Current　methods　that　utilize　Fenton-like　reagents　to　remove　persistent　organic　pollutants　suffer　from　several　limitations,　i.e.,　the　reagents　may　release　metal　ions　into　the　sludge　and　cause　secondary　pollution,　the　reagents　are　easily　inactivated　after　use,　and　the　use　of　additives　(e.g.,　2KHSO(5)center　dot　KHSO4　center　dot　K2SO4,　Na2S2O8　and　H2O2)　can　be　costly　but　cannot　be　avoided.　In　this　work,　through　a　one-pot　reaction,　we　prepared　surfactant-free　porous　nano-Mn3O4　as　an　efficient　Fenton-like　reagent.　Without　the　addition　of　external　H2O2,　it　could　remove　86.8%　and　96.9%　of　the　phenol　from　an　aqueous　solution　within　1　and　5　min,　respectively,　and　thus　outperformed　many　other　reported　reagents.　The　underlying　mechanism　for　the　removal　of　organic　pollutants　by　this　Mn3O4　reagent　was　examined.　It　was　found　that　the　low-valence　Mn　in　Mn3O4　reacted　with　the　dissolved　O-2　to　generate　H2O2,　and　the　H2O2　in　turn　created　hydroxyl　radicals　(HO　center　dot)　to　degrade　organic　pollutants.　The　Mn3O4　was　also　annealed　to　generate　porous　nano-Mn2O3,　and　a　comparison　of　the　performance　of　Mn3O4　and　Mn2O3　in　removing　organic　pollutants　revealed　that　low-valence　Mn　in　the　oxides　played　a　critical　role　in　scavenging　the　pollutants.　Note　that　this　novel　nano-Mn3O4　could　remove　pollutants　without　the　addition　of　external　H2O2,　and　it　could　be　easily　reactivated　after　use　through　reduction　by　NaBH4　and　thus　be　recycled.　The　Mn3O4　can　also　be　successfully　applied　to　complex　polluted　water　containing　a　mixture　of　phenolics.　These　findings　pave　the　way　for　developing　other　efficient　and　environmentally　friendly　Fenton-like　reagents　for　removing　organic　pollutants　in　wastewater.