The 4-amino-1,8-naphthalimide Tröger's base functionalized triazine covalent organic polymer TB-TZ-COP was synthesised and employed as a "turn-on" fluorescent and a colorimetric sensor for the discriminative sensing of volatile organic compounds; the TB-TZ-COP displaying the largest fluorescent enhancement and high sensitivity for 1,4-dioxane, a harmful environmental pollutant classified as a Group 2B carcinogen. © 2019 The Royal Society of Chemistry.