Regina Rothe

Renewable nitrogen-doped hydrothermal carbons derived from microalgae.

Nitrogen-doped carbon materials are synthesized via an effective, sustainable, and green one-step route based on the hydrothermal carbonization of microalgae with high nitrogen content (ca. 11 wt %). The addition of the monosaccharide glucose to the reaction mixture is found to be advantageous, enhancing the fixation of nitrogen in the synthesized carbons, resulting in materials possessing nitrogen content in excess of 7 wt %, and leading to promising reaction yields. Increasing the amount of glucose leads to a higher nitrogen retention in the carbons, which suggests co-condensation of the microalgae and glucose-derived degradation/hydrolysis products via Maillard-type cascade reactions, yielding nitrogen-containing aromatic heterocycles (e.g., pyrroles) as confirmed by several analytical techniques. Increasing the HTC processing temperature leads to a further aromatization of the chemical structure of the HTC carbon and the formation of increasingly more condensed nitrogen-containing functional motifs (i.e., pyridinic and quaternary nitrogen).

Eutectic Syntheses of Graphitic Carbon with High Pyrazinic Nitrogen Content.

Mixtures of phenols/ketones and urea show eutectic behavior upon gentle heating. These mixtures possess liquid-crystalline-like phases that can be processed. The architecture of phenol/ketone acts as structure-donating motif, while urea serves as melting-point reduction agent. Condensation at elevated temperatures results in nitrogen-containing carbons with remarkably high nitrogen content of mainly pyrazinic nature.

Chlorine borrowing: an efficient method for an easier use of alcohols as alkylation agents

Chlorine functionalised tin dioxide nanoparticles proved able to partially convert alcohols into the corresponding chlorides, which act as alkylation agents with an increased electrophilicity, as evidenced on ether formation and Friedel–Crafts reactions.

Modular thiol-ene chemistry approach towards mesoporous silica monoliths with organically modified pore walls.

The surface modification of mesoporous silica monoliths through thiol-ene chemistry is reported. First, mesoporous silica monoliths with vinyl, allyl, and thiol groups were synthesized through a sol-gel hydrolysis-polycondensation reaction from tetramethyl orthosilicate (TMOS) and vinyltriethoxysilane, allyltriethoxysilane, and (3-mercaptopropyl)trimethoxysilane, respectively. By variation of the molar ratio of the comonomers TMOS and functional silane, mesoporous silica objects containing different amounts of vinyl, allyl, and thiol groups were obtained. These intermediates can subsequently be derivatized through radical photoaddition reactions either with a thiol or an olefin, depending on the initial pore wall functionality, to yield silica monoliths with different pore-wall chemistries. Nitrogen sorption, small-angle X-ray scattering, solid-state NMR spectroscopy, elemental analysis, thermogravimetric analysis, and redox titration demonstrate that the synthetic pathway influences the morphology and pore characteristics of the resulting monoliths and also plays a significant role in the efficiency of functionalization. Moreover, the different reactivity of the vinyl and allyl groups on the pore wall affects the addition reaction, and hence, the degree of the pore-wall functionalization. This report demonstrates that thiol-ene photoaddition reactions are a versatile platform for the generation of a large variety of organically modified silica monoliths with different pore surfaces.

The bakery of high-end sorption carbons: sugar–urea doughs as processable precursors for functional carbons

Via utilizing a phenomenon that is usually observed in the food industry, a scalable, safe, and cheap synthesis method for processable and functional porous carbons has been presented. Using simple sugars in combination with urea, low melting liquids can be formed that are also stable at room temperature without recrystallization. Due to low vapor pressure, these melts can be easily stored and handled for further use as carbon precursors. The resulting carbon materials possess high nitrogen content and are obtained in high yield. The liquid precursor state also allows the addition of further substances, and highly porous carbon monoliths can be formed by the introduction of a salt/fiber mixture. Herein, cellulose was found to serve as an efficient additive, which resulted in processable viscoelastic doughs without the alteration of the final carbon properties. This method is of special importance with regard to industrial processes as compared to standard carbonization, and it becomes possible to handle intermediates in a green body fashion. Eventually, compared to pre-baked bread rolls, storable intermediates can be processed which inherently contain already all the final carbon properties. The carbon cookies were stable against oxidation and were shown to be highly suitable as a sorption material, which was demonstrated via dye-removal from an aqueous solution.