Polycarboxylation of carbon nanofibers under Friedel-Crafts condition: A simple route to direct binding of carboxylic functionalities to graphitic π-system

► CNFs are carboxylated via a combination of Friedel-Crafts reaction with oxalyl chloride and hydrolysis. ► After SOCl2 treatment, OASQ is then covalently attached to the nanofibers through amide linkage. ► OASQ domains are uniformly distributed on the surface, which indicates the distribution pattern of the carboxyl groups.