Reduction of CO₂ to methanol using aluminum ester FLPs

Herein we report the synthesis of Al-based esters containing halogenated benzene rings. These Lewis acids were paired with phosphines to form frustrated Lewis pairs (FLPs) which could subsequently bind CO₂. While these FLPs were not sufficiently water-stable to catalyze the reduction of CO₂ to MeOH using NH₃BH₃ as the reductant, we examine the effect of varying Lewis acid strength. Frustrated Lewis pairs (FLPs) are combinations of Lewis acids and Lewis bases where the acid and base are either sterically or geometrically restricted from interacting as strongly as their electronic structures would allow. This effect leads to enhanced reactivity towards small molecules and, consequently, interest in their potential as metal-free catalysts [1-5]. To-date, the biggest success has been based around the ability of a myriad of systems to heterolytically cleave H₂ and perform catalytic hydrogenations [2,3].