Microporous boron nitride-based porous ionic liquid for enhanced extractive desulfurization of fuel

Fe-based ionic liquids (ILs) exhibit a potential application in extractive desulfurization (EDS) of fuel oil, but struggle from the relatively low sulfur removal in a single extraction. In this work, a new type of porous ionic liquid (m-BN-PIL) was engineered by employing butylpyridinium tetrachloroferrate ([BPy][FeCl4]) as an organic guest and microporous boron nitride (m-BN) as the porous framework. The formation of porous ionic liquid (PIL) promotes electron transport between [BPy][FeCl4] and m-BN, hence enhancing electron densities of pyridinium ring cation ([BPy]+) and boosting m-BN dispersion, which favors the exposure of extraction sites. Furthermore, molecular size simulation and gas absorption experiments have validated the permanent porosity of m-BN-PIL, as has significantly improved mass transfer capacity when compared to pure [BPy][FeCl4]. Both factors induce a significantly promoted EDS performance. Further characterizations verify that the m-BN-PIL remains stable during the extraction process. With m-BN-PIL as an extractant, 59.2 % and 61.8 % desulfurization performances can be achieved over dibenzothiophene (DBT) and 4-methyldibenzothiophene (4-MDBT) under the optimized extraction conditions, respectively. Especially, after four stepwise extraction processes, the extraction efficiency over DBT is high at 98.2 %, achieving deep desulfurization of fuel oil. This study presents a versatile strategy for designing high-performance EDS extractants by constructing strong electronic interactions between ILs and porous frameworks via dispersing m-BN within [BPy][FeCl4].