Dual‐Induced Confined Synthesis of Metastable γ‐MnO ₂ Nanoclusters in Metal–Organic Frameworks for Highly Efficient Ozone Decomposition

Abstract 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‐MnO 2 was stabilized and confined within MIL‐101(Fe) for the first time. The optimized 15% γ‐MnO 2 @MIL‐101(Fe) showed a durable 100% O 3 removal efficiency for over 100 h. This performance was maintained in a continuous air flow containing 40 ppm O 3 at a high gas hourly space velocity of 1.7 × 10 5 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‐MnO 2 active sites and the Fe 3 O 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.