A novel catalyst Pd@ompg-C3N4 for highly chemoselective hydrogenation of quinoline under mild conditions

► Selective hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline was realized under mild conditions. ► We developed the novel, active Pd@mpg-C3N4 and Pd@ompg-C3N4 for this process. ► A number of substituted quinolines can be selectively hydrogenated by this system successfully. ► Possible mechanisms of hydrogenation of quinoline on Pd@C3N4 were proposed. ► These catalysts possess good reusability.