Long-Chain Hydrocarbons from Nonthermal Plasma-Driven Biogas Upcycling.

The burgeoning necessity to discover new methodologies for the synthesis of long-chain hydrocarbons and oxygenates, independent of traditional reliance on high-temperature, high-pressure, and fossil fuel-based carbon, is increasingly urgent. In this context, we introduce a nonthermal plasma-based strategy for the initiation and propagation of long-chain carbon growth from biogas constituents (CO2 and CH4). Utilizing a plasma reactor operating at atmospheric room temperature, our approach facilitates hydrocarbon chain growth up to C40 in the solid state (including oxygenated products), predominantly when CH4 exceeds CO2 in the feedstock. This synthesis is driven by the hydrogenation of CO2 and/or amalgamation of CHx radicals. Global plasma chemistry modeling underscores the pivotal role of electron temperature and CHx radical genesis, contingent upon varying CO2/CH4 ratios in the plasma system. Concomitant with long-chain hydrocarbon production, the system also yields gaseous products, primarily syngas (H2 and CO), as well as liquid-phase alcohols and acids. Our finding demonstrates the feasibility of atmospheric room-temperature synthesis of long-chain hydrocarbons, with the potential for tuning the chain length based on the feed gas composition.

Removal of Pb2+ from Water Using Sustainable Brown Seaweed Phlorotannins.

Bioadsorption is a promising technology to sequester heavy metal ions from water, and brown seaweed has been identified as one of the most appropriate adsorbents as it is abundant, low cost, and efficient at removing various metal ion contaminations. The ability to remove heavy metals from water arises from the high concentration of polysaccharides and phlorotannins in brown seaweed; however, remediation can be hampered by the salinity, location, and coexistence of pollutants in the contaminated water. Maintaining the adsorbent properties of brown seaweed while avoiding the fragility of living organisms could allow for the development of better adsorbents. Herein, we demonstrate that polymerized phlorotannin particles, synthesized from phlorotannins extracted from a species of brown seaweed (Carpophyllum flexuosum), were able to remove 460 mg of Pb2+ from water per gram of adsorbent. Scanning electron microscopy (SEM), attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), and thermogravimetric analysis (TGA) were used to characterize the polymerization process and the polymerized phlorotannin particles. Importantly, there was no direct correlation between the Pb2+ removal capacity and the phlorotannin content of various algal derivatives of three species of brown seaweed, C. flexuosum, Carpophyllum plumosum, and Ecklonia radiata, as all three had similar adsorption capacities despite differences in phlorotannin content. This work shows that naturally abundant, "green" materials can be used to help remediate the environment.

Isopropenyl Esters (iPEs) in Green Organic Synthesis.

The need for greener compounds able to replace conventional ones with similar reactivity is crucial for the development of sustainable chemistry. Isopropenyl esters (iPEs) represent one eco-friendly alternative to acyl halides and anhydrides. This review provides a comprehensive overview of the preparation methodologies and reported synthetic applications of iPEs and, in particular, of isopropenyl acetate (iPAc). Intriguingly, the presence of a C=C double bond adjacent to the ester functionality makes iPEs appealing in different chemoselective organic synthesis transformations. For instance, the acyl moiety is suitable for transesterification reactions in presence of different heteroatom-based nucleophiles (C-, O-, N-, S-, Se-); these reactions are irreversible thanks to the formation of acetone, obtained upon keto-enol tautomerization of the prop-1-en-2-ol (isopropenyl) leaving group. Similarly, the unsaturation contained in the isopropenyl synthon could be selectively exploited in organic synthesis for electrophilic and/or radical additions as well as in metal-catalyzed cross-coupling reactions. To conclude, iPEs recently found major interest in the direct modification of biomass (i.e. lignin or cellulose) and in the implementation of tandem reactions of esterification-acetalization by exploiting the co-formation of acetone during the reaction.

Defect engineering of oxide perovskites for catalysis and energy storage: synthesis of chemistry and materials science.

