Tuning the framework flexibility and equilibrium of HRh(CO)2P2 active isomers in single-atom Rh/P&N-POPs catalysts for hydroformylation reactions

Abstract

Tuning the microenvironment surrounding single atom metals is an effective but challenging way to regulate the performance of single atom catalysts (SACs). Herein, we prepared a series of P, N-abundant porous organic polymers (P&N-POPs) with diverse framework flexibility and coordination ability to serve as SACs’ carriers. The microenvironment (coordination site, coordination number) surrounding Rh and the equilibrium of ea/ee-HRh(CO)2P2 active species were effectively regulated in Rh/P&N-POPs catalysts. Our study shows that the specific active ee-HRh(CO)2(P)2 species confined in the flexible polymeric skeleton endowed the Rh/mPPh3&PPD-POP with superior activity (TOF = 2000 h−1), selectivity of aldehydes (93.5 %), ratio of linear aldehyde to branched aldehyde (l/b ratio = 15.9), favorable stability (10 recycling runs without activity loss) and extensive substrate applicability (19 kinds of olefins) in hydroformylation reactions. Multiple characterization techniques (EXAFS, STEM, in-situ FTIR etc.) were employed to get insights into this effective strategy to regulate the performance of single atom catalysts (SACs).