Inverse Electron Demand Diels–Alder Reaction on M 3 N@C 80 (M=Lu, Sc): Reactivity and Reversibility Enable Chemical Separation of Metallofullerenes

via retro-cycloaddition upon thermal treatment. With the unusual reactivity and reversibility, the IEDDA reaction enables an effective separation approach for metallofullerenes from their soot extracts, opening path to efficient and economical scale-up synthesis of metallofullerenes in laboratory and industrial settings.