Mesoporous coordinated polymers with single-metal-site iridium for efficient catalysis in propylene hydroformylation

Heterogeneous single-metal-site catalysts (SMSCs) have received increasing attention due to their outstanding stability and recyclability. In this work, a novel Ir-based SMSC was successfully constructed through the coordination polymerization between zirconium and triphenylphosphine derivatives with carboxyl functional groups for efficient propylene hydroformylation with CO. The Ir-based SMSC reported here can achieve a turnover number of over 20,000 (being 7.3 times higher than the most effective Ir-base catalyst to date) with 99% selectivity and 56% yield for aldehyde. Besides, it represents the first example with a higher selectivity of isobutyraldehyde than n-butyraldehyde (i.e., n/i = 0.62) among the reported Ir-based catalysts. The Ir-based SMSC can be easily reused for at least 10 cycles without losing its reactivity, whereas the homogeneous monomer catalyst quickly loses its reactivity after the second cycle. Furthermore, the catalytic mechanism of Ir-based SMSC is proposed based on reaction explorations and in situ co-adsorption tests by the method of diffuse reflectance infrared Fourier transform spectroscopy, which has also been revealed by theoretical calculations. This work provides a novel insight into the design of SMSCs with great potential for application in the hydroformylation field.