Heavy　metals　and　organic　dyes,　such　as　Cr(VI)　and　rhodamine　B　(RhB),　were　usually　both　contained　in　printing　and　dyeing　wastewater.　Despite　extensive　research　on　the　removal　of　RhB　and　Cr(VI)　from　wastewater,　addressing　the　challenge　of　simultaneous　removal　of　mixed　pollutants　remains　a　significant　hurdle.　In　this　paper,　a　Z-scheme　heterojunction,　denoted　as　GQDs/BiOBr/g-C3N4　(GBCN),　was　prepared　from　BiOBr　and　g-C3N4　with　graphene　quantum　dots　(GQDs)　serving　as　electron　transfer　mediators.　This　composite　exhibits　a　nanosheet　morphology　with　an　increased　specific　surface　area　of　7.58　m2/g.　The　synergistic　effects　of　the　coexistence　system　resulted　in　GBCN　achieving　complete　RhB　degradation　within　100　min　and　an　impressive　99.3　%　photoreduction　efficiency　for　Cr(VI).　Density　functional　theory　(DFT)　calculations　and　experimental　results　suggested　that　the　superior　photocatalytic　performance　of　GBCN　was　attributed　to　the　highly　efficient　electron　transfer　and　charge　separation　enabled　by　the　Z-scheme　heterojunction,　in　synergy　with　the　electron　transfer　mediator　and　the　photothermal　effect.　Quenching　experiments　and　electron　spin　resonance　(ESR)　measurements　validated　the　involvement　of　h+,　[rad]O2−,　[rad]OH,　and　1O2　in　the　oxidation　of　RhB,　while　e−　contributed　to　the　reduction　of　Cr(VI).　Fukui　index　calculations　revealed　high　f0　values　for　N2,　N14,　O23,　and　C23　of　RhB　molecules　and　the　degradation　intermediates　of　RhB　were　further　identified　by　LC-MS　analysis.　Finally,　the　reduced　toxicity　of　the　product　after　RhB　degradation　was　affirmed.　This　study　offers　new　insights　into　the　design　of　efficient　Z-scheme　heterojunctions　for　the　simultaneous　removal　of　organic　dyes　and　heavy　metal　ions.　©　2024