Synthesis of Metal Salen@MOFs and Their Catalytic Performance for Styrene Oxidation

A series of effective heterogeneous catalysts, Cu or Ni salen with various loadings encapsulated in amino functionalized MOFs, were synthesized successfully for the first time via a one-pot method and denoted as metal salen@NH2-MIL-101(Cr). On the basis of detailed characterization of the catalysts, the varying coordination abilities between the Cu or Ni salen and NH2-MIL-101(Cr) provided the as-prepared Cu or Ni salen@NH2-MIL-101(Cr) with distinct activities toward styrene oxidation. The catalytic results showed that the introduction of Cu or Ni salen can significantly promote the selectivity to epoxide. However, Cu salen@NH2-MIL-101(Cr) showed preferable activity for styrene oxidation, and phenylacetaldehyde was generated with increasing Cu salen content. The optimal conditions for the reaction were also discussed, including the types of oxidants present, molar ratios of styrene and TBHP, and temperature. In particular, the mechanism of the styrene oxidation in 70% TBHP over Cu salen@NH2-MIL-101(Cr) was proposed in this work.