The selective deposition of Fe species inside ZSM-5 for the oxidation of cyclohexane to cyclohexanone

The design of efficient iron-based catalysts remains a great challenge for selective cyclohexane oxidation to cyclohexanone under mild conditions. Because of the complex distribution of iron location on the support, the selectivity is always low. Here, we report a general strategy to selectively deposit highly-dispersed FeO_x into the micropore of ZSM-5 by atomic layer deposition (ALD). The framework of ZSM-5 and the Brønsted acid sites are intact during ALD, and the Fe species are selectively deposited onto the defect and Lewis acid sites of ZSM-5. Besides, more Fe-O-Si bonds are formed over FeO_x/ZSM-5 with a low loading of Fe, while FeO_x nanoparticles are generated at high Fe loading. They cannot be realized by the traditional solution method. The obtained FeO_x/ZSM-5 catalysts perform high selectivity of cyclohexanone (92%–97%), and ALD cycle numbers of FeO_x control the activity. Compared with the Fe nanoparticles, the Fe-O-Si species performs higher turnover frequency and stability in the oxidation reaction.[Figure not available: see fulltext.]