The Renewable and Sustainable Conversion of Chitin into a Chiral Nitrogen‐Doped Carbon‐Sheath Nanofiber for Enantioselective Adsorption

Well‐known hard‐template methods for nitrogen (N)‐doped chiral carbon nanomaterials require complicated construction and removal of the template, high‐temperature pyrolysis, harsh chemical treatments, and additional N‐doping processes. If naturally occurring chiral nematic chitin nanostructures [(C8H13NO5)n] in exoskeletons were wholly transformed into an N‐doped carbon, this would be an efficient and sustainable method to obtain a useful chiral nanomaterial. Here, a simple, sacrificial‐template‐free, and environmentally mild method was developed to produce an N‐doped chiral nematic carbon‐sheath nanofibril hydrogel with a surface area >300 m2 g−1 and enantioselective properties from renewable chitin biomass. Calcium‐saturated methanol physically exfoliated bulk chitin and produced a chiral nematic nanofibril hydrogel. Hydrothermal treatment of the chiral chitin hydrogel at 190 °C produced an N‐doped chiral carbon‐sheath nanofibril hydrogel without N‐doping. This material preferentially adsorbed d‐lactic acid over l‐lactic acid and produced 16.3 % enantiomeric excess of l‐lactic acid from a racemic mixture. Chiral chitin: An N‐doped chiral nematic carbon‐sheath nanofibril hydrogel is prepared from renewable chitin biomass by exfoliation of chitin with calcium‐saturated methanol. The material is used for the chiral resolution of lactic acid and preferentially adsorbs d‐lactic acid over l‐lactic acid, producing 16.3 % enantiomeric excess of l‐lactic acid from a racemic mixture.