Influence of the organic linker substituent on the catalytic activity of MIL-101(Cr) for the oxidative coupling of benzylamines to imines

MIL-101(Cr) having substituents at the terephthalate linker (X = H, NO2, SO3H, Cl, CH3 and NH2) promotes the aerobic oxidation of benzylamines to the corresponding N-benzylidene benzylamines at different rates. MIL-101(Cr)-NO2 was the most active catalyst, about 6-fold more active than the parent MIL-101(Cr). MIL101(Cr)- NO2 does not deactivate significantly upon five consecutive reuses, does not leach the metal to the solution and maintains its crystallinity. MIL-101(Cr)-NO2 is active for a wide range of benzylamines including para-substituted, heterocyclic benzylamines and di-and tribenzylamines.