MOFs meet monoliths: Hierarchical structuring metal organic framework catalysts

Structuring heterogeneous catalysts from the micro- to the macro-level is essential for efficient catalyst utilization. The optimized synthesis and the catalytic performance of a Metal-Organic Framework, MIL-101(Cr), immobilized on a monolithic structure is presented. Secondary seeded growth is the optimal procedure to obtain uniform coatings of ∼9 wt.% inside the monolith channels. A monolithic stirrer reactor has been used as playground for exploring reactivation procedures of MIL-101 for the selective oxidation of tetralin in the liquid phase. The presented results confirm the long-term stability of the catalyst, and the absence of any transport limitations in this reaction. The easy recovery of the catalyst allows performing as many reuses as necessary, something impossible to realize when working in the often-practised slurry operation mode. The reported results demonstrate that MIL-101(Cr) undergoes reversible deactivation attributed to the strong adsorption of products on the Cr sites. Applying the proper regeneration procedure (washing in chlorobenzene and air treatment @ 523 K) the initial performance is fully recovered.