Room-temperature fabrication of core-shell nano-ZnO/pollen grain biocomposite for adsorptive removal of organic dye from water

•Meso-/macro-porous nano-ZnO covered pollen grains are prepared at room temperature.•A possible formation mechanism of the core-shell microparticles was proposed.•Adsorptive removal of Malachite Green from water by the biocomposite is studied.