MOF-Derived SiO2 Confinement Strategy for Regenerable CrOx Catalysts in Moderate-Temperature Chemical Looping Oxidative Dehydrogenation of Ethylbenzene

High-loading chromium oxide catalysts are attractive for the dehydrogenation of ethylbenzene (EB) to styrene (ST), but the migration, aggregation, and irreversible restructuring of Cr species during high-temperature calcination and reaction often reduce active-site accessibility and accelerate catalyst deactivation. Herein, we report a reverse double-solvent strategy to construct a shape-preserving mesoporous SiO 2 framework within a Cr-MOF precursor, yielding a Cr@Si-6 catalyst in which Cr 3+ -rich nanoscale Cr 2 O 3 domains and highly dispersed chromate-like Cr 6+ species are stabilized within a silica cage-like network. This architecture integrates three complementary structural features: the homogeneous Cr distribution inherited from the MOF precursor, physical confinement by the mesoporous SiO 2 framework, and chemical anchoring with electronic regulation through Cr–O–Si interfacial linkages, thereby reconciling high Cr loading with high dispersion. Structural and spectroscopic characterizations show that the SiO 2 skeleton suppresses long-range Cr migration, aggregation, and the development of bulk-like Cr 2 O 3 domains, while Cr–O–Si interfacial coupling regulates the local coordination and electronic environment of the Cr species and strengthens their resistance to reduction-induced restructuring. In the chemical looping oxidative dehydrogenation of ethylbenzene (EB-CL-ODH), lattice oxygen participates in EB conversion during the reduction step, followed by regeneration of the reduced catalyst in a separate O 2 oxidation step. Cr@Si-6 achieves 80% EB conversion, 91% ST selectivity, and 73% ST yield at the moderate temperature of 450 ° C, outperforming directly calcined Cr-MOF-600 and conventional Cr/SiO 2 , while maintaining an ST selectivity above 90% with no obvious decay in EB conversion over 40 redox cycles. Postreaction XRD, Raman, TG/DTG, GC–MS/TIC, and SEM/EDS analyses further show that the confined Cr 2 O 3 /SiO 2 architecture is largely preserved and that reaction-induced carbonaceous and heavy organic deposits can be substantially removed through oxidative regeneration. This work demonstrates that integrating MOF-derived Cr distribution, mesoporous silica confinement, and Cr–O–Si interfacial regulation provides an effective strategy for constructing high-loading, highly dispersed, and regenerable Cr-based oxygen carriers for moderate-temperature EB-CL-ODH.