Reduction Polymerization of CO₂ with Phenylene Silanes Catalyzed by Single Component B(C₆F₅)₃

CO₂ is an abundant C1 resource but a green-house gas and chemically inert. Thus, its utilization has been a promising but challenging project. Herein, we report the unprecedented polymerization of CO₂ and C₆H₄(SiMe₂H)₂ using B(C₆F₅)₃ alone under mild conditions to give poly(silphenylene siloxane) accompanied by releasing CH₄. The copolymerization can be extended to comonomers of phenylene silanes bearing functional groups. Moreover, it combines with Piers-Rubinsztajn reaction to establish a tandem polymerization system to achieve super thermal resistant poly(siloxane-co-silphenylene siloxane)s. Density functional theory reveals that B(C₆F₅)₃ is activated by silanes to form free HB(C₆F₅)₂, which is the true active species for CO₂ reducing to borylformate, the rate controlling step of the polymerization procedure. The subsequent multiple reductions of borylformate to CH₄ and the step-growth to poly(silphenylene siloxane)s can be fulfilled by both B(C₆F₅)₃ and HB(C₆F₅)₂, and the former shows a slightly higher activity. This work opens a new avenue of utilizing CO₂ to fabricate polysiloxanes that is unable to access using current manners.