Novel fabrication of rod-like CoAl2O4/halloysite hybrid pigment derived from Co-MOF/nano-clay and mechanism exploration

In this work, we successfully report the design and synthesis of rod-like CoAl 2 O 4 /halloysite hybrid pigment from zeolitic imidazolate framework-67 (ZIF-67, a Co-based MOF) and tubular halloysite via a facile two-step route for the first time. The as-prepared nanostructures were thoroughly characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared reflection (FTIR Spectroscopy), thermogravimetric and differential scanning calorimetry (TG-DSC), X-ray photoelectron spectrometer (XPS), ultraviolet–visible spectrometry (UV–vis) and CIE L* a* b* colorimetric method . XRD patterns indicated that the presence of CoAl 2 O 4 spinel was observed at various temperatures ranging from 800 to 1100 °C. The SEM and TEM images showed that the nano-pigment has a rod-like hybrid structure composed of nano CoAl 2 O 4 particles and SiO 2 . The color performance of the fabricated pigments was evaluated and given suitable color coordinates (L* = 44.72, a* = −14.40, b* = −37.83) and (L* = 42.57, a* = −7.68, b* = −41.14) at the calcination temperature of 1100 °C for 2 h and 3 h, respectively. The mechanism study indicated that these composites were formed by Co 3 O 4 derived of ZIF-67 as highly active cobalt source and Al 2 O 3 decomposed from halloysite substrate as aluminum source. In addition, the corrosion resistance test showed that the CoAl 2 O 4 composites retain crystalline stability, almost no color deviation in CIE chromatic system even after 1 M HCl leaching. Furthermore, the CoAl 2 O 4 /halloysite exhibited excellent thermal and suspension stability, which indicated it could be a promising candidate for ceramic glazes and water-borne coatings. These findings provide insight into a new strategy for the synthesis of clay mineral-based ceramic pigment .