Novel phenyl-phosphate-based porous organic polymers for removal of pharmaceutical contaminants in water

A clean water system is a basic necessity for the survival of living organisms, and thus, addressing the removal of emerging contaminants from aquatic systems is a priority research topic to reinstate the ecosystem balance for a sustainable future. In this study, we have synthesized two types of novel phosphate based porous organic polymers (P-POP-1 and P-POP-2) by one-pot straightforward synthesis with a Friedel-Crafts reaction using diphenyl phosphate and 1,1,2,2-tetraphenylethylene as precursors for P-POP-1, and diphenyl phosphate and 1,3,5-triphenylbenzene for P-POP-2. A series of material characterization using powder X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, N-2 adsorption-desorption, and thermal gravimetric analysis showed that P-POP-1 and P-POP-2 have porous structures with intact phosphates and show a specific surface area of 714 and 581 m(2)/g, and mesoporosity of 19.6% and 32.5%, respectively. Using caffeine, diclofenac, and carbamazepine as three target pharmaceutical compounds, P-POP-2 showed excellent maximum adsorption capacity (caffeine 301 mg/g, diclofenac 217 mg/g, and carbamazepine 248 mg/g). P-POP-2 also exhibited an adsorption equilibrium time of 50 min, which is shorter than those of other materials. Furthermore, P-POP-2 exhibited high pharmaceutical compound removal ( > 95% for caffeine and carbamazepine; > 82% for diclofenac) in the presence of other competing cations and humic acid. The repeated use of P-POPs over 5 cycles showed < 10% deterioration in adsorption capacities. Results from this study show that phosphate-based porous organic polymer material could be a promising adsorbent for removing pharmaceutical compounds in water.