Achieving long-term oxidative stability in proton exchange membrane fuel cells (PEMFCs) remains a major challenge. Here, we investigate the morphological mechanisms underlying the oxidative stability of thiourea-functionalized sol-gel (SG)/sulfonated poly(ether ether ketone) (sPEEK) hybrid membranes, previously developed using two organosilane precursors, N,N '-bis[3-(triethoxysilyl)propyl] thiourea (HTU) and N-phenyl,N '-[3-(triethoxysilyl)propyl] thiourea (TTU). These thiourea groups, introduced as sacrificial antioxidants, are used to tune the nanoscale organization of the SG phase within the polymer matrix. Contrast-variation small-angle neutron scattering (CV-SANS) shows that the SG phase is distributed within ionic nanochannels and interbundle regions. Although TEM and AFM indicate homogeneous dispersion at the microscale, sub-resolution fluctuations likely account for the SANS signal. HTU forms well-defined spherical hybrid domains (similar to 5-6 nm), whereas TTU produces larger, less organized structures (similar to 18-22 nm). Under oxidative conditions, pristine sPEEK swells and degrades above 0.1 wt%, whereas hybrid membranes retain structural integrity and conductivity up to 0.3 wt% through a two-stage protection mechanism, consisting of a primary (total) SG-driven protection in ionic domains followed by a secondary protection in interbundle regions upon SG consumption. This sequential mechanism governs membrane integrity and proton transport under oxidative stress.

Upcycling of polyethersulfone (PES), a high-performance polymer based on an aromatic-rich aryl-ether-based backbone, can advantageously yield both starting Bisphenol S (BPS) comonomer and valuable OLED derivatives, providing complete atom valorisation strategy for PES waste. Deprotonated selected amines proved particularly efficient at depolymerizing PES at moderate temperatures (~ 120 °C). The recycled monomer yields validate the back-to-monomer chemical recycling method for industrial compliance. The OLED derivatives afforded by the same simple process can easily be isolated and promote an innovative upcycling strategy using polymer-to-valuable chemicals, a very relevant approach to help tackle the ever-growing plastic waste remediation.

The utilization of carbon dioxide (CO2) to synthesize various chemicals is of great importance. Herein, various azaphosphatranes and silver salts were applied to catalyze the carboxylative cyclization of CO2 and propargylic alcohols to prepare α-methylene cyclic carbonates. The influences of catalyst structures, solvents and reaction parameters on catalytic performance were systematically studied. The combination of tris(4-methoxybenzyl) azaphosphatranes (PMB-AZAP) and Ag2O with molar ratio of 0.5:1 gave α-methylene cyclic carbonate in the yield of >99% at room temperature. Meanwhile, other azaphosphatranes (i-Bu-AZAP, Me-AZAP) gave the product in slightly lower yields. The mechanism exploration revealed that PMB-AZAP and Ag2O formed a silver complex PMB-AZAP-Ag during the reaction, which could synergistically catalyze carboxylative cyclization reaction with PMB-AZAP, resulting in a high product yield. In contrast, AgCl or AgNO3 couldn’t react with PMB-AZAP to form silver complexes, and the corresponding catalytic system had no activity. The difference of the catalytic performance indicated that PMB-AZAP-Ag was a key active species for the carboxylative cyclization reaction. The in situ NMR studies concretely demonstrated that PMB-AZAP could activate propargylic alcohols through hydrogen bonding. Furthermore, the catalytic system had good substrate generality. The PMB-AZAP/Ag2O was also applied for the one-pot reaction of propargylic alcohol, CO2 and CH3OH, affording the β-carbonyl carbonate with yield of 80% at CH3OH/propargylic alcohols ratio of 20:1.

The cost of proton-exchange membrane fuel cells (PEMFCs) comes mainly from platinum nanoparticles, which are used as a catalyst; it represents 40% of the stack price for large-scale production. It is thus crucial to reduce their cost to produce cheaper devices, which could compete with fossil energy on the industrial market. One way to reach this goal would be to recover the Pt catalyst from the membrane electrode assembly (MEA) for further recycling. For now, current end-of-life (EoL) technologies are mainly based on hydrometallurgical and pyro-hydrometallurgical processes for recovering platinum, which are identified to be energy-demanding and generate high amounts of toxic liquids and gaseous effluents. To meet sustainability and circular economy criteria in the recycling of noble metals, our approach was based on the use of ionic liquids (ILs) to both extract and stabilize platinum in the form of metallic nanoparticles (Pt NPs), thus avoiding the use of strong acids and the emissions of hydrofluoric acid (HF), which make the waste management of conventional processes complicated. Thirteen different ILs were selected to investigate how their structural composition as well as their physicochemical properties may affect the extent of Pt extraction, and their ability to stabilize detached nanoparticles. This screening study showed that ionic liquids could interact with all of the elements of the active layer and allowed us to delineate the key parameters that ILs should possess to achieve the best extraction performance: hydrophilicity, hydrogen bonding ability, and the coordinating ability of the anions. The best result was obtained with trihexyltetradecylphosphonium chloride (P66614Cl, commercial Cyphos IL 101; 120 degrees C and 6 h), which not only led to an extraction extent up to >90% of the Pt present initially on the catalytic layer but also allowed in a single step to detach the Pt NPs from the carbon support. The metallic Pt NPs suspended in P66614Cl were found stable with diameters of around 2-3 nm, as evidenced by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) analyses. Compared to conventional processes, this safer and convenient route to recover Pt catalysts from MEAs directly in their metallic form by simple immersion of the electrode in the appropriate IL opens up new perspectives in terms of rare earth metal recycling from material composites.