Oxide perovskites have emerged as an important class of materials with important applications in many technological areas, particularly thermocatalysis, electrocatalysis, photocatalysis, and energy storage. However, their implementation faces numerous challenges that are familiar to the chemist and materials scientist. The present work surveys the state-of-the-art by integrating these two viewpoints, focusing on the critical role that defect engineering plays in the design, fabrication, modification, and application of these materials. An extensive review of experimental and simulation studies of the synthesis and performance of oxide perovskites and devices containing these materials is coupled with exposition of the fundamental and applied aspects of defect equilibria. The aim of this approach is to elucidate how these issues can be integrated in order to shed light on the interpretation of the data and what trajectories are suggested by them. This critical examination has revealed a number of areas in which the review can provide a greater understanding. These include considerations of (1) the nature and formation of solid solutions, (2) site filling and stoichiometry, (3) the rationale for the design of defective oxide perovskites, and (4) the complex mechanisms of charge compensation and charge transfer. The review concludes with some proposed strategies to address the challenges in the future development of oxide perovskites and their applications.

Impact of Surface Defects on LaNiO3 Perovskite Electrocatalysts for the Oxygen Evolution Reaction.

Perovskite oxides are regarded as promising electrocatalysts for water splitting due to their cost-effectiveness, high efficiency and durability in the oxygen evolution reaction (OER). Despite these advantages, a fundamental understanding of how critical structural parameters of perovskite electrocatalysts influence their activity and stability is lacking. Here, we investigate the impact of structural defects on OER performance for representative LaNiO3 perovskite electrocatalysts. Hydrogen reduction of 700 °C calcined LaNiO3 induces a high density of surface oxygen vacancies, and confers significantly enhanced OER activity and stability compared to unreduced LaNiO3 ; the former exhibit a low onset overpotential of 380 mV at 10 mA cm-2 and a small Tafel slope of 70.8 mV dec-1 . Oxygen vacancy formation is accompanied by mixed Ni2+ /Ni3+ valence states, which quantum-chemical DFT calculations reveal modify the perovskite electronic structure. Further, it reveals that the formation of oxygen vacancies is thermodynamically more favourable on the surface than in the bulk; it increases the electronic conductivity of reduced LaNiO3 in accordance with the enhanced OER activity that is observed.

Upgrading of marine (fish and crustaceans) biowaste for high added-value molecules and bio(nano)-materials.

Currently, the Earth is subjected to environmental pressure of unprecedented proportions in the history of mankind. The inexorable growth of the global population and the establishment of large urban areas with increasingly higher expectations regarding the quality of life are issues demanding radically new strategies aimed to change the current model, which is still mostly based on linear economy approaches and fossil resources towards innovative standards, where both energy and daily use products and materials should be of renewable origin and 'made to be made again'. These concepts have inspired the circular economy vision, which redefines growth through the continuous valorisation of waste generated by any production or activity in a virtuous cycle. This not only has a positive impact on the environment, but builds long-term resilience, generating business, new technologies, livelihoods and jobs. In this scenario, among the discards of anthropogenic activities, biodegradable waste represents one of the largest and highly heterogeneous portions, which includes garden and park waste, food processing and kitchen waste from households, restaurants, caterers and retail premises, and food plants, domestic and sewage waste, manure, food waste, and residues from forestry, agriculture and fisheries. Thus, this review specifically aims to survey the processes and technologies for the recovery of fish waste and its sustainable conversion to high added-value molecules and bio(nano)materials.

Interfacial Reactions between Lithium and Grain Boundaries from Anatase TiO2-TUD-1 Electrodes in Lithium-Ion Batteries with Enhanced Capacity Retention.

