Molecules 2020, 25, 2389
10 of 12
3
. Materials and Methods
3
.1. Materials
Manganese(II) chloride tetrahydrate, cupric nitrate trihydrate, sodium bicarbonate, styrene,
hydrogen peroxide, N,N-Dimethyl formamide (DMF), acetonitrile, 1,4-Dioxane, tetrahydrofuran (THF),
,2-dichlorethane (1,2-DCE), toluene, ethanol, and methanol were purchased from Jinshan Chemical
1
Company(Chengdu, China), 2,5-dihydroxyterephthalic acid (H DHTA), 2-picolinic acid (PCA),
4
m-chloroperoxybenzoic acid (m-CPBA), tert-butyl hydroperoxide (TBHP), and iodosylbenzene (PhIO)
were purchased from Adamas Regent Company. All the chemicals were analytical grade and purchased
from commercial sources and used without further purification.
3
.2. Preparations of Mn-MOF, Cu-MOF, and MnxCuy-MOF
The Mn-MOF was synthesized as follows: MnCl2 4H O (0.757 mmol), H DHTA (0.126 mmol)
·
2
4
and PCA (0.126 mmol) were dissolved in 17 mL DMF containing 1 mL of ethanol and 1 mL of H O.
Subsequently, the solution was moved into 25 mL teflon-lined autoclave and heated at 120 C for 24 h.
2
◦
After cooling to room temperature, the product was collected by centrifugation and washed three
times with DMF and CH OH, respectively. Finally, the crystallized Mn-MOF of 119 mg was obtained
3
through drying in a vacuum for 12 h. By the similar procedures, the Cu-MOF and Mn
with various molar ratio of Mn to total metal were obtained.
x
Cu1 -MOF
−x
3
.3. Epoxidation of Olefin
The typical catalytic reaction was carried out as follows: 1 mmol styrene and 6 mg MOFs were
added to a 25 mL round bottom flask containing 2 mL DMF. Then, the solution was dripped into 0.9 M
6
0
7 µL NaHCO aqueous solution containing 612 µL H O of 30% (w/w). The solution was kept at
3 2 2
C in an ice bath and stirred continuously for 6 h. The concentrations of reaction substrates and
◦
products were determined by GC through the comparison of the peak area of analyte with that of
internal standard.
4
. Conclusions
In this work, we prepared a series of bimetallic organic framework Mn
by hydrothermal synthesis. The MOFs was characterized and analyzed by PXRD, XPS, SEM, and TEM.
The Cu–MOF showed low catalytic activity for both epoxidation of olefins and decomposition of H O ,
x
Cu1 -MOF with two ligands
−x
2
2
while Mn-MOF showed good catalytic activity for both. The Mn0.1Cu0.9-MOF exhibits excellent catalytic
activity for the epoxidations of various aromatic and cyclic olefins and weak activity on decomposition of
H O . Styrene can be oxidized by H O and the yield of styrene oxide achieves 85% in the presence of
2
2
2
2
◦
Mn Cu -MOF at 0 C after reaction 6 h. The decomposition of H O catalyzed by Mn Cu -MOF
0
.1
0.9
2
2
0.1
0.9
◦
was 4.0% after reacting 6 h at 0 C. The inverse temperature effect in catalytic epoxidation reaction was
discussed. A mechanism of peroxybicarbonate-assisted catalysis was suggested. The catalyst can be
reused at least five cycles without significant loss in activity towards epoxidation. The conversion of
styrene reached 87.8% and the selectivity of styrene oxide kept still 86.4% after five cycles.
Supplementary Materials: Supplementary Materials are available online.
Author Contributions: Conceptualization, F.W. and X.-G.M.; methodology, F.W. and X.-G.M.; formal analysis,
F.W., Y.-Y.W. and H.H.; investigation, F.W., W.-W.Y. and X.-G.M.; resources, Y.-Y.W.; data curation, F.W. and
X.-G.M.; writing—original draft preparation, F.W.; writing—review and editing, F.W. and J.L.; supervision, X.-G.M.;
funding acquisition, X.-G.M. All authors have read and agreed to the published version of the manuscript.
Funding: Science & Technology Department of Sichuan Province Science Project (No. 2019YJ0104).
Acknowledgments: We gratefully acknowledge financial support from the Science&Technology Department of
Sichuan Province Science Project (No. 2019YJ0104).
Conflicts of Interest: The authors declare no conflict of interest.