ChemSusChem最新文献

Polyurethane (PU), as a thermoset polymer, is extensively utilized in various applications, such as refrigerator foams, sponges, elastomers, shoes, etc. However, the recycling of post-consumed PU poses significant challenges due to its intricate and extensive crosslinking structures. Catalytic hydrogenation is one of the most effective methods for recycling PU waste, nevertheless, there is currently a lack for a hydrogenation catalyst that is both high-performing, recyclable, and cost-effective for breaking down post-consumed PU materials. In this work, model PU and commercial PU were efficiently hydrodegraded into aromatic amines and polyol fractions by using a commercial NiMo/Al₂O₃ catalyst. Notably, the results indicated that PU waste can be efficiently degraded at a pressure of 5 MPa and at a temperature of 185 °C and yielding a significant amount of a valuable chemical monomers. With the assistance of hydrogenation catalyst, the C-N and C-O bonds with low energy barriers inside the polymer are cracked and the polymer hydrogenation process becomes feasible. This study demonstrates the capability of fluidized bed hydrogenation process, employing recyclable heterogeneous catalysts for the recycling of PU waste.

Biotin[6]uril, a chiral, water-soluble and anion binding macrocycle, is formed via dynamic covalent chemistry. In this study, we present a scalable and high-yielding synthesis of biotin[6]uril via a mechanochemical solid-state approach. The optimized protocol involves mechanical grinding of solid d-biotin with paraformaldehyde in the presence of 0.3 equivalents of 48 % aqueous HBr, which functions as a catalyst, template, and liquid grinding additive. This mechanochemical process is carried out in a shaker or planetary mill, followed by aging at an elevated temperature to produce biotin[6]uril with an HPLC yield of up to 96 %. The condensation and macrocyclization reaction was successfully scaled up 82-fold, producing nearly 20 g of biotin[6]uril with a high 92 % isolated yield and 91 % purity. Compared to conventional solution-based method, this mechanochemical approach offers several advantages, including significantly higher yields, shorter reaction times, enhanced scalability, simpler operational requirements, and substantially lower process mass intensity.

The conversion of bio-based molecules into valuable chemicals is essential for advancing sustainable processes and addressing global resource challenges. However, conventional catalytic methods often demand harsh conditions and suffer from low product selectivity. This study introduces a series of bifunctional Pd_xPt_y catalysts supported on TiO₂, designed for achieving selective and mild-temperature catalysis in biomass conversion. Synthesized via a sol immobilization method and characterized by XRF, N₂ physisorption, HRTEM, HAADF-STEM, and XPS, these catalysts demonstrate superior selectivity and activity over monometallic counterparts. In fact, at 20 bar H₂, Pt/TiO₂ show a low selectivity in benzophenone hydrodeoxygenation, favoring the benzhydrol hydrogenation product; similarly, Pd/TiO₂ preferentially form the diphenylmethane hydrodeoxygenation (HDO) product, but with slow conversion rates. The synergistic combination of the two metals in Pd₄Pt₁/TiO₂ drastically improve performance, with 100 % benzophenone conversion and 73 % diphenylmethane selectivity. DFT calculations confirm the synergy between Pd and Pt as the key to drive the activity and selectivity. Additionally, the catalysts also demonstrate high recyclability with minimal performance loss, and have been generalized for the HDO of vanillin and furfural, and in HMF oxidation. Overall, this work highlights the potential of bimetallic catalysts in enabling efficient and selective bio-based molecule conversion under mild conditions.

