Polyoxometalate immobilized in MIL-101(Cr) as an efficient catalyst for water oxidation

• Polyoxometalate (CoPOM) is immobilized in cavities of MIL-101(Cr) with a good dispersion by a facile ion exchange method.
• Immobilized CoPOM exhibits enhanced photocatalytic and electrocatalytic water oxidation activities and improved stability due to its interaction wit MIL-101.
• Heterogenization of homogeneous CoPOM makes it easier to be recycled.

Water oxidation is an essential reaction in artificial photosynthesis. Finding efficient and stable catalysts for this reaction is still a challenging task. Recently, a series of polyoxometalates (POMs) comprised of earth abundant materials are reported to be efficient water oxidation catalysts (WOCs). In this study, we investigated the effect of a support material to the catalytic performance of [Co(H2O)2(PW9O34)2]10− (CoPOM) by immobilizing this molecular POM-based catalyst on MIL-101(Cr), a highly porous and robust metal-organic framework (MOF). The successful encapsulation of CoPOM in MIL-101 achieved by a facile ion exchange method was evidenced by combined XRD, FTIR, XPS, XANES, TEM and elemental mapping analyses. Both the photocatalytic and electrochemical studies have indicated that the CoPOM loaded on MIL-101 displays enhanced activity and improved stability due to the its electrostatic interaction with MIL-101. In addition, the heterogenization of the homogeneous CoPOM also makes it easier to be recycled.

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