The photosensitive unit and conjugation play a significant role in photocatalytic performance of covalent organic frameworks (COFs). In this work, a series of COFs that introduced the phenyl phenanthridine as photosensitive unit with different planarity of linkages were synthesized and the common regulation between them for photocatalysis hydrogen evolution reaction (HER) was also studied. The results indicate that DHTB-PPD, with 2/3 planarity linkages (β-ketoenamine/imine is 2/3) and the phenyl phenanthridine as building blocks, shows the narrowest bandgap and the strongest charge separation efficiency. Therefore, it shows the highest H2 production rate of 12.13 mmol g-1 h-1. The optimal photocatalytic efficiency of DTHB-PPD can be attributed to the combined effect of the photosensitive unit and the long-range ordering of the COF skeleton. According to The Density Functional Theory (DFT), the O site on β-ketoamine is the most possible H2 generation site, but the photocatalytic efficiency of TP-PPD, with the highest skeletal conjugation and the highest proportion of β-ketoamine is not the most efficient photocatalyst, indicating that the long-range ordering of COFs is important on photocatalytic performance. Thus, these findings provide valuable guidance for the structural design of COFs photocatalysts.

Porous silicon (Si) has a tetrahedral structure similar to that of sp3- hybridized carbon atoms in a typical diamond structure, which affords it unique chemical and physical properties including an adjustable intrinsic bandgap, a high-speed carrier transfer efficiency. It has shown great potential in photocatalysis, rechargeable batteries, solar cells, detectors, and electrocatalysis. This review introduces various porous Si-supported electrocatalysts and analyzes the reasons why porous Si is used as a new carrier/active sites from the perspectives of its molecular structure, electronic properties, synthesis methods, etc. The electrochemical applications of porous Si-based electrocatalysts in energy conversion reactions such as hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, and total water decomposition together with lithium-ion batteries (LIBs) and supercapacitors in energy storage are summarized. The challenges and future research directions for porous Si are also discussed. This review aims to deepen the understanding of porous Si and promote the development and applications of this new type of Si material.

Mo carbide is recognized as one of the most promising catalyst for CO2 utilization via reverse water-gas shift (RWGS). However, it always suffered from low processing capacity, undesired products and deactivation. Herein, an Ir modified MoO3 synthesized by the flame spray pyrolysis (FSP) method exhibits higher reaction rate (63.0 gCO2·gcat-1·h-1) compared to the one made by traditional impregnation method (45.8 gCO2·gcat-1·h-1) over the RWGS reaction at 600°C. The distinguishing feature between the two catalysts lies in the chemical state and space distribution of Ir species. Ir species predominated in the bulk phase of MoO3 during the quenching process of the FSP method and were mainly in the metallic states, which revealed by X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) characterizations. In contrast, the Ir introduced via impregnation method were mainly on the surface of MoO3 and in oxidized state. The regulation of Ir dopant in MoO3 catalyst by different methods determines the carbonization process to Mo carbides, and thus affects the catalytic performance. This work sheds light on the superiority of the FSP method in synthesizing Mo oxides with heteroatoms and further creating an efficient Mo-based catalyst for CO2 conversion.

Effective conversion of methane to a mixture of more valuable hydrocarbons and hydrogen under mild conditions is a great scientific and practical challenge. Here, we synthesized Zn-containing nanosized MFI zeolite for direct oxidation of methane in the presence of H2O and air. The presence of the surface hydroxyl groups on nanosized MFI-type zeolite and their significant reduction in the Zn-containing nanosized MFI zeolite were confirmed with Infrared Fourier Transform (FTIR) spectroscopy. Incorporation of zinc atoms into the framework of nanosized MFI zeolite is revealed by Nuclear Magnetic Resonance, X-ray Diffraction a UV-Vis Spectroscopy. Unexpectedly, pure silica MFI zeolite exhibited the highest photocatalytic performance. Our finds demonstrated that large number of isolated silanol groups and silanol nests increase the formation of •OH, and enhance the productivity of oxygenate compounds and C2H6, while the Zn incorporated into the zeolite framework or attached to the silanol nests of the nanosized zeolites are less efficient. A mechanism of photocatalytic methane oxidation is proposed. These findings provide insights into developing active nanosized zeolite photocatalysts with extended amount of surface hydroxyl groups that can play a key role in photocatalytic methane conversion.

Despite being promoted as a superior Li-ion conductor, lithium lanthanum zirconium oxide (LLZO) still suffers from a number of shortcomings when employed as an active ceramic filler in composite polymer-ceramic solid electrolytes for rechargeable all-solid-state lithium metal batteries. One of the main limitations is the detrimental presence of Li2CO3 on the surface of LLZO particles, restricting Li-ion transport at the polymer-ceramic interfaces. In this work, a facile way to improve this interface is presented, by purposely engineering the LLZO particle surfaces for better compatibility with a PEO:LiTFSI solid polymer electrolyte matrix. It is shown that an surface treatment based on immersing LLZO particles in a boric acid solution can improve the LLZO surface chemistry, resulting in an enhancement in the ionic conductivity and cation transference number of the CPE with 20 wt.% of boron-treated LLZO particles compared to the analogous CPE with non-treated LLZO. Ultimately, an improved cycling performance and stability in Li // LiFePO4 cells was also demonstrated for the modified material.

