Carbonizing hollow metal–organic framework/layered double hydroxide (MOF/LDH) nanocomposite with excellent adsorption capacity for removal of Pb(II) and organic dyes from wastewater

Abstract A novel sorbent ZIF-67/LDH@C was synthesised using mild etching and co-precipitation and carbonization calcination for the elimination of lead ions (Pb 2+ ), malachite green (MG), and congo red (CR) from water. The three-dimensional hollow MOF structure and two-dimensional LDH nanosized layers of ZIF-67/LDH@C were demonstrated by scanning electron microscope (SEM), transmission electron microscopy (TEM), fourier transform infrared (FT-IR), X-ray diffraction (XRD), nitrogen adsorption/desorption, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) characterization. The maximal adsorption capability of Pb 2+ , MG, and CR could reach 662.25, 1729.83 and 526.32 mg∙g −1 , respectively. The kinetic study proved that the adsorption was chemisorption or strong complexation and the rate-limiting step was intraparticle diffusion. The isotherms effectively indicated the monomolecular-type adsorption. Thermodynamic studies showed the spontaneous and endothermic nature of Pb 2+ , MG and CR adsorption onto ZIF-67/LDH@C. The adsorption mechanisms of ZIF-67/LDH@C may be attributed to electrostatic attraction, π-π interaction, hydrogen-bonding interaction, and surface complexation between ZIF-67/LDH@C and pollutants. Furthermore, favourable stability and negligible interference from other metal ions could promote the viability of the practical application of ZIF-67/LDH@C in wastewater purification. Graphical Abstract