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HYDRA-CHEM Report Summary

Project ID: 227639
Funded under: FP7-IDEAS-ERC
Country: Germany

Final Report Summary - HYDRA-CHEM (Hydrothermal and Ionothermal Chemistry For Sustainable Materials (HYDRA-CHEM))

This project aimed to develop a novel type of chemistry by using hydrothermal or ionothermal reaction conditions to generate novel materials and polymers in a more sustainable fashion. The big vision is to help and guide chemistry through the raw material change. The abbreviation HYDRA-Chem stands for “Hydrated Ion Chemistry at elevated temperatures”. We also included reaction in concentrated salt solutions and finally organic-salt melt mixtures, while the standard ionic liquids were excluded for the sake of differentiation. The increasing interest in hydrothermal synthesis derives from its advantages in terms of high reactivity of reactants, easy control of solution or interface reactions, formation of metastable and unique condensed phases, less air pollution, and low energy consumption It was the task of the project to show that this also allows to generate novel materials and polymers in a more sustainable fashion The project in itself was split into different sub-targets to enable key intermediary goals with sufficient value and visibility. The progress in the subprojects is listed in the following:

Hybrid Structures from biomass and petrochemicals:
We converted biomass into carbons using hydrothermal carbonization, playing with ionothermal conditions and added functional comonomers both from biological and petrochemical origin. We explored systematically the ability to build in nitrogen, sulfur, and nitrogen/sulfur moieties into the final carbon materials and found out that the materials are superior to other carbons concerning oxidation stability, conductivity, and electrochemical activity in a variety of reactions. This has opened up a field of many secondary papers by other authors. The porous supports were partly so stable that we could use the carbons in cooperation with a catalysis group to run the monooxidation of methanol (a Periana reaction) with very good TONs and under full preservation of the catalyst.
Concerning the influence of salts after systematic studies we found out that borates but also hypersaline conditions have a unusually positive influence on hydrothermal carbonization. Not only that the reaction is significantly accelerated, the resulting structures also show much higher specific surface areas. The resulting carbons are monolithic, highly porous, with high surface area, and stable against water drying. The presumably biggest success up to now by the project was the synthesis of graphene sheets, heteroatom-doped grapheme sheets and holey graphene sheets from ordinary glucose as a starting product by reaction in salt melts (ionothermal conditions). Obviously, glucose as well as its elimination products dissolve in those salt melts and strictly condense towards two-dimensional products.

Polymerization towards novel polymer scaffolds via combinatoric reversible chemistry :
Starting with aramides and imides, we continued to expand the set of polymer reactions to rigid, bio-based molecules and polybenzothiazole polymer frameworks These systems are not only rigid frameworks, but show superior singlet oxygen productivity which makes them valuable photocatalysts. As these structures turned out to be chemically very stable, water reactions can be envisaged, and current work is focussed on using the hydrothermally stable PD-catalyst (ref.14) also for this C-C coupling in aqueous media. In another set of experiments, we analysed the polymerization of formaldehyde under hydrothermal conditions, the so-called “formose-reaction” (ref 16). Rather effectively and with higher yields than under ordinary conditions, we could describe the formation of a broad range of sugars from formaldehyde only, however with a strong maximum at C4 and C5 sugars and only little C6- and higher sugars. This was somewhat exciting, as the focus on ribose and desoxyribose nicely fits to early evolution, peribiotic synthesis schemes, while C6 sugars can obviously only be effectively be obtained in an enzymatic C3 + C3 reaction, i.e. they are late species.
We also continued to work on amino acids and protein fragments, where meanwhile polymerization reactions can be excluded. The rather unexpected reaction cascades which are nevertheless well defined were resolved by using metabolomics techniques, in cooperation with our neighboring sister institute, the MPI for Plant Physiology. Excitingly, the (in this case) hydrothermal reforming created 3 new amino acids and two heterocycles which are structural isomers of nucleobases.

Fragmentation and conversion from otherwise stable organic products:
In this smallest of the three subprojects, we continued to analyze the convertibility of fragments from the biomass cycle which are known to be notoriously resistant against up- or down-conversions. Working on glycerol turned out to be less effective, but our highly efficient route towards “bio-ILs” (ionic liquids from purely sustainable starting products) in water. Recent work provided the development of new catalytic systems which were able to break up lignin into valuable fragments under hydrothermal flow conditions.
It is potentially the most exciting finding of this subgroup of projects that the consecutive ionothermal condensation of ILs in eutectic salt melts brought up a completely new subclass of porous carbons with high electronic conductivities and record values of pore volume and specific surface area. The use of those carbons in electrochemistry and as catalyst is on new record levels and will be continued to be analyzed in the research group.

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