A General and Sustainable Strategy for the Depolymerization of Carbamates, Ureas, and Polyurethanes to Specialty Chemicals Enabled by Nickel

Plastics have numerous applications in industrial and household purposes. Thus, their annual production is increasing, thereby generating enormous end-of-life waste. Very often, these polymeric wastes are typically buried underground or discharged into the ocean and is alarming. Notably, recycling rates of such polymers are extremely low; therefore, sustainable solutions for recycling of polymers attracted significant attention. Herein, we have demonstrated a general and sustainable transfer hydrogenation strategy for the depolymerization of carbamates and ureas, including polyurethanes (PU)-the polymeric analogs of carbamates-and lab-made polyurethanes enabled by nickel. A variety of end-of-life PU wastes generated from bike seats and kitchen sponges have been depolymerized into speciality chemicals, such as aromatic diamine and polyols. Catalytic protocols exhibited a broad scope (>52 entries, up to 99% yield) and remarkable functional group tolerance. Mechanistic studies and control experiments were performed to understand the catalytic pathways.