Conjugated polymers are attractive materials for the detection of chemicals because of their remarkable pi-conjugation and photoluminescence properties. In this article, we report a new strategy for the construction of molecular detection systems with conjugated microporous polymers (CMPs). The condensation of a carbazole derivative, TCB, leads to the synthesis of a conjugated microporous polymer (TCB-CMP) that exhibits blue luminescence and possesses a large surface area. Compared with a linear polymer analogue, TCB-CMP showed enhanced detection sensitivity and allowed for the rapid detection of arenes upon exposure to their vapors. TCB-CMP displayed prominent fluorescence enhancement in the presence of electron-rich arene vapors and drastic fluorescence quenching in the presence of electron-deficient arene vapors, and it could be reused without a loss of sensitivity and responsiveness. These characteristics are attributed to the microporous conjugated network of the material. Specifically, the micropores absorb arene molecules into the confined space of the polymer, the skeleton possesses a large surface area and provides a broad interface for arenes, and the network architecture facilitates exciton migration over the framework. These structural features function cooperatively, enhancing the signaling activity of TCB-CMP in fluorescence-on and fluorescence-off detection.