Core-shell Co-MOF-74@Mn-MOF-74 catalysts with Controllable shell thickness and their enhanced catalytic activity for toluene oxidation

A series of core-shell Co-MOF-74@Mn-MOF-74 samples with different shell thicknesses were prepared by the seed growth method, which were characterized by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), inductively coupled plasma mass spectrometry (ICP-MS), X-ray photoelectron spectroscopy, nitrogen adsorption-desorption and scanning electron microscopy (SEM). The shell thickness of these MOF samples were successfully controlled by adjusting the mass ratio between MnCl2 center dot 4H(2)O and Co-MOF-74. On this basis, these MOFs were applied to the catalytic oxidation of toluene. The results showed that with the growth of Mn-MOF-74 in the outer layer of Co-MOF-74, the oxidative selectivity of the substrate to benzaldehyde was greatly improved for the synergy between the core layer and shell layer. The conversion of toluene was 22.4%, and the selectivity of benzaldehyde was 98.1%. In addition, the catalyst can transform various substituted toluene into the corresponding aldehydes in highly selectivity and still keep good stability after four catalytic cycles. The selectivity of the corresponding aldehyde is generally above 80%.

Automated summary

By adjusting the mass ratio between different metal-organic frameworks, the thickness of the shell of the MOF samples was successfully controlled, improving the oxidative selectivity of the substrate. In oxidation reactions, the synergistic effect of core-shell structured MOFs increased the conversion rate of the substrate to 22.4% and achieved a selectivity of 98.1%.