Encapsulation of Keggin-type manganese-polyoxomolybdates in MIL-100 (Fe) for efficient reduction of p-nitrophenol

Confining polyoxometalates inside the cavities of metal-organic frameworks is a method to utilize these versatile molecular metal oxide clusters as quasi-heterogeneous catalysts and to thereby broaden their applications. In this study, manganese-polyoxomolybdate anions of the Keggin structure type, [P^VMo^VI₁₁Mn^II(H₂O)O₃₉]^5- (Mn-POM), are encapsulated in an iron(III)-based metal-organic framework (MIL-100) to achieve 30 wt.-% loaded Mn-POM/MIL-100 composite material (1). The composite compound 1 displays excellent catalytic activity for the selective reduction of p-nitrophenol into p-aminophenol (96%) at 20 °C in 25 min. The rate constant and catalyst activity are calculated as 0.10 min^-1 and 328 L g^-1 s^-1, respectively. Interestingly, both individual components of the composite material are themselves inactive toward this reaction.