Designing Cu0−Cu+ dual sites for reversible dehydrogenation and hydrogenation of N-heterocycles

Liquid organic hydrogen carriers (LOHC), which involve reversible catalytic hydrogenation/dehydrogenation cycles, have attracted considerable attention. This study investigates Cu/CuAlO x catalysts with unique Cu 0 –Cu + interfacial sites, which are prepared via structural topological transformation of layered double hydroxide (LDH) precursors. The optimized Cu/CuAlO x catalysts exhibit exceptional catalytic activity in 1,2,3,4-tetrahydroquinoline (THQ) dehydrogenation, achieving a complete conversion of THQ within 1.5 h and a turnover frequency (TOF) value amounts to 19.94 h −1 at 150 °C, which stands at the highest echelon compared with previously reported heterogeneous catalysts. Furthermore, the catalyst also exhibits excellent performance in quinoline hydrogenation (yield >99 %) after 6 h at 60   °C, and the TOF value reaches up to 7.01 h −1 . A comprehensive investigation based on XPS, TEM and XAFS verifies the dual active states Cu 0 and Cu + sites coexisting on nanoparticle surfaces. Both experimental studies ( in situ DRIFTS and XPS) and DFT calculations reveal the pivotal role of the Cu 0  − Cu + synergistic effect in dictating catalytic behavior: the Cu + species preferentially adsorb and activate the N − H bonds and C − H bonds in N-heterocycles; Whereas the Cu 0 site facilitates efficient reassociation of surface adsorbed H atoms and product desorption (H 2 ). This work exhibits substantial potential for implementation in hydrogen storage technologies, offering a viable pathway towards efficient LOHC utilization in clean energy systems.