1,721,019 research outputs found
Re-thinking organic synthesis: Mechanochemistry as a greener approach
No full textThe increasing advances in mechanochemistry have opened new possibilities to develop organic processes in a more sustainable way. In this contribution, recent progress in this area has been described, going from laboratory scale protocols to industrial applications. Moreover, innovations in mechanochemical procedures and in-situ characterization analyses have been also discussed. Envisioning scale-up applications, several technologies such as twin-screw extrusion and high-throughput reaction platforms, able to combine continuous-flow mechanochemical and thermal conditions, have been investigated and developed. It is worth remarking that mechanochemistry is a highly promising approach with a lot of potentialities still to be unraveled
Editorial overview: Editorial green and sustainable nanotechnology
No full textIn summary, this Special Issue provides in-depth information about the opportunities of biomass for nanomaterials design and synthesis of valuable products, considering the sustainability of the process in each case. We believe this collection will motivate many researchers toward the development of a greener and more sustainable nanotechnology
Versatile functionalized mesoporous Zr/SBA-15 for catalytic transfer hydrogenation and oxidation reactions
No full textThrough this work, a family of sulfonamide functionalized mesoporous materials as sustainable heterogeneous catalysts has been successfully synthesized by employing sulfaguanidine, sulfathiazole, and sulfadiazine. The samples were fully characterized using a multitechnique approach. Such materials have proved to be highly versatile and catalytically active in both the advances in the hydrogenation of Levulinic acid through heterogeneous catalytic transfer hydrogenation (CTH) and oxidation reactions with a strong emphasis on discussing morphology and structure of versatile catalysts, plausible mechanism, and performance of the catalysts for biomass valorization of renewable feedstock. In particular, the prepared catalytic systems were tested in levulinic acid transformation into γ-Valerolactone, achieving a maximum conversion of 99% and a selectivity of 90% for the sulfaguanidine modified sample. The three nanocatalysts displayed good stability over four reuse cycles, and by considering the results of a hot filtration test, it is confirmed that the nature of the catalysis is heterogeneous as acid-base pairs and functionalized groups on catalytic activation of C–H and C[dbnd]O bonds for transfer hydrogenation of levulinic acid. Moreover, such samples also showed remarkable results in the oxidation of benzyl alcohol towards benzaldehyde, with conversion and selectivity values of 95% and 97%, respectively. The obtained catalytic results are highly promising for biomass upgrading processes, looking forward to a more sustainable future
Waste-derived Materials: Opportunities in Photocatalysis
No full textWaste-derived materials have been gaining increased attention in recent years due to their great potential and environmentally friendly nature. Several contributions in the literature have covered the advances achieved so far in this area. Nonetheless, to the best of our knowledge, no review has been dedicated specifically to waste-derived or templated photocatalytic materials. Both photocatalysis and (bio)waste-inspired design yield materials of a remarkably green nature. Therefore, the partnership between them may open promising possibilities for both waste valorization and photocatalytic processes, which in turn will lead to sustainable development globally, with the potential for full utilization of renewable energy sources such as biomass and sunlight. Several photocatalytic waste-derived materials, synthetic procedures, and applications will be described throughout this work, including waste-derived/templated TiO2, ZnO, and metal sulfide materials. Special attention will be given to biomass-inspired carbonaceous materials, including carbon quantum dots and graphitic carbon nitride (g-C3N4)
Alternative Perovskites for Photovoltaics
No full textThe discovery of unique optoelectronic properties of 3D ABX3 perovskites has produced a great impact on the field of photovoltaics. In the initial years after the breakthrough, interest has focused on a limited number of 3D ABX3 perovskite materials, including the archetypal CH3NH3PbI3 and its counterparts. Undoubtedly, the main limitation of perovskite devices is their low stability due the fast degradation of the perovskite layer; however, the high toxicity of Pb also poses a concern. Herein, the recent increasing number of articles reporting the theoretical modeling, synthesis, optoelectronic characterization, and implementation of alternative perovskite materials in solar devices is summarized. The extensive variety of perovskite derivatives is classified according to the material dimensionality and the crystal structure. The particular strengths and weaknesses for each novel material are discussed, and the device performance and potential stability enhancements are also highlighted
Unlocking the Potential of Liquid Multiphase Systems for Metal‐Catalysed Reactions
