p-Hydroxybenzene diazonium salt was utilized to selectively functionalize metallic single-walled carbon nanotubes (SWNT) at 45°C with high selectivity. Deprotonation in alkaline solution induces a negative charge on the functionalized SWNT for electrophoretic separation. We applied this concept to enrich metallic and semiconducting fractions separately using the induced differences in electrophoretic mobilities. Free solution electrophoresis was utilized to separate selectively reacted samples into nonmobile and negative electrophoretic mobility fractions. Raman spectroscopy and UV-vis-nIR absorption spectroscopy confirm both the separation of reacted and unreacted SWNT, and after annealing, the enrichment of metallic and semiconducting SWNT respectively in two distinct fractions.