Phosphomolybdic acid encapsulated in ZIF-8-based porous ionic liquids for reactive extraction desulfurization of fuels

Abstract

Porous ionic liquids (PILs), with permanent porosity and fluidity, have been drawing great attention in theoretical research and application. Herein, a novel PIL (HPMo@ZIF-8-PIL) was fabricated by dispersing a phosphomolybdic acid-modified zeolitic imidazolate framework-8 (ZIF-8) into an ionic liquid for deep reactive extraction desulfurization. Size calculation results show that 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonylimide) ([Emim][NTf₂]) with larger ion sizes cannot occupy pores of ZIF-8. In detail, the structure along with permanent porosity was well characterized by gas absorption and molecule displacement experiments, and it was found that HPMo@ZIF-8-PIL can not only promote the dispersion of the catalytically active sites but also retain the good liquidity and excellent extraction ability of ionic liquids. At room temperature, 100% removal of dibenzothiophene sulfur in a model oil could be achieved within 2 h using HPMo@ZIF-8-PIL and hydrogen peroxide as the catalyst and oxidant, respectively. Besides, the successful preservation of porosity increases the probability of contact between the oxidant and active sites, which is also in favor of the promotion of desulfurization performance. This work offers a new method for the modification of porous frameworks to construct PIL catalysts, which will provide a new insight into the application of PILs.