersion (similar to 21%) of uniformly sized Pd nanoparticles (similar to 1.7 nm). The resulting Pd/CS-GO exhibits interesting catalytic activity for hydrogen generation by ammonium formate decomposition. The optimal GO proportion of 7 wt% allows reaching, at 60 degrees C, a turnover frequency above 2200 h(-1)-being outstanding among the highest values reported for this process to date. Interestingly, no formation of CO or CH4 was detected. The catalyst did not leach, although it underwent gradual deactivation, probably caused by the increase in the Pd average size that became over 3 nm after three uses. Our results are relevant in the context of efficient on-board hydrogen generation from liquid organic hydrogen carriers in transportation.This research was funded by the Spanish Ministry of Science, Innovation and Universities (Grant RTI2018-098237-B-C21 and Severo Ochoa). A.P. also thanks the Spanish Ministry of Science and Education a research associate Ramon y Cajal contract. A.A. thanks UEMF for scholarship.Anouar, A.; Katir, N.; El Kadib, A.; Primo Arnau, AM.; García Gómez, H. (2019). Palladium Supported on Porous Chitosan-Graphene Oxide Aerogels as Highly Efficient Catalysts for Hydrogen Generation from Formate. Molecules. 24(18):1-13. https://doi.org/10.3390/molecules24183290S113241

Remarkable Activity of 002 Facet of Ruthenium Nanoparticles Grown on Graphene Films on the Photocatalytic CO2 Methanation

[EN] In the context of diminishing atmospheric CO2 emissions, there is an urgent need to develop processes that can be carried out at a scale commensurate with appropriate CO2 volumes. One possible reaction is the transformation of CO2 to methane (Sabatier reaction). Due to its chemical stability, catalytic CO2 hydrogenation to methane is carried out at temperatures of 450 degrees C or higher and pressures above 5 bars, thus, requiring a significant energy input. One alternative possibility to conventional thermal catalysis is the use of solar light as the primary energy, performing the photocatalytic CO2 hydrogenation. In this broad context, the present study shows the photocatalytic activity of nanometric films of oriented Ru nanoparticles (NPs) strongly grafted on defective graphene. These graphene films (thinner than 20 nm) containing Ru NPs nanoplatelets (less than 2 nanomol(Ru)/cm(2)) are among the most active photocatalysts ever prepared for CO2 hydrogenation and operate through photoinduced charge separationSupport by the Ministerio de Ciencia e Innovacion (Severo Ochoa and RTI2018-098237-B-C21) and Generalitat Valenciana (Prometeo 2017/083) was acknowledged. Thanks are due to Galicia Supercomputing Center. A.A. thanks UEMF (Euromed Unniversity Fes) and UPV for an Erasmus+ 2019-1-ES01-KA107-062073 Scholarship. A.P. thanks the Spanish Ministry for a Ramon y Cajal research associate contract.Anouar, A.; García-Aboal, R.; Atienzar Corvillo, PE.; Franconetti, A.; Katir, N.; El Kadib, A.; Primo Arnau, AM.... (2022). Remarkable Activity of 002 Facet of Ruthenium Nanoparticles Grown on Graphene Films on the Photocatalytic CO2 Methanation. Advanced Sustainable Systems. 6(5):1-10. https://doi.org/10.1002/adsu.2021004871106

Organophosphonate bridged anatase mesocrystals: low temperature crystallization, thermal growth and hydrogen photo-evolution

The sol-gel co-condensation of organo-phosphonates to titanium alkoxides enables access to novel organic-inorganic hybrids based on phosphonate-bridged titanium dioxide. In this contribution, we bring new perspectives to the long established sol-gel mineralization of titanium alkoxide species, by harnessing the virtues of the well-designed phosphonate-terminated phosphorus dendrimers as reactive amphiphilic nanoreactor, confined medium and cross-linked template to generate discrete crystalline anatase nanoparticles at low temperature (T = 60 degrees C). An accurate investigation on several parameters (dendrimer generation, dendrimer-to-titanium alkoxide ratio, precursor reactivity, temperature, solvent nature, salt effect) allows a correlation between the network condensation, the opening porous framework and the crystalline phase formation. The evolution of the dendrimer skeleton upon heat treatment has been deeply monitored by means of P-31 NMR, XPS and Raman spectroscopy. Increasing the heteroatom content within a titania network provides the driving force for enhancing their photocatalytic water splitting ability for hydrogen production.Brahmi, Y.; Katir, N.; Macia Agullo, JA.; Primo Arnau, AM.; Bousmina, M.; Majoral, J.; García Gómez, H.... (2015). Organophosphonate bridged anatase mesocrystals: low temperature crystallization, thermal growth and hydrogen photo-evolution. Dalton Transactions. 44(35):15544-15556. doi:10.1039/c5dt02367jS1554415556443

Esters méthyliques d'acides gras fonctionnalisés (B, Si, Ge, P) : Polyesters métallés - Nanoparticules de germanium

