Spirobifluorene-based electropolymerized films for highly sensitive and reversible detection of TNP in water

•The tetra- and octacarbazolyl-substituted spirobifluorene star-shaped precursors (TCTSp and OCTSp) were designed.•MPNs films (TCTSp-EP and OCTSp-EP) were constructed by EP method.•The higher number of electroactive carbazolyl substituents in the EP precursors improved the electrical activity and sensing properties.•Synergistic mechanism of F o¨ rster resonance energy transfer (FRET) and photo-induced electron transfer (PET) as core TNP mechanisms.•A helpful guideline for developing satisfactory MPNs sensing films based on EP method.