A water-stable functionalized NiCo-LDH/MOF nanocomposite: green synthesis, characterization, and its environmental application for heavy metals adsorption

Abstract Removal of toxic heavy metals from aquatic environments has become a major concern due to environmental problems and the potential hazards and risks posed by them. Nowadays, the adsorption method as one of the most effective methods of removing pollutants has attracted increasing attention among chemists and environmental researchers. However, one of the challenges is to design and develop more effective adsorbents as well as to prepare them via greener and safer approaches. In line with these goals, a functionalized Ni50Co50-layered double hydroxide/UiO-66-(Zr)-(COOH)2 nanocomposite (LDH/MOF NC) was prepared via a facile and “green“ synthesis protocol and used as an effective adsorbent for removal of mercury and nickel cations from aqueous media. UiO-66-(Zr)-(COOH)2 nanoparticles were in situ grown homogeneously over the surface of the functionalized two-dimensional ultrathin Ni50Co50-LDH sheets. A green organic-solvent-free route was used to prepare the LDH/MOF NC in which the water is used as a green solvent. The adsorption performance of LDH/MOF NC for removal of Hg(II) and Ni(II) cations was studied and the influence of some experimental factors, such as solution pH, initial metal concentration, and contact time, on the adsorption process were investigated. The theoretical maximum adsorption capacities based on the Langmuir isotherm were found to be 509.8 mg g−1 and 441.0 mg g−1 for Hg(II) and Ni(II), respectively, under constant conditions. We believe that the facile and “green” synthesis method used in this work can be a starting point for the fabrication and development of similar composite materials for future works, especially for use in adsorption, extraction, catalysis, and drug delivery applications.