No full textLiquid multiphase systems (MPS) have gained attention in recent years due to their versatility for catalytic processes. This review article presents a critical discussion of the most recent advances on the utilization of MPS in both homogeneous and heterogeneous metal-catalysed reactions. Pros and cons of some exemplificative multiphase configurations are highlighted and compared to conventional methods in single liquid solvents. The application of MPS for the implementation of strategies for the upgrading of biobased molecules is also examined with emphasis on process intensification and sustainability including the catalyst/products separation and the in-situ recycle and reuse of the metal catalysts. These aspects are analyzed with a view on expanding MPS applications and whenever possible, explore scale-up opportunities.The potential of liquid-liquid multiphase systems in homogeneous and heterogeneous catalysis has been described through examples in recent literature, showcasing advantages, current challenges, and potential impacts on sustainability and biomass valorization strategies. imag
Recent advances in catalytic hydrogenation of furfural
No full textFurfural has been considered as one of the most promising platform molecules directly derived from biomass. The hydrogenation of furfural is one of the most versatile reactions to upgrade furanic components to biofuels. For instance, it can lead to plenty of downstream products, such as (tetrahydro)furfuryl alcohol, 2-methyl(tetrahydro)furan, lactones, levulinates, cyclopentanone(l), or diols, etc. The aim of this review is to discuss recent advances in the catalytic hydrogenation of furfural towards (tetrahydro)furfuryl alcohol and 2-methyl(tetrahydro)furan in terms of different non-noble metal and noble metal catalytic systems. Reaction mechanisms that are related to the different catalytic materials and reaction conditions are properly discussed. Selective hydrogenation of furfural could be modified not only by varying the types of catalyst (nature of metal, support, and preparation method) and reaction conditions, but also by altering the reaction regime, namely from batch to continuous flow. In any case, furfural catalytic hydrogenation is an open research line, which represents an attractive option for biomass valorization towards valuable chemicals and fuels
Simplifying Levulinic Acid Conversion Towards a Sustainable Biomass Valorisation
No full textThe demand for sustainable and robust catalysts for the valorisation of biomass is strictly related to the more and more pressing request to not only replace petroleum fuels with eco-friendly alternatives, but also to produce added value chemicals. In this context, the use of noble metals is not practically and economically sustainable and more abundant and stable alternatives are needed. In this contribution we have prepared and tested metal transition based catalysts (namely Ni3N and Ni nanoparticles) for the hydroconversion of levulinic acid (LA) as a model reaction. LA is useful also to produce valuable N-substituted pyrrolidones. Nanoparticles were prepared via a greener synthesis, using urea and metal salts, and have an average diameter of ∼30 nm (as ascertained by XRD and TEM studies). The main product of the levulinic acid hydroconversion was 1-ethyl-5-methylpyrrolidin-2-one. While this product was always the preferred one when Ni was used, Ni3N favoured the formation of the main product only in a shorter reaction time (below 1 h) with very high selectivity (up to 55% conversion), while a secondary product was formed in a longer time. The stability of the catalysts was also tested. To the best of our knowledge this is the first time that such a reaction is tested using transition metals and metal nitrides, with very promising results
Continuous flow synthesis of high valuable N-heterocycles via catalytic conversion of levulinic acid
No full textGraphitic carbon nitride (g-C3N4) was successfully functionalized with a low platinum loading to give rise to an effective and stable catalytic material. The synthesized g-C3N4/Pt was fully characterized by XRD, N2 physisorption, XPS, SEM-Mapping, and TEM techniques. Remarkably, XPS analysis revealed that Pt was in a dominant metallic state. In addition, XPS together with XRD and N2 physisorption measurements indicated that the g-C3N4 preserves its native structure after the platinum deposition process. g-C3N4/Pt was applied to the catalytic conversion of levulinic acid to N-heterocycles under continuous flow conditions. Reaction parameters (temperature, pressure, and concentration of levulinic acid) were studied using 3 levels for each parameter, and the best conditions were employed for the analysis of the catalyst's stability. The catalytic system displayed high selectivity to 1-ethyl-5-methylpyrrolidin-2-one and outstanding stability after 3 h of reaction
Mechanochemical synthesis of one-dimensional (1D) hybrid perovskites incorporating polycyclic aromatic spacers: Highly fluorescent cation-based materials
No full textThree polycyclic aromatic cations, 2-ammonium fluorene (AF), 2-ammonium anthracene (AA) and 2,7-diammonium fluorene (DAF) are successfully assembled with inorganic PbBr6 octahedra to synthesize (AF/AA)2PbBr4 and (DAF)PbBr4 one-dimensional (1D) hybrid perovskites. The synthesis of the perovskites is performed via an environmentally-friendly mechanochemical approach involving a solid-state solventless reaction. The analysis of the X-ray powder diffraction (XRD) data revealed that the crystal structure of these materials consisted of quasi-linear wires of PbBr42- separated by polycyclic cations with alternating positions of NH3+ groups. DFT calculations have shown a remarkable contribution of the orbitals of 2-ammonium fluorene to both the valence band maximum (VBM) and conduction band minimum (CBM) of the (AF)2PbBr4 structure. Moreover, the same hybrid materials were effectively prepared as thin films by using the spin-coating method from a solution containing the precursors. Although these hybrid perovskites are not intrinsically emissive, the strong fluorescence signal from the organic cation is preserved
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