Stacking MFI zeolite structures for improved Sonogashira coupling reactions

We designed a zeolite stacking structure by using hydraulic pressing and programmed temperature calcination synthesis procedures. ZSM-5 type zeolites with particle sizes of approximately 100 nm, 1 μm and 2 μm were used to synthesize stacking ZSM-5 with a size ranging from 45 to 63 μm. The prepared ZSM-5 zeolite stacking structure was used as a support to deposit palladium. The performance of the palladium/stacking ZSM-5 was investigated on Sonogashira coupling reactions. Stacking samples with micro-sized units (1 μm and 2 μm) showed a 200–300% higher turnover number (TON) than their unit counterparts. However, stacking samples with nano-sized units (100 nm) showed decreased TON conversion compared with that of their unit counterparts, probably due to partial destruction of the nano-sized ZSM-5 structure during the stacking synthesis process at high temperature. The palladium/stacking ZSM-5 (micro-sized units) also showed better conversion on different bromides and alkynes than that of traditional homogenous catalysts. Moreover, the stacking composites showed good durability by recycling 4 runs without losing significant catalytic activity. The design of the stacking MFI structure exhibited improved catalytic activity, sustainability and hierarchical-resemblance properties.