Hybrid Catalysis Enabling Room-Temperature Hydrogen Gas Release from N‑Heterocycles and Tetrahydronaphthalenes

Hybrid catalyst systems to achieve acceptorless dehydrogenation of N-heterocycles and tetra­hydro­naph­thalenesmodel substrates for liquid organic hydrogen carrierswere developed. A binary hybrid catalysis comprising an acridinium photoredox catalyst and a Pd metal catalyst was effective for the dehydrogenation of N-heterocycles, whereas a ternary hybrid catalysis comprising an acridinium photoredox catalyst, a Pd metal catalyst, and a thiophosphoric imide organocatalyst achieved dehydrogenation of tetrahydro­naphthalenes. These hybrid catalyst systems allowed for 2 molar equiv of H2 gas release from six-membered N-heterocycles and tetrahydro­naphthalenes under mild conditions, i.e., visible light irradiation at rt. The combined use of two or three different catalyst types was essential for the catalytic activity.