Molybdic acid-functionalized silica-coated nano-Fe₃O₄ particles (Fe₃O₄@SiO₂–MoO₃H) have been prepared as a novel heterogeneous acid catalyst using a facile process. The material was subsequently identified as an efficient catalyst for the synthesis of 1,8-dioxo-decahydroacridine derivatives under solvent free conditions. The catalyst could be readily recovered using a simple external magnet and reused several times without any significant loss in activity. Short reaction time, excellent yields and simple work-up are the advantages of this procedure.