Design of a cage–core–chain structure catalyst for deep catalytic oxidative desulfurization with enhanced substrate enrichment†

Developing composite metal–organic framework (MOF) catalysts that integrate target molecule enrichment and reactive oxygen species generation to enhance oil–water biphasic desulfurization efficiency remains challenging. A “cage–core–chain” structured functional catalyst, [Bmim]PW@MIL-101(Fe), was designed by encapsulating a phosphotungstic acid (HPW) core inside an MIL-101(Fe) cage and grafting [Bmim]⁺ chains (hydrophobic ionic liquid groups) onto it. The W–O–Fe bond facilitates electron transfer, redistributes charge density, and activates peracetic acid. The Fe³⁺/Fe²⁺ redox cycle promotes the generation and transformation of reactive oxygen species, with singlet oxygen (¹O₂) as the primary oxidant. Density functional theory (DFT) calculations confirm charge density changes between core and shell, and active oxygen generation pathways. Additionally, the catalyst creates a micro-oil environment at the solid–oil–water interface, enhancing the enrichment of dibenzothiophene (DBT) and its interaction with reactive oxygen species, achieving nearly 3.5 times the DBT removal efficiency of MIL-101(Fe). This work provides a sustainable strategy for activating catalytic sites in MOFs with inherently low activity, offering an efficient desulfurization approach for cleaner fuel production.