Octahedral　CdS-ZnS　composites　were　synthesized　using　a　simple　method　of　cation　exchange　and　hydrothermal　treatment,　using　Cd3(C3N3S3)2　(denoted　as　Cd3(TMT)2)　as　a　precursor　and　Zn2+　for　ion　exchange.　In　the　spontaneous　ion　exchange　process,　there　is　the　formation　of　compact　heterojunctions　and　three-dimensional　octahedral　structures.　By　controlling　the　ion　exchange　level,　the　composition　of　(CdxZn1-x)3(TMT)2　hybrid　nanomaterials　can　be　regulated,　and　the　composite　can　be　used　as　a　template　to　generate　octahedral　CdS-ZnS.　Photocatalytic　oxidation　of　toluene　to　benzaldehyde　was　used　as　a　model　reaction　to　evaluate　the　performance　of　the　as-prepared　samples,　and　the　CZ-2　catalyst　shows　the　highest　photocatalytic　activity,　giving　a　benzaldehyde　formation　rate　of　1078　μmol·g-1·h-1　without　the　need　of　any　solvent.　The　excellent　performance　is　ascribed　to　the　octahedral　structure　which　is　large　in　specific　surface　area　and　compact　in　heterojunctions.　It　is　envisaged　that　the　method　is　suitable　for　the　generation　of　heterojunctions　for　photocatalytic　purposes.　Copyright　©　2020　American　Chemical　Society.