A simple sol–gel process is followed to construct a thin layer of mesoporous silica shell core–shell structure on micrometer sized and nanometer sized zeolite A (micro-zeolite A@SiO2 and nano-zeolite A@SiO2 respectively). Further thickness of the silica shells has been tuned from 20 to 50 nm while the zeolite A particle size changes from nanometer to micrometer. Pores of the silica shells arranged orderly on the crystal-faces of zeolite-A cores. Typically, adsorption amount of the butyraldehyde towards these core–shell composite materials is investigated well and is verified to be almost double than that of the pristine zeolite A. Interestingly the nano-zeolite A core containing core–shell composite absorbs maximum butyraldehyde (314 mg/g) compared to the micro-zeolite A (266 mg/g), even if the mesoporous shell thickness of the nano-zeolite A@SiO2 composites is less (20 nm) than that of micro-zeolite A@SiO2 (50 nm). Both of these values are significantly larger than the pristine zeolite A (nano-zeolite A; 151 mg/g and micro-zeolite A; 146 mg/g).