Lactones has gained increasing attention in recent years due to wide application in polymer and pharmaceutical industries. Traditional synthetic methods of lactones often involve harsh operating temperature, use of strong alkalis and toxic oxidants. Therefore, lactonization of diols under milder conditions have been viewed as the most promising route for future commercialization. A variety of metal catalysts (Ru, Pt, Ir, Au, Fe, Cu, Co, and Zn) have been developed for highly efficient oxidant-, acceptor-, base- and additive-free lactonization processes. However, only a few initial attempts have been reported with no further details on catalytic mechanism being disclosed in literature. There demands a systematic study of the mechanistic details and the structure-function relationship to guide the catalyst design. In this work, we critically reviewed and discussed the structure-function relationship, the catalytic reaction mechanism, the catalyst stability, as well as the effect of oxidant and solvent for lactonization of diols. This work may provide additional insights for the development of other oxygen-containing functional molecules for material science and technologies.

Ultra-lightweight materials often face the formidable challenge of balancing their low density, high porosity, high mechanical stiffness, high thermal and environmental stability, and low thermal conductivity. This study introduces an innovative method for synthesizing high-performance polymer aerogels to address the challenge. Specifically, we detail the production of poly (2,5-dihydroxy-1,4-phenylene pyridine diimidazole) (PIPD or M5) aerogels. This process involves chemically stripping M5 "super" fibers into nanofibers, undergoing a Sol-Gel transition, followed by freeze-drying and subsequent thermal annealing. The M5 aerogels excel beyond existing polymer aerogels, boasting an ultralight density of 6.03 mg cm-3, superior thermal insulation with thermal conductivity at 32 mW m-1 K-1, inherent flame retardancy (LOI = 50.3%), 80% compression resilience, a high specific surface area of 462.1 m2 g-1, and outstanding thermal stability up to 463 °C. These multi-faceted properties position the M5 aerogel as a front-runner in lightweight insulation materials, demonstrating the strategic use of high-performance polymer assembly units in aerogel design.

Laccases are biocatalysts with immense potential in lignocellulose biorefineries to valorize emerging lignin monomers for sustainable chemicals. Despite reduced costs over the past two decades, enzymes remain a major expense in biorefining. Protein engineering can enhance enzyme properties and lower costs further. In this study, we used enzyme engineering tools to improve > 400-fold the catalytic efficiency (kcat/Km) of a hyperthermostable bacterial laccase for 2,6-dimethoxyphenol, a lignin-related phenolic compound. Furthermore, this evolved variant showed improved activity at neutral to alkaline pH for hydroxycinnamyl alcohols, hydrocinnamic acids, phenylpropanoid and vanillyl derivatives. We optimized conditions for the synthesis of syringaresinol, dehydrodiconiferyl alcohol, thomasidioic acid, biseugenol, dehydrodiisoeugenol, and diapocynin, detailing the pH, catalyst concentration, reaction time, temperature, and oxygenation of the reaction mixtures. Our biocatalytic system offers several advantages, including being free of organic solvents, achieving faster reaction times, using lower amounts of enzymes and delivering excellent yields (up to 100%) than reported methods. Additionally, we provide insights that advance the state-of-the-art in lignin combinatory chemistry. This progress marks a significant step forward in valorizing the lignin chemicals platform, enabling high yields of dimeric compounds with structural scaffolds that can be exploited in various biotechnological areas, such as medicinal chemistry and polymer synthesis.

irect Air Capture (DAC) is an emerging form of atmospheric carbon dioxide removal. Conventional DAC sorbents utilize swings in temperature and/or pressure, which are energy intensive and hinders large-scale deployment. In this work, we demonstrate a green, aqueous electrochemical DAC system that employs Alizarin Red S (ARS) as an electroactive capturing agent. The system has an estimated minimum theoretical energy requirement of 24.6 kJe/mole of CO2, demonstrated reversible electrochemical behavior over 100 cycles and 205 hours, and maintained an average coulombic efficiency of 100% with an average capacity retention of 99.8%. With a techno-economic analysis, we highlight the impact of current density and electrode surface area on levelized costs, and we describe a path to lower the cost of DAC below US$500 per tonne of CO2.

Lignin is an abundant biobased feedstock, representing the first source of renewable aromatic structures. Thanks to its high functionality in aliphatic hydroxyls (Al-OH), phenolic hydroxyls (Ph-OH) and carboxylic acids (COOH), lignin is an attractive precursor to crosslinked polymer materials. Different biobased macromolecular architectures can be designed from lignins, whose end-of-life should also be considered in the context of a circular bioeconomy. To enhance recyclability of crosslinked polymer networks, the introduction of dynamic linkages to design vitrimers is a promising strategy. In this study, Kraft lignin was chemically modified with succinic anhydride, to prepare a series of modified lignins with a controlled COOH/Ph-OH ratio, exploiting the difference in reactivity between Al-OH and Ph-OH groups. Upon crosslinking with a diepoxy, mixed vitrimer networks with variable ratios between dynamic ester bonds and non-dynamic ether bonds were synthesized. The analysis of their properties evidenced the impact of the non-dynamic linkages on the materials behaviors, including their dynamicity and reprocessing ability. Although the activation energy for bond exchange is increased, non-dynamic linkages do not hinder the reprocessability of these adaptable materials, and provide them high creep resistance. The controlled introduction of non-dynamic linkages appears as a promising strategy to enhance the properties of lignin-based vitrimers.