Fig. 3

Opto-electronic response of PBHP-TAPT COF. a Protonation and deprotonation of the triazine moieties with chemical triggers (HCl and NH3 vapours): Pristine, bulk PBHP-TAPT COF orange powder (left) and the activated, red powder, after 2–3 s of exposure to HCl (right). b Solid-state UV/Vis spectra of pristine PBHP-TAPT COF (red), after activation with HCl vapours (blue; dashed and dotted line), and regeneration with NH3 vapours (black; dashed line). c Electrical conductivity of pristine PBHP-TAPT COF (red), after activation with HCl vapours (blue), and regeneration with NH3 vapours (black)