One-step in situ preparation of Zr(Ti)-MOFs on titanium alloys at a low temperature of 80 °C and atmospheric pressure

Preparing metal-organic frameworks (MOFs) film in situ on the surface of the Ti-6Al-4V (TC4) titanium alloy is challenging owing to the dense and stable surface TiO2 passive film. In this study, titanium-doped zirconium-based MOFs (Zr(Ti)-MOFs) film was constructed in situ on the TC4 alloy in one step at a low temperature and atmospheric pressure, with ZrCl4 as the source of Zr metal ions. ZrCl4 attacked and dissolved the TiO2 film to form Zr-O-Ti bonds on the surface of TC4 to provide nucleation sites for further reactions. At the same time, Zr4+ and dissolved Ti4+ combined in solution to form Ti containing Zr-O cluster nodes, which aggregated and grafted to the Zr-O-Ti bonds on the substrate surface, and reacted with organic ligands (terephthalic acid) to form Zr(Ti)-MOFs film. The Ti4+ dissolved from the TC4 participate in the Zr-MOFs formation, thereby changing the high temperature and high-pressure conditions required for the traditional preparation of Zr-MOFs (UiO-66). The in situ preparation of Zr(Ti)-MOFs on TC4 was achieved at 80°C under atmospheric pressure conditions. This study elucidated the growth mechanism of Zr(Ti)-MOFs on the TC4 surface, providing a reference for the design and in-situ preparation of multifunctional MOFs on the TC4 titanium alloy.