Support-free 3D hierarchical nanoporous Cu@Cu2O for fast tandem ammonia borane dehydrogenation and nitroarenes hydrogenation under mild conditions

A support-free hierarchical nanoporous (NP) Cu@Cu2O composite is easily fabricated by dealloying Cu5Al95 alloy in dilute NaOH solution. This bulk material has a support-free spongy structure composed of three-dimensional interconnected ligaments and open pore channels with multimodal pore size distributions. The NP-Cu@Cu2O catalyst exhibits high activity, good chemoselectivity, and excellent recyclability toward one-pot transfer hydrogenation reactions of diverse nitroarenes to anilines. NP-Cu@Cu2O can effectively activate ammonia borane under mild conditions and complete the transfer hydrogenation reactions with high yields within a short time period of 5 min Cu2O formed at the nanoporous surface is proposed to be the actual active site causing this advanced performance. The main reaction intermediates were successfully separated and characterized, and a plausible condensation mechanism has been proposed for nitro reduction. •NP Cu@Cu2O was easily made by dealloying the CuAl precursor alloy in NaOH solution.•NP Cu@Cu2O has unsupported spongy structure with multimodal pore size distribution.•NP Cu@Cu2O shows high chemoselectivity for the reduction of various nitro compounds.•NP Cu@Cu2O shows high structure stability and reproducibility upon recycling 5 times.