The hydroformylation of 1-butene on phosphine modified 1Rh/MOF-5 prepared by different immobilization strategies

Immobilization of the Rh active sites in novel porous materials has attracted attentions for solving the problems of separation and recycling of homogeneous catalysts. In this work, a comparative study of phosphine modified 1Rh/MOF-5 using three different methods was reported, namely 1Rh-P/MOF-5, 1Rh/MOF-5-P and 1Rh/MOF-5-PPh 3 . Similar with the traditional methods, PPh 3 was etched on Rh particles by impregnation in 1Rh-P/MOF-5 and encapsulated in the pores by solvothermal method in 1Rh/MOF-5-P. Moreover, we proposed a novel post-synthesis strategy for grafting phenyl phosphine on the organic linkers in 1Rh/MOF-5-PPh 3. The position of phenyl phosphine in MOFs and the effect of phosphine on the Rh active sites in hydroformylation were investigated by XRD, IR, XPS, TGA and DRIFTS. 1Rh/MOF-5-PPh 3 exhibited the best catalytic activity and stability than 1Rh-P/MOF-5 and 1Rh/MOF-5-P in the hydroformylation of 1-butene. Different P/Rh ratio in P-modified 1Rh/MOF-5 led to the spatial environment change around the Rh active sites. This study showed details in the role of phosphine ligands played in hydroformylation reactions and provided some guidance for MOFs materials in the immobilization of homogeneous catalysts.