Nanoarchitectonics of bipyrazole-based porous organic polymer for iodine absorption and fluorescence sensing picric acid and formation of liquid complex of its (poly)iodide ions

A new bipyrazole-based porous organic polymer, TMBPH, was constructed by a nucleophilic substitution polymerization reaction with π-electron-rich 3,3′,5,5′-tetramethyl-4,4′-bipyrazol (TMBP) and hexachlorocyclotriphosphazene (HCCP). Its Brunauer-Emmett-Teller (BET) and Langmuir surface area are 68.97 and 160.69 ​m2 ​g-1, respectively, and its pore volume is 0.0851 ​cm3 ​g-1. TMBPH has a good thermal stability and displays excellent guest uptake of 5.86 ​g ​g-1 in iodine vapor. Interestingly, TMBPH presents a liquid polyiodide complex because of its high iodine adsorption capacity and low pore volume. TMBPH can also adsorb iodine in the solution, and the absorbed iodine can be released at higher temperatures or in the solution. TMBPH as an adsorbent is recovered and reused easily. Furthermore, fluorescent study indicated that TMBPH exhibits high sensitivity to electron-deficient picric acid (PA) via fluorescence quenching. Thus TMBPH can become an ideal absorbent for I2 and fluorescent sensing material for PA to address environmental issues.