Tailoring the microenvironment of ruthenium centers by crosslinker geometry in PIL frameworks for efficient hydroformylation

Olefin hydroformylation on polymer-supported catalysts has shown high activity; however, most of the support was fabricated for grafting a molecular catalyst. Herein, the microenvironment of Ru nanoparticles in poly(ionic liquid) (PIL) frameworks was tailored by employing two crosslinkers of cage-like octavinyloctasilasesquioxane (POSS) and planar, star-shaped 4,4″-divinyl-5′-(4-vinylphenyl)-1,1′:3′,1″-terphenyl (TVPB). Compared with TVPB, POSS promotes not only Ru aggregation but also local enrichment of Cl, which leads to larger but electron-deficient Ru domains for Ru@PIL at an identical Ru density. Ru@PIL^P_1/2 shows high activity in 1-hexene hydroformylation, with a turnover number (TON) up to 1,038, which drops rapidly as Ru density increases from 4 to 50 μg/m². By contrast, Ru@PIL^T_1/1 maintains a TON around 700. Additionally, the POSS-based PIL has a high TON across a wide POSS/IL ratio. A high POSS content causes larger Ru domains and weaker CO/H₂ adsorption, yet local Cl enrichment mitigates activity loss. This work offers another design platform for efficient PIL-supported hydroformylation catalysts.