The carbonatation of semi-crystalline [ethylene–glycidyl methacrylate] copolymers was achieved in batch and solvent-free reactive extrusion processes. Using CO2as reagent and ammonium salts as catalysts, we turn the epoxides into cyclic carbonates.

This work focuses on the impact of sulfonated poly(ether ether ketone) (sPEEK) membrane pretreatments on fuel cell performance, starting from two different batches of Fumapem E730 from Fumatech, acquired in 2019 and in 2020. sPEEK membranes are possible lower cost alternatives to perfluorosulfonic acid (PFSA) membranes for proton exchange membrane fuel cells (PEMFC) applications. Before use, they must be pretreated to ensure a complete protonic substitution and removal of residual reagents/solvent: the simplest protocol consists in soaking the membrane in an acid solution followed by a rinsing step in water. In addition to this acidification step, hydrothermal (HT) treatments in water at high temperature for a few hours to a few days were also considered herein, as well as a hydro-alcoholic (HA) step, because of their expected effects on membrane nanostructure. Overall, four different protocols were used. The membrane water uptake, water self-diffusion, proton conductivity, and fuel cell performance-under H-2/O-2-were measured. It was found that in the best case-membranes from the 2020 batch subjected to HA followed by 72 h HT pretreatments-the fuel cell performances exceeded those obtained with a PFSA membrane (Nafion XL). This is explained by a higher protonic conductivity, probably resulting from a better sPEEK nano-structuration.

We reported a safer and greener process than those usually based on pyro-hydrometallurgical technologies to recover the Pt catalyst from membrane electrode assemblies (MEAs) without the need for the calcination step and dissolution of platinum nanoparticles (Pt NPs). Using a large panel of ionic liquids (ILs) with different physicochemical properties and varied cation/anion compositions, ILs were used as both extractants to recover directly the Pt NPs from the catalyst layer (CL) of MEAs as well as the stabilization agent of the detached Pt NPs. Our optimized process results in the extraction of metallic Pt up to >90% of the Pt initially present on the CL and also allows in a single step to detach the Pt NPs from its carbon support. Moreover, contact angle measurements revealed that ILs could interact with all the components of the active layer. Among the different interactions allowing the best results in terms of extraction, the Nafion-IL interaction seems to be of particular importance. Indeed, the variation of the ionomer content in the CL was directly correlated with the efficiency of extraction. Therefore, the interaction and wettability of ILs with the different components of the CL and particularly with the ionomer (swelling) are of prime importance and necessitate further studies to deepen our understanding of the mechanism of platinum extraction by ILs. This is the aim of the present detailed study, based on small-angle X-ray scattering and wide-angle X-ray scattering techniques, with a particular focus on the best IL candidate P66614Cl with membrane Nafion as a model system and with the ionomer contained in CL.

Haloazaphosphatranes are the halogenated parents of proazaphosphatranes, also known as Verkade's superbase. While the synthesis of iodo-, bromo- and chloroazaphosphatranes was reported more than thirty years ago by J. G. Verkade, the first synthesis of fluoroazaphosphatranes was only described in 2018 by Stephan et al. Currently, no common and versatile procedure exists to access fluoroazaphosphatranes platform with different structural characteristics. In this report, a new and simple synthesis of this class of compounds was developed based on the nucleophilic attack of the fluoride anion on chloroazaphosphatrane derivatives with good to high isolated yields for the corresponding fluoroazaphosphatranes (70-92%). The scope of the reaction was widened to fluoroazaphosphatranes bearing various substituents and X-ray molecular structures of two of them are reported. The stability of fluoroazaphosphatranes toward nucleophilic solvents like water has been investigated. As they revealed much more robust cations than their chloroazaphosphatrane parents, their chloride salts were tested as organocatalysts for the formation of cyclic carbonates from epoxides and CO2. Fluoroazaphosphatranes proved to be both efficient and stable catalytic systems for CO2 conversion with catalytic activities similar to those of azaphosphatranes, and no decomposition of the cation was observed at the end of reaction.