End-of-life plastics and carbon dioxide (CO₂) are anthropogenic waste carbon resources; it is imperative to develop efficient technologies to convert them to value-added products. Here we report the upcycling of polyethylene terephthalate (PET) plastic and CO₂ toward valuable potassium diformate, terephthalic acid, and H₂ fuel via decoupled electrolysis. This product-oriented process is realized by two electrolyzers: (1) a solid-state-electrolyte based CO₂ electrolyzer and (2) a solid-polymer-electrolyte-based PET electrolyzer. Using a bismuth-based catalyst, the CO₂ electrolyzer showed more than 140 h continuous operation at current of 250 mA, resulting in 850 mL pure HCOOH solution with a concentration of 683 mM. Furthermore, we constructed a solid-polymer-electrolyte electrolyzer with an electrode area of 50 cm² for the electrooxidation of ethylene glycol to formate, achieving 30 A of current at ~1.9 V cell voltage and 80 % formate Faradaic efficiency. With this electrolyzer, we demonstrated the efficient transformation of PET hydrolysate to a mixture of terephthalate and formate. Additionally, combining CO₂ derived HCOOH and PET electrolyte, we obtained recycled terephthalic acid and potassium diformate. This work provides an integrated strategy for the valorization of waste carbon resources with less using external resources.

Catalyst design plays a critical role in ensuring sustainable and effective energy conversion. Electrocatalytic materials need to be able to control active sites and introduce defects in both acidic and alkaline electrolytes. Furthermore, producing efficient catalysts with a distinct surface structure advances our comprehension of the mechanism. Here, a defect-engineered heterointerface of ruthenium doped cobalt metal organic frame (Ru-CoMOF) core confined in MoS₂ is reported. A tailored design approach at room temperature was used to induce defects and form an electron transfer interface that enhanced the electrocatalytic performance. The Ru-CoMOF@MoS₂ heterointerface obtains a geometrical current density of 10 mA^-2 by providing hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at small overpotentials of 240 and 289 mV, respectively. Density functional theory simulation shows that the Co-site maximizes the evolution of hydrogen intermediate energy for adsorption and enhances HER, while the Ru-site, on the other hand, is where OER happens. The heterointerface provides a channel for electron transfer and promotes reactions at the solid-liquid interface. The Ru-CoMOF@MoS₂ model exhibits improved OER and HER efficiency, indicating that it could be a valuable material for the production of water-alkaline and acidic catalysts.

The cleavage and functionalization of carbon-carbon bonds are crucial for the reconstruction and upgrading of organic matrices, particularly in the valorization of biomass, plastics, and fossil resources. However, the inherent kinetic inertness and thermodynamic stability of C-C σ bonds make this process challenging. Herein, we fabricated a glucose-derived defect-rich hierarchical porous carbon as a heterogeneous catalyst for the oxidative cleavage and esterification of C(CO)-C bonds. Systematic investigations revealed that the hierarchical porous structure enhances the adsorption of O₂ and ketones, thereby boosting the catalytic efficiency of defects. This catalyst exhibits performance comparable to that of the reported nitrogen-doped or metal nanoparticle-supported carbon materials, as well as transition metal-based homogeneous catalytic systems. This work deepens our understanding of the reaction process underlying this transformation and provides insights for designing efficient carbon-based materials for oxidative transformations.

To realize the robust anion exchange membrane (AEM)-based water splitting modules and fuel cells, the design and synthesis of tetraarylphosphonium (TAP) cations are described as a new class of cationic building blocks that exhibit remarkable alkaline stability under harsh conditions. TAP cations with highly sterically demanding aromatic substituents were efficiently synthesized from triarylphosphine derivatives and highly reactive arynes, whose alkaline degradation proved to be suppressed dramatically by the sterically demanding substituents. In the case of bis(2,5-dimethylphenyl)bis(2,4,6-trimethylphenyl)phosphonium, for example, approximately 60% of the cation survived for 27 d under the forced conditions (i.e., in 4 M KOH/CD₃OH at 80 °C), while tetraphenylphosphonium degraded completely within 10 min in 1 M KOH/CD₃OH at that temperature. Through the decomposition of the alkaline-stable TAP cations, not only triarylphosphine oxides, which are often reported to form via the nucleophilic attack toward the cationic phosphorus center, but also triarylphosphines were detected, which suggested the presence of other degradation mechanisms due to the sterically demanding aromatic substituents. In kinetic analyses, bis(2,5-dimethylphenyl)bis(2,4,6-trimethylphenyl)phosphonium was found to exhibit 52 times higher stability compared to benzyltrimethylammonium, which is often employed as the cationic building block for AEMs.

