Highly efficient adsorption of benzothiophene from model fuel on a metal-organic framework modified with dodeca-tungstophosphoric acid

Abstract

Reduction of sulfur-containing compounds from fossil fuel is vital. This work reports on the adsorptive removal of benzothiophene (BT) from liquid fuel using a highly porous metal-organic framework based on a bicomponent zirconium(IV) benzene-tricarboxylate Zr(BTC), and its post-synthetically modified hybrid form with dodeca-tungstophosphoric acid (HPW/Zr(BTC). The HPW loading for the high-performing hybrid adsorbents was 0.5–2.0 wt/wt of W/Zr. Temperature and concentration dependent BT adsorption data were in good agreement with the non-linear Langmuir model combined with a van’t Hoff description of the heat of adsorption. The maximum predicted adsorption capacities were estimated to be 290 and 238 mg.g−1 for HPW(1.5)/Zr(BTC) and Zr(BTC) comparable to the contemporary reported adsorbents. The adsorption kinetics followed a pseudo-second order model, which was related to the low concentration of BT used for these studies. Although the highly porous Zr(BTC) had good adsorptive sites, its adsorption capacity was enhanced by incorporation of HPW, this was attributed to availability of added acid sites for adherence of basic BT. The adsorption findings were further corroborated with DFT calculations, which showed favorable BT adsorption with calculated binding energies of −140.2 and −47.3 kJ.mol−1 for HPW(1.5)/Zr(BTC) and Zr(BTC), respectively. Much of adsorption sites were retained after regeneration of adsorbents.