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

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) 2 P 2 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/ m PPh 3 &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).