Photocatalytic Transfer Hydrogenation Using Plastic Hydrolysates as Hydrogen Donor

Abstract

The synthesis of aromatic amines requires harsh conditions or the use of fossil-based hydrogen (H2). Here, we address this shortcoming by demonstrating photocatalytic transfer hydrogenation (PTH) of nitroarenes into anilines employing plastic hydrolysates as electron and proton (hydrogen) donors under ambient temperature and pressure. PTH is achieved using a cobalt-promoted molybdenum sulfide (CoMoS2) electrocatalyst integrated into a carbon nitride (CNx) semiconductor as a photocatalyst in acidic aqueous solution. CoMoS2 reduces nitroarenes to anilines at –0.7 V vs RHE with a Faradaic yield of 70% and superior activity to platinum. The CoMoS2-CNx photocatalyst produces anilines under simulated solar light (AM 1.5G, 25 °C), achieving 83-99% yield from 24 nitroarenes using 4-methylbenzyl alcohol as a model electron donor. Acid hydrolysis of condensation polymers provides a source of alcoholic monomers in aqueous solution that can be used as hydrogen donor for PTH in >80% yields. A technoeconomic analysis (TEA) at pilot scale producing 1 t aniline day⁻1 using polyethylene terephthalate (PET) reveals a cut in cradle-to-gate emissions by ~77% using PTH with CoMoS2-CNx compared to conventional Pd/C hydrogenation with H2 from steam methane reforming (SMR-H2) and a revenue-generating levelized cost of aniline (LCOA) when co-produced with terephthalic, acetic, and formic acids.