Three-dimensional　(3D)　nanoporous　metals　are　being　increasingly　utilized　in　various　fields　such　as　catalysis,　energy　storage,　and　sensing.　However,　the　conventional　fabrication　approaches　for　3D　nanoporous　metals,　such　as　dealloying　and　template　methods,　require　additional　sacrificial　materials　and　multiple　fabrication　steps　and　generate　chemical　waste.　Herein,　we　propose　a　novel　gaseous　(O2　and　H2)　oxidation-reduction　(GOR)　method　to　directly　transform　various　transition　metals/alloys　into　3D　micron/nanoporous　materials　by　utilizing　the　spontaneous　reconstruction　of　metallic　atoms.　This　method　eliminates　the　need　for　sacrificial　materials　and　acidic/alkaline　solutions,　making　it　facile,　cost-effective,　and　environmentally　friendly.　The　resulting　micron/nanoporous　Ni/Ni　alloy　exhibits　excellent　mechanical　properties,　atomic　hydrogen　adsorption　capability,　and　hydrophilicity,　leading　to　outstanding　electrocatalytic　activity　and　durability　for　hydrogen　evolution　reaction.　©　2024　Elsevier　B.V.