Synthesis and catalysis of oleic acid-coated Fe3O4 nanocrystals for direct coal liquefaction

► Fifteen nanometer-sized oleic acid-coated Fe3O4 nanocrystals were synthesized. ► The synthesized samples were for the first time applied for direct coal liquefaction. ► Small-sized oleic acid-coated Fe3O4 nanocrystals showed excellent catalytic activity.