ChemSusChem最新文献

Efficient methods for isolating N-glycans are essential to understanding the functions and characteristics of the entire N-glycome. Enzymatic release using PNGaseF is the most effective approach for releasing mammalian N-glycans for analytical purposes. However, the use of PNGaseF for preparative N-glycan isolation is precluded due to the enzyme's cost and limited stability. In this work, we develop a PNGaseF heterogeneous biocatalyst for the preparative isolation of N-glycans from natural sources. By controlling the immobilization conditions, 100-51 % of offered PNGaseF is immobilized on aldehyde-functionalized agarose porous microbeads through distinct protein orientations, achieving different performances. The enzyme orientation through the N-terminus provides the best activity/operational stability balance, being 20 % more efficient than that randomly oriented. This active and stable heterogeneous biocatalyst eases its application in a packed bed reactor (PBR) for continuous release of free N-glycans from a model glycoprotein. This PBR processes 1 g of ovalbumin from chicken egg white to isolate 95 % of its N-glycans upon operating the PBR for 7 days. Finally, by tuning the flow rate, we can control the profile of N-glycans isolated due to different enzyme kinetics for the deglycosylation reactions. In-line methodologies to isolate N-glycans open new paths for more sustainable protocols to prepare relevant glycans.

This short review explores the enzymatic treatment of lignin in alkaline homogeneous systems, focusing on alkaliphilic laccases. In acidic conditions, native laccases are known to promote lignin polymerization, while the addition of mediators enables depolymerization into valuable small molecules. Alkaliphilic laccases, which remain active in basic pH where the vast majority of industrial lignins are soluble, present an interesting alternative. However, the literature shows varied outcomes - polymerization, depolymerization, or both processes - making it difficult to draw clear trends. This review aims to summarize the current state of the art of the enzymatic treatment of lignin in alkaline conditions.

The Cover Feature shows a floating solar heating system with three key elements: a buoyant carrier with a hierarchical porous structure, a photothermal material that converts solar energy into thermal energy, and a photocatalyst that produces hydrogen. The floating photothermal system uses solar radiation to generate steam, and then with the help of the hierarchical porous structure, the steam quickly diffuses to the active sites to achieve sustainable hydrogen production. More information can be found in the Review by H. Zhao, X. Yu, and co-workers.

Understanding the impact of surface copper valence states on the distribution of electrochemical carbon dioxide products is critical. Herein, CuO@Cu₂O with a Cu²⁺/Cu⁺ interface was fabricated using wet chemical etching approach. The hollow shape offered a large region for gas adsorption, while the interfacial mixed chemical state of Cu²⁺/Cu⁺ with tunable control ratio raised the local density of CHO* and accelerated the carbon-carbon coupling reaction. The H-cell test results demonstrate that, as result of this precise structural design, the Faraday efficiency of ethylene is enhanced from 15.2 % to 43.5 %, and the service life is increased 4 times. In addition, its selectivity is almost 50 % and its partial current density in MEA is 93.2 mA cm^-2. In situ Raman and DFT data demonstrate that the Cu²⁺/Cu⁺ interface effect enhances the concentration of COCHO intermediates and lowers the energy barrier for the conversion of CO* to COCHO* intermediates.

Electrocatalysis in metal-organic frameworks is an interplay between the diffusion of charges, the intrinsic catalytic rate, and the mass-transport of reactants through the pores. Here a systematic study is carried out to investigate the role of the electrolyte nature and concentration on the oxygen reduction reaction (ORR) with the PCN-224(Co) MOF in aqueous electrolyte. It was found that the ORR activity is slightly influenced by the nature of the ions in solution, providing that the ionic strength is high enough to minimize the resistivity during the measurement. The ORR activity was found to be 1.3-1.5 times lower in lithium acetate compared to sodium acetate, while the ORR activity in cesium acetate was 1.3-1.6 times higher compared to the activity in sodium acetate. Moreover, there was no dependency found of the ORR catalysis on the size of the anion, buffer concentration, or oxygen concentration. These findings suggest that ORR catalysis in PCN-224(Co) is limited by the intrinsic ORR rate at the active site rather than charge transport through the porous structure or substrate transport in the pores. Therefore, optimization of ORR catalysis with this MOF might be achieved by the optimization of the electronics at the cobalt active site.