The synergistic incorporation of anatase TiO2 domains into siliceous TUD-1 was optimized in this work and the resulting sample was implemented as the electrode in lithium-ion batteries. Triethanolamine was used as both the templating and complexing agent, the Si/Ti ratio was controlled, and the formation of Ti-O-Si bridges was optimized, as revealed through Fourier transform infrared spectroscopy, with the porous character of the materials being confirmed with N2 adsorption-desorption isotherms. The controlled formation of Ti-O-Si bridges resulted in attractive specific charge capacities, high rate capability, and a good retention of capacity. The electrochemical performance of the composite material clearly demonstrates a synergistic effect between pure TiO2 in its anatase form and the otherwise inactive siliceous TUD-1 matrix. Specific capacities of 300 mA h g-1 with a retention of 94% were obtained at a current density of 0.1 A g-1 over 100 cycles. This work showcases the use of bifunctional templating agents in the improvement of the performance and the long-term cyclability of composite electrodes, which can be potentially applied in future synthesis of energy materials.

Exploring Opportunities for Platinum Nanoparticles Encapsulated in Porous Liquids as Hydrogenation Catalysts.

The unusual combination of characteristics observed for porous liquids, which are typically associated with either porous solids or liquids, has led to considerable interest in this new class of materials. However, these porous liquids have so far only been investigated for their ability to separate and store gases. Herein, the catalytic capability of Pt nanoparticles encapsulated within a Type I porous liquid (Pt@HS-SiO2 PL) is explored for the hydrogenation of several alkenes and nitroarenes under mild conditions (T=40 °C, PH2 =1 atm). The different intermediates in the porous liquid synthesis (i.e., the initial Pt@HS-SiO2 , the organosilane-functionalized intermediate, and the final porous liquid) are employed as catalysts in order to understand the effect of each component of the porous liquid on the catalysis. For the hydrogenation of 1-decene, the Pt@HS-SiO2 PL catalyst in ethanol has the fastest reaction rate if normalized with respect to the concentration of Pt. The reaction rate slows if the reaction is completed in a "neat" porous liquid system, probably because of the high viscosity of the system. These systems may find application in cascade reactions, in particular, for those with mutually incompatible catalysts.

Hydrothermal Liquefaction of α-O-4 Aryl Ether Linkages in Lignin.

By using lignin model compounds with relevant key characteristic structural features, the reaction pathways of α-O-4 aryl ether linkages under hydrothermal conditions are elucidated. Experimental results and computational modeling suggest that the α-O-4 linkages in lignin undergo catalyzed hydrolysis and elimination to give phenolic and alkenylbenzene derivatives as major products in subcritical water. The decreased relative permittivity of water at these high temperatures and pressures facilitates the elimination reactions. The alkyl group on the α-carbon and the methoxy groups on the phenyl rings both have positive effects on the rate of conversion of α-O-4 linkages in native lignin.

Single-Step Methylation of Chitosan Using Dimethyl Carbonate as a Green Methylating Agent.

N,N,N-Trimethyl chitosan (TMC) is one chitosan derivative that, because of its improved solubility, has been studied for industrial and pharmaceutic applications. Conventional methods for the synthesis of TMC involve the use of highly toxic and harmful reagents, such as methyl iodide and dimethyl sulfate (DMS). Although the methylation of dimethylated chitosan to TMC by dimethyl carbonate (DMC, a green and benign methylating agent) was reported recently, it involved a formaldehyde-based procedure. In this paper we report the single-step synthesis of TMC from chitosan using DMC in an ionic liquid. The TMC synthesised was characterised by 1H NMR spectroscopy and a functionally meaningful degree of quaternisation of 9% was demonstrated after a 12-h reaction time.

The encapsulation of metal nanoparticles within porous liquids.

Herein, we report the first successful encapsulation of metal nanoparticles within a Type I porous liquid. We found that the presence of thiol groups was critical to both the encapsulation and the stabilisation of the metal nanoparticles.

Dynamic Nuclear Polarization NMR Spectroscopy of Polymeric Carbon Nitride Photocatalysts: Insights into Structural Defects and Reactivity.

Metal-free polymeric carbon nitrides (PCNs) are promising photocatalysts for solar hydrogen production, but their structure-photoactivity relationship remains elusive. Two PCNs were characterized by dynamic-nuclear-polarization-enhanced solid-state NMR spectroscopy, which circumvented the need for specific labeling with either 13 C- or 15 N-enriched precursors. Rapid 1D and 2D data acquisition was possible, providing insights into the structural contrasts between the PCNs. Compared to PCN_B with lower performance, PCN_P is a more porous and more active photocatalyst that is richer in terminal N-H bonds not associated with interpolymer chains. It is proposed that terminal N-H groups act as efficient carrier traps and reaction sites.

