Dense and homogeneous coatings of CPO-27-M type metal-organic frameworks on alumina substrates

The deposition of five isostructural PCPs from the CPO-27-M (M = Ni, Co, Mg, Zn and Mn) family on top of amorphous Al₂O₃ was studied. The coatings were grown directly out of solvothermal mother solutions prepared following published procedures. Powder X-ray diffraction and scanning electron microscopy studies showed that when enough surface binding sites are available, continuous and uniform coatings of phase-pure CPO-27-Ni, Co and Mg are obtained. In the case of CPO-27-Zn and Mn, large crystals are spread onto the surface in a non-continuous fashion. The different morphologies suggest a strong effect of the cation nature on the growth mechanism and binding to the substrate. Activation and loading experiments were also performed in order to check the porosity of the films.