Host–guest synthesis and encapsulation of phosphotungstic acid in MIL-101 via “bottle around ship”: An effective catalyst for oxidative desulfurization

Successful encapsulation of phosphotungstic acid (PTA) within the nanocages of MIL-101 has been achieved via “bottle around ship” approach under static condition. XRD, FT-IR, 31P MAS NMR, N2 adsorption, SEM–EDS and XRF confirm the incorporation and well-distribution of PTA in both middle and large cavities of the MIL-101. SEM, XRD and TEM reveal the dominant crystal shapes of high loading PTA@MIL-101 are a monolithic and the adjacent lattice planes of MIL-101 are larger due to the addition of PTA. The host–guest composite materials PTA@MIL-101 containing 17–50 wt.% of PTA have been obtained and demonstrate an excellent catalytic performance in the oxidative desulfurization process of the refractory sulfur-containing compounds. This is the first example of the application of MIL-101 or PTA@MIL-101 composite materials in oxidative desulfurization. The reactivity of the sulfur-containing compounds follows the order DBT > 4,6-DMDBT > BT. In four consecutive reaction cycles, the catalyst recovery is in excess of 71%, while the DBT conversion slightly decreases.

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► The well-dispersed PTA in both medium and large cavities of MIL-101.
► About three Keggin polyanions are allocated to per cavity of MIL-101.
► The adjacent lattice planes of MIL-101 are larger due to the addition of PTA.
► The dominant crystal shapes of high loading PTA@MIL-101 are a monolithic.
► The reactivity of ODS follows the order DBT > 4,6-DMDBT > BT using PTA@MIL-101.