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International audience; A green method for the production of cobalt/(TEMPO-Cellulose) aerogel heterogeneous catalyst was developed. The preparation implied the reduction of CoSO4 by NaBH4 in TEMPO-Cellulose water dispersion in ambient conditions. The formation of Cobalt nanoparticles is due to the presence of “TEMPO-Cell” which screens the Co2+ ions and prevents their combination with boron. SEM, XRD, EDX, FTIR, TEM and XPS were used to analyze the structure of the catalyst and showed that metallic cobalt particles have nanometric size and are well dispersed in the aerogel. The catalyst showed excellent activity for model reactions such as the reduction of 4-nitroaniline, 4-nitrophenol and 2-nitrophenol in water, in the presence of NaBH4. The reaction kinetic was studied by UV–visible spectroscopy, which showed that this catalyst is efficient to achieve 100 % reduction with high reaction rate and turnover frequency. The aerogel catalyst was reused more than ten times without significant loss of its catalytic activity.

Foam products are one of the largest markets for polyurethane (PU) and are heavily used in many sectors. However, current PU formulations use highly toxic and environmentally unfriendly production processes. Meanwhile, the increasing environmental concerns and regulations are intensifying the research into green and non-toxic products. In this study, we synthesized flexible polyurethane foam (PUF) using different weight percentages (0.025%, 0.05% and 0.1%) of a non-toxic bismuth catalyst. The bismuth-catalyzed foams presented a well evolved cellular structure with an open cell morphology. The properties of the bismuth-catalyzed flexible PUF, such as the mechanical, morphological, kinetic and thermal behaviors, were optimized and compared with a conventional tin-catalyzed PUF. The bismuth-catalyst revealed a higher isocyanate conversion efficiency than the stannous octoate catalyst. When comparing samples with similar densities, the bismuth-catalyzed foams present better mechanical behavior than the tin-catalyzed sample with similar thermal stability. The high solubility of bismuth triflate in water, together with its high Lewis acidity, have been shown to benefit the production of PU foams., This research was funded by the State Research Agency of Spain (AEI) through grant PID2019-107501RB-I00

Polyurethane foams (PUFs) are a significant group of polymeric foam materials. Thanks to their outstanding mechanical, chemical, and physical properties, they are implemented successfully in a wide range of applications. Conventionally, PUFs are obtained in polyaddition reactions between polyols, diisoycyanate, and water to get a CO foaming agent. The toxicity of isocyanate has attracted considerable attention from both scientists and industry professionals to explore cleaner synthesis routes for polyurethanes excluding the use of isocyanate. The polyaddition of cyclic carbonates (CCs) and polyfunctional amines in the presence of an external blowing agent or by self-blowing appears to be the most promising route to substitute the conventional PUFs process and to produce isocyanate-free polyurethane foams (NIPUFs). Especially for polyhydroxyurethane foams (PHUFs), the use of a blowing agent is essential to regenerate the gas responsible for the creation of the cells that are the basis of the foam. In this review, we report on the use of different blowing agents, such as Poly(methylhydrogensiloxane) (PHMS) and liquid fluorohydrocarbons for the preparation of NIPUFs. Furthermore, the preparation of NIPUFs using the self-blowing technique to produce gas without external blowing agents is assessed. Finally, various biologically derived NIPUFs are presented, including self-blown NIPUFs and NIPUFs with an external blowing agent., This research is part of grant PID2020-119546RJ-I00 funded by MCIN/AEI/10.13039/501100011033.

In this study, a cellulose nanomaterial (Cellulose nanofiber, CNF) was employed as solid support and stabilizing agent for the highly active cobalt nanoparticles via in situ green and facile synthesis as an environmentally benign supported catalyst. The process of preparation involves the reduction of cobalt precursors on the surface of CNF in ambient conditions with the presence of NaBH4. The structure of the synthesized organic-inorganic hybrid Co/CNF was characterized by field emission scanning electron microscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy. The hybrid aerogel nanocomposite Co/CNF demonstrated excellent catalytic activity for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in water with NaBH4. Even with a very low amount of catalyst and was found to be good enough to achieve 100% reduction of 4-NP with a higher reaction rate (in 8 min). The heterogeneous nanocomposite catalyst was easily isolated from the reaction mixture by simple filtration and reused 5 times without significant loss of its catalytic activity.

