Breaking the Diffusion-Dispersion Trade-Off: Subnanometric MoO₃ Clusters in Interzeolite Transformation Intermediates...

Overcoming the intractable trade-off between restricted bulky molecule diffusion in microporous zeolites and poor active-metal dispersion on mesoporous supports remains a formidable challenge, particularly in the deep oxidative desulfurization of fuel oils. Herein, by strategically trapping metastable amorphous protozeolites during the interzeolite transformation of FAU to Beta zeolite, we engineered a Mo-functionalized interzeolite transformation intermediate (Mo-AZ) featuring abundant silanol defects and a well-established mesoporous architecture. These silanols serve as robust anchoring sites, yielding a unique (Si─O─)₁Mo(─O─Mo)₅ interfacial coordination that firmly stabilizes MoO₃ species as sub-nanometric clusters (∼1.27 nm). Crucially, the hierarchical mesoporous network eradicates the spatial steric hindrance for bulky sulfur substrates, while the highly hydrophilic silanol microenvironment not only specifically enriches the oxidant of hydrogen peroxide but dynamically promotes its spontaneous cleavage into ultra-reactive superoxide radicals. Consequently, Mo-AZ exhibits exceptional catalytic activity and robust structural stability for deep oxidative desulfurization. This work decisively dismantles the mass-transfer barriers in the catalytic conversion of bulky molecules, pioneering a novel paradigm for designing high-performance sub-nanocluster catalysts via the defect engineering of metastable protozeolites.