Broader contextCarbon dioxide (56%) and methane (18%) are the two main greenhouse gases emitted today.These gases are produced in many current industrial processes as well as those in prospective areas such as the purification of hydrogen produced from biomass. This is why there is an urgent demand to develop efficient strategies for the separation/storage of CO 2 and CH 4 via processes with minimal environmental impact and affordable costs material. Carbonaceous solid sorbents exhibiting enhanced sorbent capability and recyclability may offer an interesting alternative in economical terms. Thus, it is the core competence of material chemists to develop sustainable synthetic strategies capable to produce carbons with enhanced performance. Within this context, the use of ionic liquids and deep eutectic solvents is gaining increased interest because of the particular features demonstrated by these solvents in number of synthetic processes that allow to minimize the number of reagents used in a particular synthesis while provide an excellent control of both the compositional and structural properties of the resulting materials. Herein, the use of a DES-assisted synthesis provided carbons with an extraordinary capability for low-pressure CO 2 separation from both N 2 and CH 4 based on the molecular sieve effect played by their narrow microporosity.
AbstractIonic liquids and deep eutectic solvents (a new class of ionic liquids obtained by complexion of quaternary ammonium salts with hydrogen bond donors such as acids, amines, and alcohols among others) have been recently used as solvents and even as precursors in the synthesis of carbonaceous materials. Particularly interesting has been the use of long-alkyl-chain derivatives of ionic liquids that, playing the role of structure directing agents, were capable to design the mesopore structure of the resulting carbons. Meanwhile, deep eutectic solvents proved efficacy tailoring the structure comprised between large mesopores and small macropores but the control over the smaller ones (e.g. small mesopores and micropores) is yet a challenge as compared to ILs. Herein, we have used deep eutectic solvents composed of resorcinol, 4-hexylresorcinol and tetraethylammonium bromide for the synthesis of carbon monoliths with a tailor-made narrow microporosity. Behaving as molecular sieves, these carbons exhibited not only good capacities for CO 2 adsorption (up to 3 mmol/g) but also an outstanding -especially at low pressures -CO 2 /CH 4 selectivity.
Phosphorus-doped carbon–carbon nanotube hierarchical monoliths exhibiting energy densities of around 22.6 W h kg−1 at power densities of up to 10 kW kg−1 were capable of functioning as true three-dimensional electrodes in supercapacitor cells.
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