Immobilization of ruthenium schiff base complex in the metal-organic framework UiO-67

Zirconium-based metal-organic framework, UiO-67, was synthesized and used as support for the immobilization of the [RuCl₂(ENAPY)] (ENAPY = N,N'-bis(7-methyl-2-pyridylmethylene)-1,2-diiminoethane)). The immobilized system exhibited violet blue color. The {UiO-67/[RuCl₂(ENAPY)]} was characterized by cyclic voltammetry, X-ray diffraction, UV-Vis, FTIR and X-ray photoelectron spectroscopy. The electrochemistry of the immobilized system is characterized by a reversible pair of waves at +0.40 V (vs NHE), ascribed to the Ru^3+/2+ redox process. The electronic spectrum of the immobilized system is characterized by bands at 520 and 380 nm ascribed to a ligand-to-metal charge-transfer transitions {Ru²⁺(d_π) → ENAPY(p_π*)}. The IR bands of immobilized complex {1630 cm^-1 (ν_asC=C), 1590 cm^-1 (ν_asC=N), 1450 cm^-1 (ν_sC=C), 1340 cm^-1 (ν_sC=C)} are weak in comparison with the neat complex due to their low concentration in MOF cages. X-ray diffractogram of the immobilized system indicated that the crystallinity and morphology of UiO-67 was preserved during inclusion of ruthenium complex. The XPS spectra of UiO-67 and UiO-67/ruthenium complex shows a signal at 462 eV that can be ascribed to Ru 3p^3/2 and at 400 eV ascribed to N 1s core level of the ruthenium Schiff base complex immobilized into MOF. (author)