Nonclassical growth to mesoporous quasi-single crystal CeO₂ superstructures with a well-defined surface

Single-crystal materials are essential for fundamental catalysis studies and advanced technologies; however, synthesizing single crystals that simultaneously integrate mesoporosity, tunable size, and well-defined surfaces remains challenging. Here, we report a wet-chemical, template-free strategy to synthesize mesoporous quasi-single-crystal CeO₂ superparticles (SPs). Operando wide- and small-angle X-ray scattering combined with theoretical modeling reveal a nonclassical growth mechanism driven by the oriented attachment of nanocluster building blocks. This process yields high-surface-area quasi-single crystals that preferentially expose energetically favorable (111) facets on both the external surfaces and internal pore walls, thereby enhancing the stabilization of active sites when used as heterogeneous catalyst supports. Using this approach, we demonstrate broad applicability by synthesizing highly dispersed precious metal-loaded CeO₂ (M/CeO₂, M = Pd, Pt, Rh, or Ir) and metal-doped CeO₂ (Cu-CeO₂) SPs. Moreover, Pd/CeO₂ SPs exhibit effective stabilization of Pd clusters in CO₂ hydrogenation to methanol, delivering a high methanol selectivity of 85% and markedly improved durability compared with conventional supports.