NADES-derived beta cyclodextrin-based polymers as sustainable precursors to produce sub-micrometric cross-linked mats and fibrous carbons

Owing to their tuneable synthesis, good chemical stability, and biocompatibility, beta cyclodextrin (βCD)-based polymers have attracted scientific and industrial attention. Besides, to render their fabrication more sustainable and suitable for large-scale productions, the substitution of toxic compounds and organic solvents with eco-friendly alternatives represents an active field of research. In this context, natural low-cost compounds such as sugars, carboxylic acids, and amino acids, have been extensively reported as suitable precursors to produce the so-called natural deep eutectic solvents (NADES). Furthermore, citric acid/choline chloride NADES systems have been exploited as suitable solvent/reactive media for the synthesis of functional water-soluble βCD-based polymers. In this work, the production of sub-micrometric fibres, from the electrospinning of NADES-derived βCD-based polymer solutions, was investigated, using water as a unique solvent. Also, the possibility to cross-link the obtained fibres via facile thermal treatment, without altering the fibrous morphology was demonstrated. Accordingly, cured, insoluble fibrous mats with mean diameters of 0.61±0.15 µm were obtained. Furthermore, the spun mats were screened as suitable bio-derived precursors to produce porous carbon fibres. Average diameters lower than 500 nm were obtained as a result, while the use of polyethylene oxide as a pore initiation agent, allowed to observe carbon fibres with porosities ranging from 13 to 24 nm. Eventually, the adsorption performances of both the cross-linked mat and the carbon fibres were tested for the treatment of emerging pollutants in contaminated water.