Regioselective hydroformylation of propene catalysed by rhodium-zeolite

Hydroformylation is an industrial process for the production of aldehydes from alkenes 1 , 2 . Regioselective hydroformylation of propene to high-value n -butanal is particularly important, owing to a wide range of bulk applications of n -butanal in the manufacture of various necessities in human daily life 3 . Supported rhodium (Rh) hydroformylation catalysts, which often excel in catalyst recyclability, ease of separation and adaptability for continuous-flow processes, have been greatly exploited 4 . Nonetheless, they usually consist of rotationally flexible and sterically unconstrained Rh hydride dicarbonyl centres, only affording limited regioselectivity to n -butanal 5 – 8 . Here we show that proper encapsulation of Rh species comprising Rh(I)- gem -dicarbonyl centres within a MEL zeolite framework allows the breaking of the above model. The optimized catalyst exhibits more than 99% regioselectivity to n -butanal and more than 99% selectivity to aldehydes at a product formation turnover frequency (TOF) of 6,500 h −1 , surpassing the performance of all heterogeneous and most homogeneous catalysts developed so far. Our comprehensive studies show that the zeolite framework can act as a scaffold to steer the reaction pathway of the intermediates confined in the space between the zeolite framework and Rh centres towards the exclusive formation of n -butanal. Rhodium catalysts confined in zeolite pores exhibit high regioselectivity in the hydroformylation process of propene to high-value n -butanal, surpassing the performance of all heterogeneous and most homogeneous catalysts developed so far.