An efficient and cost-effective procedure for preparation of Fe3O4 nanoparticles and supported Brønsted acidic ionic liquid 1-methyl-3-(3-trimethoxysilylpropyl)imidazolium hydrogen sulfate (Fe3O4-IL-HSO4) as a Brønsted acidic ionic liquid and efficient magnetic catalyst is described, together with its use for one-pot synthesis of polysubstituted quinolines through Friedländer condensation of 2-aminoaryl ketones with 1,3-dicarbonyl compounds under solvent-free conditions. The most noteworthy aspects of this methodology are its environmental friendliness, simplicity of operation, excellent yield within short reaction time, easy product isolation, and excellent reusability potential of the catalyst.