International audience; The controlled ring-opening polymerization of ϵ‑caprolactone in bulk catalyzed by ionic liquids, thus, avoiding the use of metal catalyst, solvent and base, is reported. These mild conditions led to living polymerization with good conversions and molecular weight distributions of poly(ϵ‑caprolactone). Finally, an activation mechanism is suggested based on the results of an in-situ FTIR polymerization analysis using various ionic liquid catalysts.

Natural polymers, especially polysaccharides, are explored for application in heterogeneous catalysis as immobilization support for metallic or organometallic catalysts. In this work, we designed a green Pd(0) based supported catalyst for Heck C-C coupling reactions. The support was produced from Nanofibrillated Cellulose (NFC) extracted from the rachis of date palm tree. The NFC was prepared by mechanical and chemical pretreatment by mean of TEMPO oxidation of the palm tree cellulose pulp. The Pd(0)-supNFC catalyst was characterized by mean of FTIR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and elementary analysis (EDX), and tested on Heck cross-coupling reaction in comparison with Pd(OAc)2 with the same reaction under homogeneous conditions. Notable properties were found: eco-friendly processing, good reaction yields, very short reaction times, easy separation and reusability with insignificant loss of catalytic activity. More precisely the catalytic tests showed that the Pd(0)-supNFC catalyst has an excellent reactivity with a high reaction yield (90%) with low catalyst loading and short time reaction. In addition, the catalyst retained its activity even after three cycles.

A three-component, one-pot, stepwise Sonogashira–­heterocyclization–Heck-coupling process was developed starting from either haloarenecarboxamides, halophenols or haloanilines, terminal alkynes and electron-deficient alkenes. Cyclic imidate-, benzofuran-, or indole-type products are obtained, respectively, in useful yields, being typically better than those obtained with isolation of the intermediate Sonogashira adducts. Very high 6-endo selectivity is maintained with imidate-type coupling products despite the presence of copper salts carried over from the Sonogashira coupling.

A stepwise protocol is developed for the three-component process using halobenzamides, alkynes, and ethyl acrylate.

International audience; Simple unsaturated and cyclopropylic isocyanides are synthesized by an efficient and simple approach. These compounds with gradually increasing distance between the unsaturated moiety and the isonitrile group are studied by UV photoelectron spectroscopy and quantum chemical calculations, and also compared to the corresponding nitriles. The first photoelectron band of the unsaturated compounds is linked to removal of an electron from the HOMO, which corresponds to CC multiple-bond ionization in antibonding interaction with the π-isocyanide bond (in the same plane) for conjugated systems, or in antibonding interaction with the pseudo-π-CH 2 group for isolated systems. For the 1-ethenyl derivatives, both cyano and isocyano groups act as a π-electron acceptor from the vinyl group, but the isocyano π system is much more strongly destabilized (ionization energies (IEs) shift to smaller values) by vinyl (3.12 eV) than the cyano π system is (2.70 eV). In comparison with the 1-ethynyl derivatives, a less pronounced destabilization (2.69 eV) of π NC by the ethynyl system (1.86 eV for π CN), and nearly the same order of magnitude of the energetic gap between the total antibonding (π CC-π NC) and the total bonding (π CC+π NC) IEs for ethenyl and ethynyl compounds are noted. The huge values of these last-named data for H 2C=CH-NC (3.85 eV) and for HC≡C-NC (4.04 eV) reflect the strong interaction between the unsaturated carbon-carbon moiety and the isocyanide group, and thus more efficient conjugation than for the corresponding nitriles.