Core-shell composites of USY@Mesosilica: Synthesis and application in cracking heavy molecules with high liquid yield

•Synthesis of uniform and thickness-controlled core–shell composites of mesosilica and USY zeolite.•The way ensures Y zeolite has least dealumination and keeps its original acidity after assembled.•The composites exhibit an excellent selectivity of middle distillates in hydrocracking of heavy oil.•Illustrating the self-assembly process of composites and the reason for high catalytic selectivity.•The way can be applied to assemble SBA-15 silica with some materials of nonresistant to acid.