From the grafting of NHC-based Pd(II) complexes onto TiO2 to the in situ generation of Mott-Schottky heterojunctions: The boosting effect in the Suzuki-Miyaura reaction. Do the evolved Pd NPs act as reservoirs?

•Immobilization of chelating-NHC-based Pd complexes on TiO2 NPs.•Larger chelate rings yield to superior catalytic performances.•TiO2 serve both as support and as catalytic boosting tool in the Suzuki-Miyaura reaction.•The evolved Pd NPs act as reservoirs of active Pd species.•The grafted and ungrafted Pd complexes exhibit a dissimilar catalytic mechanism.