A niobium (Nb) mesh electrode was coated with boron-doped diamond (BDD) using chemical vapor deposition in a custom-built hot-filament reactor. The BDD-functionalized mesh was tested in a zero-gap electrolysis configuration and evaluated for the anodic formation of H₂O₂ by selective oxidation of water, including the analysis of the effects on Faradaic efficiency towards H₂O₂ (FEH2O2) induced by pulsed electrolysis. A low electrolyte flow rate (V⋅_anolyte) was found to result in a relatively high concentration of H₂O₂ in single-pass electrolysis experiments. Regarding pulsed electrolysis, we show an optimal ratio of on-time to off-time to obtain the highest concentration of H₂O₂. Off-times that are "too short" result in decreased FEH2O2, whereas "too long" off-times dilute the product in the electrolyte stream. Using our electrolyzer setup with an anodic pulse of 2 s with 4 s intervals, and a V⋅_anolyte of 0.75 cm³ min^-1, resulted in the best performance. This adjustment increased the FEH2O2 by 70 % compared to constant current electrolysis, at industrially relevant current densities (150 mA cm^-2). Fine tuning of BDD morphology, flow patterns, and anolyte composition might further increase the performance of zero-gap electrolyzers in pulsed operation modes.

The Front Cover shows that potassium carbonate is a highly active solid base catalyst for low-temperature polycarbonate methanolysis in the presence of tetrahydrofuran as solvent. It achieves the lowest activation energy so far for PC methanolysis over a heterogeneous catalyst. More information can be found in the Research Article by K. C.-W. Wu and co-workers.

The Cover Feature presents a three-component strategy to enhance the oxygen reduction reaction (ORR, indicated by the top arrow), delving deep into the profound implications of fine structure by focusing on central atoms (big purple ball), coordinating atoms (gray and orange balls), and environmental atoms (caramel balls). More information can be found in the Review by W. Zhang and co-workers.

The Cover Feature refers to the sustainability of furanic platform chemicals and their derivatives, which are derived from renewable plant materials. It also shows the schematic color profiles of these derivatives′ stability in various solvents. The systematic study of the stability of furanic compounds allows us to assess the feasibility of conducting reactions with these substances under specific reaction conditions. More information can be found in the Research Article by V. P. Ananikov and co-workers (DOI: 10.1002/cssc.202401849). Cover created by Anastasia Golysheva.

At a time when increasing attention is paid to sustainability in chemistry, levulinic acid (LA) is one of the most important platform chemicals for the goal of overcoming our dependence on fossil raw materials. However, a so far limiting obstacle on the way to efficient LA production from biomass is the formation of undesirable humin byproducts. In this work, a new catalytic route for the effective utilization of these humin byproducts, enabling a cyclic synthesis of LA using formic acid (FA) as organocatalyst is proposed. Selective catalytic oxidation (SCO) of humins using the H₅PV₂Mo₁₀O₄₀ (HPA-2) polyoxometalate (POM) catalyst produces FA that can be isolated from the aqueous reaction mixture by using nanofiltration membranes accompanied by a complete catalyst recycling (>99 %). After concentration of FA by distillation, the latter can be used as organocatalyst for LA production from sugars, whereby the formed humins can in turn be separated and used as substrates for further FA production via SCO to close the catalytic cycle. By using FA as a green and sustainable acidic organocatalyst, relatively high yields of LA (up to 42 mol %) could be achieved. In the future this can potentially lead to the creation of a closed cycle for an environmentally friendly and efficient production of green LA without undesired humin formation.