Targeted　construction　of　new　covalent　organic　frameworks　(COFs)　with　specific　purposes　and　rationalities　to　build　colorimetric　assay　platform　for　environmental　pollutant　monitoring　have　attracted　increasing　interest.　However,　it　is　still　challenging　due　to　lack　of　available　coordination　sites　inside　COFs　pores　and　only　a　slight　bonding　ability　for　anchoring　metal.　In　this　work,　a　two-dimensional　(2D)　COFs　(termed　as　Tz-COF)　with　high　crystallinity,　excellent　chemical　stability,　and　abundant　sulfur　coordination　in　its　skeletons　was　synthesized　and　used　for　the　confined　growth　of　Au　NPs.　It　was　found　that　the　Au　NPs　showed　significant　dispersibility　for　the　support　of　Tz-COF.　The　proposed　Tz-COF@Au　NPs　possessed　outstanding　Hg　2　+　-activated　peroxidase-like　activity　benefited　from　physicochemical　properties　of　gold　amalgam　and　synergistic　effect　between　COFs　and　Au　NPs　to　oxidize　chromogenic　substrate.　Based　on　highly　efficient　activity　and　distinctive　color　evolution,　the　strategy　for　detecting　Hg　2　+　was　developed　and　successfully　applied　to　determine　the　content　of　Hg　2　+　in　real　environmental　samples.　This　work　manifests　that　a　potential　strategy　to　establish　a　colorimetric　assay　platform　for　environmental　pollutant　monitoring　based　on　the　targeted　manufacturing　of　novel　COFs　with　specific　functions.　(c)　2024　Published　by　Elsevier　B.V.　on　behalf　of　Chinese　Chemical　Society　and　Institute　of　Materia　Medica,　Chinese　Academy　of　Medical　Sciences.