The encapsulation of POM clusters into MIL-101(Cr) at molecular level: LaW10O36@MIL-101(Cr), an efficient catalyst for oxidative desulfurization

Abstract

The anchoring of Weakley-type polyoxometalate (POM) Na 7 [H 2 LaW 10 O 36 ] in mesoporous metal-organic framework (MOF) MIL-101(Cr) to prepare a novel host-guest composite is here reported for the first time. The successful encapsulation of LaW 10 into MIL-101(Cr) has been achieved via facile tandem post-synthetic modification strategy and confirmed by several instrumental techniques. The LaW 10 guests were dispersed homogeneously in MIL-101(Cr) nanocages at molecular level. The as-synthesized composite combines both the merits of the POMs (remarkable efficiency and reversible redox) and MOF (sufficient recyclability and exceptional porosity), thus displaying obvious host-guest synergistic effect. The LaW 10 O 36 @MIL-101(Cr) composite served as heterogeneous single-site catalyst for ODS process and exhibited excellent catalytic performance, with removal efficiency of 99.1, 94.5 and 84.7% for DBT, 4,6-DMDBT and BT, respectively. Thanks to the confinement effect from Cr···O W coordinative interaction, the catalyst provided outstanding recyclability and stability, and can be reused for seven times without leaching, structural alteration and deactivation. Moreover, the structure-activity relationship was investigated in detail, as well as the proposed mechanism. • The Weakley structure POMs were encapsulated into MIL-101(Cr) for the first time. • The LaW 10 O 36 were dispersed uniformly within MIL-101(Cr) at molecular level. • The host-guest synergistic effect enhanced remarkably ODS efficiency and durability. • The confinement effect of MIL-101(Cr) on LaW 10 O 36 results in excellent ODS recyclability.