Regioselective hydroformylation of sterically hindered olefins over single-atom Rh sites on porous organic polymer incorporating hybrid phosphine ligands

Abstract

Developing heterogeneous catalysts capable of efficient and regioselective hydroformylation of sterically hindered alkenes remains a significant challenge. In this work, we develop a stable and active Rh single-atom catalyst (Rh@POP-X) anchored on a hybrid phosphine-functionalized porous organic polymer (POP) with tailored porosity and high specific surface area, allowing for hydroformylation of sterically hindered diisobutylene (DIB). Comprehensive characterizations including solid-state NMR, AC HAADF-STEM, XPS, in-situ CO-DRIFTS, XAS confirm the atomic dispersion of Rh sites coordinated by phosphine ligands within the crosslinked polymeric network. The optimal catalyst Rh@POP-2 exhibits exceptional performance, achieving >98 % conversion with excellent regioselectivity toward linear isononanal. Remarkably, the Rh@POP-2 catalyst demonstrates high stability, maintaining its catalytic performance over 10 times successive reaction cycles without significant deactivation. The versatility of this catalytic system is further demonstrated by its broad substrate adaptability, enabling efficient hydroformylation of various olefins, including linear, terminal, aromatic, and sterically hindered olefins, to yield their corresponding C₁₊ aldehydes. This work provides a general strategy for designing robust single-atom catalysts for challenging hydroformylation of sterically hindered olefins.