Four economic and easily prepared metal-based ionic liquids (MILs) were synthesized based on triethylamine hydrochloride (Et3NHCl) and a series of anhydrous metal chlorides (MClx). The stiochemistry of the as-prepared MILs is characterized systematically. Extraction and catalytic oxidative desulfurization (ECODS) of thiophenic sulfides is then achieved using the as-prepared MILs and molecular oxygen (02) in air as the extractant and oxidant, respectively. The factors that could influence sulfur removal are investigated systematically, and deep desulfurization of oils with different S concentrations and substrates are achieved under optimized conditions simultaneously. Dibenzothiophene (DBT) removal reaches up to 99.4% under the optimized conditions. Sulfur removal with different sulfides decreases in the order of DBT > 4,6-dimethyldibenzothiophene (4,6-DMDBT) > benzothiophene (BT). The influence of the co-existence of alkenes and aromatics is also investigated. Moreover, the used amount of low-cost [Et3NH]FeCl4 is relatively low [V(MIL)/V(oil) = 1:15], and it could be recycled S times without a significant decrease in sulfur removal. Besides, it is verified that sulfur compounds are converted to their corresponding sulfones in the reaction process with the help of gas chromatography mass spectrometry (GC-MS) measurement.