A New Approach to Understand the Adsorption of Thiophene on Different Surfaces: An Atom Probe Investigation of Self-Assembled Monolayers.

Atom probe tomography was used to analyze self-assembled monolayers of thiophene on different surfaces, including tungsten, platinum, and aluminum, where the tungsten was examined in both pristine and oxidized forms. A glovebag with controlled atmospheres was used to alter the level of oxidation for tungsten. It was shown that different substrates lead to substantial changes in the way thiophene adsorbs on the surface. Furthermore, the oxidation of the surface strongly influenced the adsorption behavior of the thiophene molecules, leading to clear differences in the amounts and compositions of field evaporated ions and molecular ions.

Polymeric carbon nitride for solar hydrogen production.

If solar hydrogen production from water is to be a realistic candidate for industrial hydrogen production, the development of photocatalysts, which avoid the use of expensive and/or toxic elements is highly desirable from a scalability, cost and environmental perspective. Metal-free polymeric carbon nitride is an attractive material that can absorb visible light and produce hydrogen from water. This article reviews recent developments in polymeric carbon nitride as used in photocatalysis and then develops the discussion focusing on the three primary processes of a photocatalytic reaction: light-harvesting, carrier generation/separation/transportation and surface reactions.

Unravelling Some of the Key Transformations in the Hydrothermal Liquefaction of Lignin.

Using both experimental and computational methods, focusing on intermediates and model compounds, some of the main features of the reaction mechanisms that operate during the hydrothermal processing of lignin were elucidated. Key reaction pathways and their connection to different structural features of lignin were proposed. Under neutral conditions, subcritical water was demonstrated to act as a bifunctional acid/base catalyst for the dissection of lignin structures. In a complex web of mutually dependent interactions, guaiacyl units within lignin were shown to significantly affect overall lignin reactivity.

Continuous-Flow O-Alkylation of Biobased Derivatives with Dialkyl Carbonates in the Presence of Magnesium-Aluminium Hydrotalcites as Catalyst Precursors.

The base-catalysed reactions of OH-bearing biobased derivatives (BBDs) including glycerol formal, solketal, glycerol carbonate, furfuryl alcohol and tetrahydrofurfuryl alcohol with non-toxic dialkyl carbonates (dimethyl and diethyl carbonate) were explored under continuous-flow (CF) conditions in the presence of three Na-exchanged Y- and X-faujasites (FAUs) and four Mg-Al hydrotalcites (HTs). Compared to previous etherification protocols mediated by dialkyl carbonates, the reported procedure offers substantial improvements not only in terms of (chemo)selectivity but also for the recyclability of the catalysts, workup, ease of product purification and, importantly, process intensification. Characterisation studies proved that both HT30 and KW2000 hydrotalcites acted as catalyst precursors: during the thermal activation pre-treatments, the typical lamellar structure of the hydrotalcite was broken down gradually into a MgO-like phase (periclase) or rather a magnesia-alumina solid solution, which was the genuine catalytic phase.

Multiphase hydrodechlorination of polychlorinated aromatics - Towards scale-up.

We describe a chemical technology for the reductive catalytic multiphase hydrodechlorination (HDC) of chlorinated aromatics to greatly reduce their toxicity and aid the disposal of such species. The system requires no solvent and the catalyst displays a high recycling efficiency. In the present case, 1,3-dichlorobenzene (1,3-DCB) was used as a model compound, and was quantitatively hydrodechlorinated to benzene with hydrogen, in a tri-phasic liquid system consisting of the chlorinated aromatic itself as the top organic phase, an aqueous sodium hydroxide bottom phase (that neutralises acids formed), and an Aliquat®336 (A336) intermediate phase containing a Pd/C catalyst. Once the reaction was complete the top phase (now just benzene) and the bottom phase (now principally aqueous NaCl) were removed and the remaining catalytic A336/(Pd/C) phase recycled. This model study was conducted on a multi-gram scale with a view of demonstrating its applicability to the detoxification of PCBs. Comparison of the Mass Intensity (MI) and turnover frequency (TOF) of our model reaction with three examples of published procedures for the HDC of DCB, indicated that the MI for our system (MI = 6.33) was lower by an order of magnitude or more than that of the others (MI = 27.9, 64.6, 96016), and that TOFs were comparable. A preliminary cost analysis indicates approximately 2000 €/tonne to treat tonne-scale amounts of chlorinated aromatics, making the system in principle useful for industrial implementation.

