Removing Perfluoro Pollutants PFOA and PFOS by Two-Pronged Design of a Ni₈-Pyrazolate Porous Framework

Inspired by the practical need to remove persistent perfluoropollutantsfrom the environment, we leverage cutting-edge crystal engineeringapproaches. For this, we set our eyes on a recent porous coordinationframework system based on the Ni-8-oxo cluster and pyrazolatelinkers as it is known for its stability to bases and other harshenvironmental conditions. Our designer linker molecule here features(1) pyrazole donors masked by t-butyloxycarbonyland (2) ethynyl side units protected by triisopropylsilyl groups.The former solvothermally demasks to assemble the Ni-8-pyrazolateframework, in which the triisopropylsilyl groups can be post-syntheticallycleaved by guest fluoride ions to unveil the terminal alkyne group(-CCH). The ethynyl groups of the framework solid offer versatilereactions for functionalization, as with perfluorophenyl azide (viaa click reaction) to afford the two prongs of the 1,2,3-triazole baseunit and the perfluoro unit. Together, these two functions make foran effective adsorbent for the topical acid pollutants of perfluorooctanoicacid and perfluorooctanesulfonic acid, with a high apparent rate constant(k (obs)) of 0.99 g mg(-1) h(-1) and large maximum uptake capacity (q (max)) of 268.5 mg g(-1) for perfluorooctanoicacid and k (obs) of 0.77 g mg(-1) h(-1) and q (max) of 142.1mg g(-1) for perfluorooctanesulfonic acid.