Crystalline ZrO2 Monoliths with Well-Defined Macropores and Mesostructured Skeletons Prepared by Combining the Alkoxy-Derived Sol–Gel Process Accompanied by Phase Separation and the Solvothermal Process

We have successfully prepared multiscale porous crystalline zirconia (ZrO 2 ) monoliths by combining the alkoxy-derived sol–gel process accompanied by phase-separation and the solvothermal process. The gelation can be controlled by the addition of N -methylformamide to the starting solution, while the phase separation is induced by the incorporation of poly(ethylene oxide). Amorphous ZrO 2 monolithic gels with well-defined bicontinuous macropores and microstructured skeletons are obtained when the transient structure of polymerization-induced phase separation is fixed by the gelation. The size of the macropores is controlled in the range of 300 nm to 2 µm by adjusting the amount of poly(ethylene oxide). The solvent exchange of the mother liquor in the as-gelled wet specimens with absolute ethanol, followed by the solvothermal treatment at temperatures above 210 °C, brings about the formation of mesopores and stabilizes tetragonal ZrO 2 nanocrystals without disturbing the macroporous morphology. The resultant macro-mesoporous crystalline ZrO 2 gels possess the surface area over 200 m 2 g −1 .