Electrochemical investigation of [Co4(µ3-O)4(µ-OAc)4(py)4] and peroxides by cyclic voltammetry.

Two oxidative redox processes of the neutral cobalt(iii) cubane, [Co4(µ3-O)4(µ-OAc)4(py)4], were investigated by cyclic voltammetry at a glassy carbon electrode in acetonitrile. In addition to the first quasi-reversible one-electron oxidation at E1/2 = 0.283 V vs. Fc0/+, a second quasi-reversible one-electron oxidation was observed at E1/2 = 1.44 V vs. Fc0/+. Oxidation at this potential does not facilitate water oxidation. In the presence of tert-butylhydroperoxide the peak current of this second oxidation increases, suggesting oxidation of the peroxide by the doubly oxidised cubane.

Masked N-Heterocyclic Carbene-Catalyzed Alkylation of Phenols with Organic Carbonates.

An easily prepared masked N-heterocyclic carbene, 1,3-dimethylimidazolium-2-carboxylate (DMI-CO2 ), was investigated as a "green" and inexpensive organocatalyst for the alkylation of phenols. The process made use of various low-toxicity and renewable alkylating agents, such as dimethyl- and diethyl carbonate, in a focused microwave reactor. DMI-CO2 was found to be a very active catalyst and excellent yields of a range of aryl alkyl ethers were obtained under relatively benign conditions. The observed difference in the conversion behavior of phenol methylation, in the presence of either the carbene or 1,8-diazabicycloundec-7-ene (DBU) catalyst, was rationalized on the basis of mechanistic investigations. The primary mode of action for the N-heterocyclic carbene is nucleophilic catalysis. Activation of the dialkyl carbonate electrophile results in concomitant evolution of an organo-soluble alkoxide, which deprotonates the phenolic starting material. In contrast, DBU is initially protonated by the phenol and thus consumed. Subsequent regeneration and participation in nucleophilic catalysis only becomes significant after some phenolate alkylation occurs.

A New Methodology for Assessing Macromolecular Click Reactions and Its Application to Amine--Tertiary Isocyanate Coupling for Polymer Ligation.

Click reactions have provided access to an array of remarkably complex polymer architectures. However, the term "click" is often applied inaccurately to polymer ligation reactions that fail to respect the criteria that typify a true "click" reaction. With the purpose of providing a universal way to benchmark polymer-polymer coupling efficiency at equimolarity and thus evaluate the fulfilment of click criteria, we report a simple one-pot methodology involving the homodicoupling of α-end-functionalized polymers using a small-molecule bifunctional linker. A combination of SEC analysis and chromatogram deconvolution enables straightforward quantification of the coupling efficiency. We subsequently employ this methodology to evaluate an overlooked candidate for the click reaction family: the addition of primary amines to α-tertiary isocyanates (α-(t)NCO). Using our bifunctional linker coupling strategy, we show that the amine-(t)NCO reaction fulfills the criteria for a polymer-polymer click reaction, achieving rapid, chemoselective, and quantitative coupling at room temperature without generating any byproducts. We demonstrate that amine-(t)NCO coupling is faster and more efficient than the more common amine-tertiary active ester coupling under equivalent conditions. Additionally, we show that the α-(t)NCO end group is unprecedentedly stable in aqueous media. Thus, we propose that the amine-(t)NCO ligation is a powerful new click reaction for efficient macromolecular coupling.