In summary, we have successfully fabricated high-performance porous ceramics 9PHEBs with superior mechanical and thermal properties via a simple and effective UHTS technique. The combination of a high mechanical strength (≈337 MPa) at a porosity of ≈50% and a low thermal conductivity (≈0.76 W m−1 K−1) endows our 9PHEB materials with great potential as reliable thermal insulation. The superior mechanical and thermal properties are believed to result from the multiscale design: i) the ultrafine pores at the microscale, as well as strong connections and good interfaces between building blocks at the nanoscale, can be well constructed, owing to the ultrafast heating rate and ultrahigh temperature of the UHTS technique; ii) the severe fluctuations of the mass and strain fields induced by the large lattice distortion at the atomic scale, which simultaneously improves the stiffness of lattice and decreases the thermal conductivity of the ceramics by acting as phonon scattering barriers. Moreover, the synthesized 9PHEB show exceptional dimension and strength retention up to 2000 °C, making them suitable for use in extreme conditions.