Gel-like ZnO/Zr-MOF(bpy) nanocomposite for highly efficient adsorption of Rhodamine B dye from aqueous solution

A highly efficient Rhodamine B (RhB) adsorbent based on a gel-like ZnO/Zr-metal-organic framework (ZnO/Zr-MOF) composite was prepared by reacting ZnO nanopartides with glacial-acetic-acid-modulated Zr-MOF(bpy) via a sample solvothermal method. Introduction of ZnO greatly improved the texture properties of the parent Zr-MOF(bpy), and the resulting material exhibited an agglomerate morphology consisting of numerous quadrate nanoparticles, which is quite different from the cubo-polyhedron morphology of Zr-MOF(bpy). In this way, this composite showed a considerable RhB absorption capacity from aqueous solution in a wide pH range. The adsorption kinetics, isotherms and thermodynamics of the RhB adsorption by ZnO/Zr-MOF(bpy) were discussed and confirmed that this adsorption process satisfied pseudo-second-order kinetics and the Langmuir model, and was a spontaneous exothermic process. Moreover, the excellent adsorption performance is likely related to the synergism of hydrogen bonding, electrostatic interactions and pi-pi interactions between the ZnO/Zr-MOF(bpy) nanocomposite and RhB. The excellent texture properties of ZnO/Zr-MOF(bpy) promote the adsorption and diffusion of RhB on it, which is also crucial during the adsorption process.