Cu(II), Co(II), Fe(III) or VO(II) Schiff base complexes immobilized onto CMK-3 for styrene epoxidation

• Cu(II), Co(II), Fe(III) or VO(II) Schiff base complexes were covalently attached on amino-modified CMK-3-O.
• The catalysts were characterized by XRD, FT-IR, SEM, TEM, TG, Raman, BET, XPS and ICP-AES.
• The catalysts were active and showed good recoverability in the epoxidation of styrene.

Schiff base complexes containing transition metals (Cu, Co, Fe or V) were successfully immobilized onto amino-functionalized CMK-3 via a stepwise procedure as heterogeneous catalysts for styrene epoxidation. The materials were characterized by means of XRD, N2 adsorption/desorption, TEM, SEM, FT-IR, Raman, XPS, TG. and ICP-AES. The results of XRD, N2 adsorption–desorption and TEM revealed that the structure of CMK-3 was well preserved, while the results of FT-IR, TG, Raman, XPS and ICP-AES suggested that the Cu(II), Co(II), Fe(III) or VO(II) Schiff base complexes have been successfully incorporated onto amino-modified CMK-3. Catalytic results showed that high conversion of styrene (94.1%) and selectivity to styrene oxide (73.9%) can be achieved over the heterogeneous Co (II) catalyst with air as the oxidant and isobutyraldehyde as co-reductant. In addition, the functionalized CMK-3 catalyst was quite stable and could be recycled at least three times.

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