The covalently heterogenisation of a free-base porphyrin on SBA-15 silica yielded TPPH2@SBA-15 (TPPH2 = tetraphenyl porphyrin), which was very efficient to promote the CO2 cycloaddition to three -membered rings. The TPPH2@SBA-15/TBAX-based catalytic procedure was very general, as revealed by excellent activities registered in the reaction of CO2 with epoxides, N-alkyl and N-aryl aziridines, forming cyclic carbonates, N-alkyl and N-aryl oxazolidinones, respectively. It is worth noting that this is the first example of the heterogeneously catalysed synthesis of N-aryl oxazolidinones from corresponding N-aryl aziridines. The scale-up of the methodology highlighted that catalytic performances of all the three investigated reactions were maintained also working at a gram-scale to pave the way for future developments of the procedure. In addition, the recycle of TPPH2@SBA-15 for several consecutive reactions was efficient and observed catalytic activities were very similar to those registered in the presence of a fresh material. All the acquired data indicated an excellent sustainability of the catalytic protocol to envisage upcoming practical applications. (C) 2022 Elsevier Inc. All rights reserved.

Porous ionic liquids combining alkylphosphonium halides with ZIF-8 absorb large amounts of carbon dioxide that can be catalytically coupled with epoxides to form cyclic carbonates. High activity and selectivity under mild reaction conditions points towards a new promising, high-performing, sustainable family of sorbents for simultaneous carbon capture and transformation.

We report on the synthesis of C-3-symmetric enantiopure cage molecules 1, which exhibit remarkable to exclusive enantioselective recognition properties toward chiral ammonium neurotransmitters. Strong changes in the substrate selectivity are also observed when different stereoisomers of 1 are used. Furthermore, protonation/deprotonation induces a reversible modification of the conformation of 1, which switches from an imploded to an inflated form, leading to ejection and reuptake of the guest initially encaged inside the cavity.

Azaphosphatranes were found to act as efficient organocatalysts in the presence of water for the cyanation of differently substituted imines. A relatively safer source of cyanide, trimethylsilyl cyanide (TMSCN), was used, and excellent yields could be obtained with only 0.05 mol % of catalyst. The influence of acidity of azaphosphatranes on catalytic activity as well as the role of azaphosphatranes in the mechanism of the reaction were also investigated.

Volatile organic compounds (VOCs) are mostly toxic and hazardous substances that generally have a strong odor and can cause health and environmental problems. It is thus of upmost importance for the polymer manufacturing industry to eliminate these volatiles from the synthesized polymers. The properties and the application of the polymer, as well as the nature and the concentration of volatiles, govern the choice of the most appropriate elimination technique to avoid any modification or degradation of the polymer. In this review, we take stock of the most suitable purification methods currently used to remove VOCs from polymers in bulk and in emulsion with particular emphasis on the equipment and experimental requirements for each method, as well as the theoretical considerations that motivate the use of the method. In addition to conventional techniques, we are also presenting our efforts to identify potentially promising alternatives for reducing the VOC content from polymers.

The conversion of CO2 into cyclic carbonates in the presence of epoxides is one of the most promising methods to valorize this important C1 building block. Tetrabutylammonium halide salts are known to catalyze this reaction with moderate activity, and often a co-catalyst is added to increase efficiency. Herein, the influence of the addition of ultra-large pore SBA-15 silica on the catalytic activity of tetrabutylammonium halide salts for this reaction has been investigated in detail. Whereas a negative effect of silica was observed for the NBu4Cl catalyst, surface silanols were shown to strongly improve the yield of the reaction when NBu4Br and NBu4I were used as catalysts. The catalytic activity of the NBu4I salt could be increased by a factor of ten when a relevant amount of mesoporous silica was added. This latter catalytic system leads to high yields and selectivity for a wide variety of substrates under mild condition (80°C). Measurement of the activation parameters demonstrated that the rate enhancement is entropically driven: the pre-organization of the reactants and catalyst on the surface leads to a marked decrease of the activation energy of the reaction. A direct comparison between yield improvement induced by the addition of either an amorphous or a mesostructured silica highlights the crucial role played by the shape and concavity of the support.

Verkade's superbases, entrapped in the cavity of enantiopure hemicryptophane cages, have been synthesized with enantiomeric excess (ee) superior to 98%. Their absolute configuration has been determined by using electronic circular dichroism (ECD) spectroscopy. These enantiopure encaged superbases turned out to be efficient chiral derivatizing agents for chiral azides, underlining that the chirality of the cycloveratrylene (CTV) macrocycle induces different magnetic and chemical environments around the phosphazide functions.