Precious metals (Pt and Pd) and rare earth elements (Ce in the form of CeO2) are typical materials for heterogeneous exhaust-gas catalysts in automotive systems. However, their limited resources and high market-driven prices are principal issues in realizing the path toward a more sustainable society. In this regard, herein, a nanoporous NiCuMnO catalyst, which is both abundant and durable, is synthesized by one-step free dealloying. The catalyst thus developed exhibits catalytic activity and durability for NO reduction and CO oxidation. Microstructure characterization indicates a distinct structural feature: catalytically active Cu/CuO regions are tangled with a stable nanoporous NiMnO network after activation. The results obtained by in situ transmission electron microscopy during NO reduction clearly capture the unique reaction-induced self-transformation of the nanostructure. This fi nding can possibly pave the way for the design of new catalysts for the conversion of exhaust gas based on the element strategy.