Yibo Zhang,Wei Wang,Chunlai Liu,Peihang Shen,Zelong Liu,Jianglei Hu,Fengwei Shi
In this work, we successfully synthesized a novel composite (HPW@MOF-199/SBA-15C, PMS-15C) in which MOF-199 encapsulated HPW catalyst (named HPW@MOF-199) was confined in SBA-15C, which is the carboxy-functionalized SBA-15. Physicochemical properties of the composites PMS-15C were systemically characterized by N 2 adsorption–desorption isotherms, wide-angle and low-angle XRD, XPS, FT-IR, SEM, and TEM. The results exhibited that HPW@MOF-199 had been successfully synthesized and embedded into the SBA-15C pores by COOH on the surface of SBA-15C. Meanwhile, the composites PMS-15C exhibited high activity and excellent reuse properties in the esterification reaction of acetic acid and ethanol, and no evidence of aggregation, leaching, or inactivation of HPW@MOF-199 during repeated use. The good dispersion of HPW within the MOF-199 cage and the interaction between HPW@MOF-199 and SBA-15C may be responsible for the good catalytic activity as well as the high stability of PMS-15C.
Yibo Zhang,Yang Liu,Wei Wang,Chunlai Liu,Hongyu Zhou,Na Wang,Jianglei Hu,Fengwei Shi
Metal-organic framework (MOF)-based composites have received significant attention for catalytic applications and are believed excellent heterogeneous catalysts. In this article, we prepared a new type of material, HPW@MOF-199/SBA-15C (PMS-15C). For this material, the MOF-199 encapsulating Keggin-type phosphotungstic acid (HPW) was grown inside the pores of the SBA-15 functionalized by carboxylic acids. The N 2 adsorption-desorption isotherms and pore size distributions, X-ray powder diffraction, transmission electron microscopy, and scanning electron microscopy analyses showed that the PMS-15C composites had an ordered two-dimensional hexagonal mesoporous structure, in which HPW encapsulating by MOF-199 loaded into the SBA-15C. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy indicated that HPW was successfully loaded, and the Keggin structure of HPW in PMS-15C remained unchanged. With the reaction of acetic acid and ethanol, the catalytic performance of PMS-15C was studied. Under the optimal conditions, ethyl acetate yield reached 81.4 %. The forward reaction rate was 0.432 mL mol −1 min −1 , and the activation energy was 38.35 kJ mol −1 . And the data were found to be consistent with the second-order reversible reaction kinetic model. The catalytic activity of the PMS-15C-0.2 composites remained stable after five catalytic cycles. In addition, the esterification of n-octanol/acetic acid and ethanol/oleic acid were studied using PMS-15C-0.2 as the catalyst. The results suggested that the catalytic activity of PMS-15C-0.2 was weakened upon increasing the substrates’ alkyl chain length.
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