Influence of thermal treatment on the structure and adsorption properties of layered zinc hydroxychloride

Abstract Layered zinc hydroxychloride (Zn 5 (OH) 8 Cl 2 ·H 2 O) synthesized by hydrolyzing the ZnO particles in aqueous ZnCl 2 solutions at 100 °C for 48 h was outgassed at different temperatures ranging from 100 to 250 °C for 2 h and the structure and adsorption properties of the products were examined by various means. Outgassing at 100–150 °C eliminated the H 2 O molecules in interlayer of zinc hydroxychloride. The layered structure of zinc hydroxychloride was disintegrated at 175 °C by breaking the OH⋯Cl hydrogen-bond in interlayer to form curled thin films composed of poorly crystallized β-Zn(OH)Cl and ZnO, leading to the increment of the specific surface area from 4 to 39 m 2 /g. The β-Zn(OH)Cl was decomposed at 225 °C to form ZnO. The crystallinity of ZnO was increased on elevating the outgassing temperature, giving rise to the UV absorption property. The H 2 O and CO 2 adsorption measurements revealed that the zinc hydroxychloride outgassed at 100–150 °C possessed a high H 2 O and CO 2 adsorption selectivity, and the selectivity diminished by the formation of thin films of ZnO above 175 °C.