This work concerns the functionalization of fatty acid methyl esters (FAME) with the intention of promoting Moroccan sea resources and particularly fish oils. The first chapter describes the hydroboration reactions of FAME. The determination of the selectivity was established basing on the oxidized corresponding derivatives. In the second chapter, hydrometallation (Si, Ge) reactions were described, transition-metal catalysis was used starting from linear and cyclic siloxanes or radical initiation with arylgermanes. A series of silylated and germylated di- and poly-esters with variable chain lengths and organometallic groups in different positions was prepared and characterized by classical tools such as NMR, mass spectrometry. The third chapter refers to the phosphorylation of FAME. Two different routes were investigated: a metallation reaction with lithium phosphide and a base-induced dehydrohalide coupling reaction leading to C-phosphorylated and O-phosphorylated derivatives containing one or two FAME. In the last chapters, were developed some applications of functional FAME in two different areas: polymers and nanoparticles. The fourth chapter concerns the preparation of polymers by direct transesterification between silylated and germylated diesters or diols and polydiols or PBT respectively. These new polyesters were perfectly characterized and presented very good thermal stability. They were also used as soft block in polycondensation with PBT giving stable copolymers. The last chapter evidenced a promising route to germanium nanoparticles by thermal decomposition in solution of N-chelated germanium(II) species. Moreover, these mild conditions offer the possibility to control the size and the morphology of the obtained nano-objets.Ce travail concerne la fonctionnalisation des esters méthyliques d'acides gras (EMAG) dans le but de valoriser les ressources halieutiques marocaines, en particulier les huiles de poisson dont ils sont les principaux constituants. Pour cela, des réactions d'hydroboration, d'hydrosilylation, d'hydrogermylation et de phosphorylation ont été réalisées dans les premier, deuxième et troisième chapitres et ont permis d'accéder à une grande variété de composés présentant des motifs EMAG diversement substitués. Dans les deux derniers chapitres, nous avons développé des applications de ces dérivés. Ainsi, des polyesters et des copolymères renfermant un élément du groupe 14 et un motif de type EMAG ont été préparés et caractérisés. Parallèlement, la décomposition thermique en solution d'aminogermylènes nous a permis d'accéder à des nanoparticules de germanium

Esters méthyliques d'acides gras fonctionnalisés (B, Si, Ge, P) (Polyesters métallés, nanoparticules de germanium)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Phosphorylated micro- vs. Nano-cellulose: a comparative study on their surface functionalisation, growth of titanium-oxo-phosphate clusters and removal of chemical pollutants

International audienceControlled cellulose disassembly affords many variants including amorphous micro-sized cellulose crystals (MCC) and cellulose nano-sized crystals (CNC), which have emerged recently as green and sustainable nanomaterials. Unfortunately, their lower reactivity and thermal and chemical instability constitute an impediment for multifaceted nanoscience and nanotechnology usage. Herein, MCC and CNC are functionalised using two phosphorus derivatives (phosphoryl chloride and hexachlorocyclotriphosphazene), under acid-free, urea-free and corrosive-free, gentle experimental conditions. Notably, CNC can accommodate more phosphorus species compared to MCC, with the bulky phosphazene precursor being less reactive in both cases. In contrast, CNC is less prone to post-grafting titanium alkoxide species compared to MCC. Alternatively, phosphorylation circumvents this drawback and enhanced post-grafting reactivity was observed for P-MCC and P-CNC modified cellulose. The presence of phosphorus fragments provides a way of anchoring ultrastable metal oxide clusters on the nanofibrillar surface through metal–phosphonate (P–O–Ti) bridges. Direct condensation of soluble phosphorus reagents with metal alkoxide bearing acetylacetonate fragments constitutes another alternative to grow a substantial amount of metal oxide clusters on both MCC and CNC. The beneficial effect of phosphorus incorporation is convincingly illustrated by their efficiency to scavenge representative anionic and cationic dye pollutants compared to native, non-modified cellulose and its carboxymethylcellulose analogues

Germylenes and stannylenes with chelating anilido-imine ligands- syntheses, structures, and reactivity

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Aldehyde-conjugated chitosan-graphene oxide glucodynamers: ternary cooperative assembly and controlled chemical release

Simultaneous condensation of aromatic aldehydes (ArxCHO; x =1–4) on chitosan biopolymer (CS)affords, after water-evaporation, structurally-conjugated aryl-functionalized CS-Arx-ffilms. Similarly, cooperative assembly of two-dimensional nanometric graphene oxide (GO), aromatic aldehyde and chitosan provides transparent, flexible and crack-free aldehyde-functionalized, ternary-reinforced CS-Arx-GO-f nanocomposite films. Homogenous films were obtained using ortho-hydroxybenzaldehyde Ar1 while the para-hydroxybenzaldehyde Ar4 was prone to packing inside. Textural and mechanical properties were investigated and expectedly, sig- nificant improvement was found for CS-Ar1-GO-f because of the great dispersion of the aromatic and the pre- sence of the filler. The sensitivity of unsaturated C]N imine bond to hydrolysis was explored for triggering controlled release of aromatics from the as-prepared films. All of them were found to induce a time-dependent aromatic release. It has been moreover observed that the release was significantly delayed in CS-Arx-GO-f compared to CS-Arx-f, a fact attributed to the interplay of the ring with the basal and edges of graphene oxide, through π-π stacking and additional hydrogen bonding interactions. This finding shows that beyond the con- ventional wisdom using fillers for improving thermal and mechanical properties, the tiny carbon sheets can act as a regulator for aldehyde release, thereby providing a way for more controlled chemical delivery from confined nanocomposites

Polysaccharide templated biomimetic growth of hierarchically porous metal-organic frameworks

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