Facile Adjusting of a Right-Handed Helical Structure of Cellulose-Based Carbon Material for Chiral Separation

Cellulose-based carbon ribbons with a right-handed helical/torsional morphology were directly obtained by facile carbonization of microcrystalline cellulose. The right-handed helical carbon ribbons are about 50 μm in length and less than 10 μm in diameter. The thermal behavior of cellulose at low-temperature pyrolysis was investigated by thermogravimetry, mass spectrum, Fourier transform infrared, nuclear magnetic resonance, X-ray photon spectroscopy, and electron spin resonance, and the formation mechanism of the right-handed helical morphology was analyzed. It indicated that the inter- and intramolecular hydrogen bond breaking was the initially triggered factor of helical morphology formation of the cellulose-based carbon, enabling torsion freedom of cellulose molecular chains. Subsequent elimination reaction on C-2 and C-3 resulted in regular vacancies in the cellulose molecular chain, accelerating the formation of helical morphology. After carbonization, abundant "S-like space" lattice finger spaces were originated in the right-handed helical cellulose-based carbon matrix. It showed a certain enantioseparation performance for racemic tartaric acid owing to high adsorption capacity for l-tartaric acid. Moreover, the chiral selectivity of resultant cellulose-based carbon was promoted by a fast heating rate during carbonization. This work presented a feasible strategy to design novel enantioselective carbon materials with potential application in chiral separation.