Selective oxidation catalysts obtained by immobilization of iron(III) porphyrins on thiosalicylic acid-modified Mg-Al layered double hydroxides.
Nitrate-intercalated Mg-Al layered double hydroxides (LDHs) were synthesized and exfoliated in formamide. Reaction of the single layer suspension with thiosalicylic acid under different conditions afforded two types of solids: LDHA1, in which the outer surface was modified with the anion thiosalicylate, and LDHA2, which contained the anion thiosalicylate intercalated between the LDH layers. LDHA1 and LDHA2 were used as supports to immobilize neutral (FeP1 and FeP2) and anionic (FeP3) iron(III) porphyrins. For comparison purposes, the iron(III) porphyrins (FePs) were also immobilized on LDH intercalated with nitrate anions obtained by the co-precipitation method. Chemical modification of LDH facilitated immobilization of the FePs through interaction of the functionalizing groups in LDH with the peripheral substituents on the porphyrin ring. The resulting FePx-LDHAy solids were characterized by X-ray diffraction (powder) and UV-Vis and EPR spectroscopies and were investigated as catalysts in the oxidation of cyclooctene and cyclohexane. The immobilized neutral FePs and their homogeneous counterparts gave similar product yields in the oxidation of cyclooctene, suggesting that immobilization of the FePs on the thiosalicylate-modified LDHs only supported the catalyst species without interfering in the catalytic outcome. On the other hand, in the oxidation of cyclohexane, the thiosalicylate anions on the outer surface of LDHA1 or intercalated between the LDHA2 layers influenced the catalytic activity of FePx-LDHAy, leading to different efficiency and selectivity results. FeP1-LDHA2 performed the best (29.6% alcohol yield) due to changes in the polarity of the surface of the support and the presence of FeP1. Interestingly, FeP1 also performed better in solution as compared to the other FePs. Finally, it was possible to recycle FeP1-LDHA2 at least three times.
Laboratório de Química Bioinorgânica e Catálise, Departamento de Química, Universidade Federal do Paraná (UFPR), CP 19081, CEP 81531-990 Curitiba, Paraná, Brazil.
Kelly Aparecida Dias
KA
de Freitas Castro
Laboratório de Química do Estado Sólido, Centro de Pesquisas em Química Aplicada (CEPESQ), Departamento de Química, Universidade Federal do Paraná (UFPR), CP 19081, CEP 81531-990 Curitiba, Paraná, Brazil.
Fernando
F
Wypych
Laboratório de Química Bioinorgânica e Catálise, Departamento de Química, Universidade Federal do Paraná (UFPR), CP 19081, CEP 81531-990 Curitiba, Paraná, Brazil.
Ariana
A
Antonangelo
Laboratório de Química Bioinorgânica e Catálise, Departamento de Química, Universidade Federal do Paraná (UFPR), CP 19081, CEP 81531-990 Curitiba, Paraná, Brazil.
Karen Mary
KM
Mantovani
Laboratório de Catálise e Energias Renováveis, Universidade Tecnológica Federal do Paraná, Medianeira, Paraná, Brazil.
Alesandro
A
Bail
Laboratório de Química Bioinorgânica e Catálise, Departamento de Química, Universidade Federal do Paraná (UFPR), CP 19081, CEP 81531-990 Curitiba, Paraná, Brazil.
Geani Maria
GM
Ucoski
Universidade de Franca, Departamento de Química, Franca, São Paulo, Brazil.
Kátia Jorge
KJ
Ciuffi
Universidade de Franca, Departamento de Química, Franca, São Paulo, Brazil.
Thais Elita
TE
Cintra
Laboratório de Química Bioinorgânica e Catálise, Departamento de Química, Universidade Federal do Paraná (UFPR), CP 19081, CEP 81531-990 Curitiba, Paraná, Brazil. Electronic address: shirleyn@ufpr.br.
Shirley
S
Nakagaki
Heterogeneous catalysis; Immobilization; Layered double hydroxide; Oxidation; Porphyrin