Light- and Heat-Responsive Frustrated Lewis Pair Enables On-Demand Fixation of Ethylene

Frustrated Lewis pairs (FLPs) have been widely utilized as useful reagents and catalysts for activation of small molecules (SMs) through thermally controlled equilibrium formation of FLP-SM adducts. Herein, we report a light- and heat-responsive FLP system for on-demand fixation of ethylene. The system realizes capture and release of ethylene orthogonally triggered by visible light and heat, demonstrating potential utility as a nonmetallic and environmentally benign method for separation and storage of ethylene. The applicability to other alkenes is also demonstrated. Mechanistic investigations clarify that the photoexcited FLP enables stepwise radical addition to ethylene, followed by skeletal rearrangement to afford the FLP-ethylene adduct, which undergoes thermally promoted, concerted retro-cycloaddition to release ethylene and the free FLP. As a synthetic application, nonequilibrium, selective cis-to-trans isomerization of cyclooctene is achieved through the capture and release of cyclooctene with the FLP. This work discloses unique photochemical reactivity and application of FLPs, leading to further expansion of FLP chemistry into chemical science.