Formation, Phase Transition, Surface, and Catalytic Properties of Cubic ZrO ₂ Nanocrystals

ZrO2 is a relevant industrial and technological material with structure-dependent properties. The high-temperature tetragonal and cubic phases can be stabilized at room temperature through the incorporation of stabilizing cations. Tetragonal pure ZrO2 can additionally be stabilized by reducing the crystallite size to the nanoscale; however, stabilizing cubic pure ZrO2 at room temperature remains challenging. Here, cubic ZrO2 nanocrystals are synthesized by reacting a low concentration of ZrCl4 (0.025 mol L–1) with acetophenone. Pair distribution function and extended X-ray absorption fine structure analyses reveal that the local structure around the zirconium atoms is highly distorted relative to that of the ideal cubic. The structure can be modified by increasing the precursor concentration (up to 0.1 mol L–1), eventually leading to the formation of entirely monoclinic nanocrystals. The surface properties and catalytic behavior of cubic ZrO2 are investigated for establishing structure–property correlations and comparisons with the monoclinic phase. An optimized combination of activity, product yields, and recyclability in the multistep conversion of α-angelica lactone to γ-valerolactone is achieved with small cubic ZrO2 particles of 2.3 ± 0.4 nm size. Our results provide insights into the stabilization of cubic ZrO2 and phase transitions at room temperature and demonstrate the potential of cubic-type pure ZrO2 for catalytic applications.