We are facing a world-wide shortage of clean drinking water which will only be further exacerbated by climate change. The development of reliable and affordable methods for water remediation is thus of utmost importance. Chlorine (which forms active hypochlorites in solution) is the most commonly used disinfectant due to its reliability and low cost. One drawback is that it reacts with organic pollutants to generate toxic chlorinated byproducts. To mitigate chlorination in water remediation, we have investigated the use of catalytic amounts of charged water-soluble iron porphyrins. These are known to activate hypochlorite to generate high valent oxoiron species. We studied the depletion of the model micropollutant phenol and the accumulation of chlorinated disinfection byproducts under water remediation conditions, using iron porphyrins [(TMPyP)FeCl]Cl₄ and (NH₄)₄[(TPPS)FeCl] as catalysts, by membrane inlet mass spectrometry. Despite bearing opposite charges on the meso-substituent, both iron porphyrins suppress the formation of chlorinated disinfection by-products equally well. To gain further insight, spectroscopic studies were performed. These showed the transient formation of Compound II, followed by either regeneration of the iron(III) porphyrin at low NaOCl concentrations, or total decomposition of the porphyrin complex at high NaOCl concentrations. Potential future directions for modifications of porphyrin-based catalysts are discussed.

Pentose oxidation and reduction, processes yielding value-added sugar-derived acids and alcohols, typically involve separate procedures necessitating distinct reaction conditions. In this study, a novel one-pot reaction for the concurrent production of xylonic acid and xylitol from xylose is proposed. This reaction was executed at ambient temperature in the presence of a base, eliminating the need for external gases, by leveraging Pt-supported catalysts. Initial experiments using commercially available metal-supported carbon catalysts validated the superior activity of Pt. However, a notable decline in recycling performance was observed in Pt/C, which is attributed to the sintering of Pt nanoparticles. In contrast, the synthesized Pt-supported ZrO₂ catalysts exhibited enhanced recycling performance because of the strong metal-support interaction between Pt and the ZrO₂ support. Furthermore, mechanistic insights and density functional theory calculations show that product desorption involves a significantly higher energy barrier compared to substrate adsorption and hydrogenation, highlighting an efficient transfer hydrogenation mechanism leading to equivalent yields of both xylonic acid and xylitol. This study introduces a promising approach for the simultaneous production of sugar-derived acids and alcohols, with implications for sustainable catalysis and process optimization.

Deep eutectic solvents (DESs) are an emerging class of ionic liquids with high tunability and promise for battery applications. In this study, we investigated acetamide-based DESs for Zn batteries, focusing on a synergistic mixture of two known acetamide (Ace)-based DESs: ${\mathrm{Ace}}_4{\mathrm{ZnCl}}_2$ and ${\mathrm{Ace}}_4{\mathrm{ZnTFSI}}_2$ . By combining these two DESs in various ratios, we aimed to enhance ionic conductivity and optimize electrochemical performance while addressing corrosion concerns. The resulting ternary mixtures exhibit superior ionic mobility, with the highest conductivity observed for ${\mathrm{Ace}}_4{(\mathrm{ZnTFSI}}_2{)}_{0.85}{(\mathrm{ZnCl}}_2{)}_{0.15}$ , which balances performance and stability. However, increased ionic mobility introduces crystallization challenges, limiting liquid-phase stability. Despite these challenges, the optimized DES mixture demonstrates excellent cycling performance with reduced overpotentials and acceptable corrosion levels, offering a viable pathway for scalable Zn battery applications.