Photocatalytic　conversion　of　CO2　into　value-added　products　is　considered　a　sustainable　strategy　to　mitigate　CO2　over-emission.　However,　achieving　favorable　performance　generally　relies　on　valuable　additives　such　as　sacrificial　organic　electron　donors,　which,　in　turn,　limit　its　applicability.　In　this　study,　we　tested　dissolved　effluent　organic　matter　(dEfOM)　derived　from　domestic　wastewater　as　an　alternative　hole　scavenger　during　CO2　photoreduction　over　a　ternary　photocatalyst　(CTF-1-Bi-BiOBr)　composed　of　CTF-1,　Bi,　and　BiOBr.　Impressively,　the　optimal　CTF-1-Bi-BiOBr　catalyst　demonstrated　remarkable　dEfOM　degradation　and　CO　production　(2.933　μmol　g−1　h−1)　in　a　cascading　oxic-anoxic　photocatalytic　process.　This　enhanced　activity　was　attributed　to　the　establishment　of　an　S-scheme　structure　between　CTF-1　and　BiOBr,　with　Bi-metal　serving　as　the　carrier　recombination　centre,　allowing　holes　and　electrons　with　greater　redox　capacity　to　be　retained.　Importantly,　we　discovered　that　smaller　intermediates　formed　during　the　oxic　stage　can　serve　as　extraordinary　electron　donors　in　the　succeeding　anoxic　stage.　Spectroscopic　and　electrochemical　characterization　techniques　revealed　that　pre-oxidized　dEfOM　was　more　effective　in　preventing　the　recombination　of　photoinduced　carriers　compared　to　untreated　dEfOM,　highlighting　its　improved　electron　donating　propensity.　This　study　provides　innovative　insights　for　simultaneously　achieving　wastewater　purification　and　carbon　emission　reduction　through　a　more　economical　pathway.　©　2023　The　Royal　Society　of　Chemistry.