Dual-Induced Confined Synthesis of Metastable γ-MnO₂ Nanoclusters in Metal-Organic Frameworks for Highly Efficient...

Ultrafine metal oxide nanoclusters (UMONs) exhibit remarkable catalytic potential due to their high specific surface area; however, achieving precise control over both the size and crystal phase of UMONs remains a significant challenge. Herein, we developed a dual-induced confined synthesis strategy that couples hydrophobic gating with thermally triggered phase transformation to precisely confine UMONs within the pores of a metal-organic framework (MOF). 13 UMONs@MOF composites were successfully synthesized with the metal cations in UMONs spanning different regions of the periodic table. Notably, sub-3 nm metastable γ-MnO₂ was stabilized and confined within MIL-101(Fe) for the first time. The optimized 15% γ-MnO₂@MIL-101(Fe) showed a durable 100% O₃ removal efficiency for over 100 h. This performance was maintained in a continuous air flow containing 40 ppm O₃ at a high gas hourly space velocity of 1.7 × 10⁵ h^-1 over a wide humidity range of 10%-90%. Mechanistic studies reveal that its superior catalytic activity originates from the synergistic effect between the confined γ-MnO₂ active sites and the Fe₃O clusters in the MIL-101(Fe). This work provides a universal approach for the precise control of the size and crystal phase of UMONs, paving the way for designing high-performance catalysts.