Sn-Based Inorganic Deep Eutectic Solvents for Efficient Oxidative Desulfurization with Superior Recyclability

Deep eutectic solvents (DESs) have garnered significant attention as green solvents, particularly for their potential in the oxidative desulfurization (ODS) of fuel oils. However, conventional organic DESs often face challenges related to poor stability during recycling, which has impeded their practical application. To overcome this limitation, this study introduces a novel inorganic Sn-based DES, ingeniously designed through coordination and hydrogen bonding interactions. Experimental results demonstrate that the tin tetrachloride/phosphoric acid (SnCl4/PA) system achieves a remarkable sulfur removal efficiency, reaching 100% under optimized conditions. Notably, it exhibits exceptional cycling stability, maintaining high performance over nine consecutive reuse cycles. This performance significantly outperforms previously reported organic DESs. A mechanism study, combining experimental characterization with density functional theory (DFT) calculations, reveals that the coordination interactions between SnCl4 and PA synergistically enhance both catalytic activity and cycling stability. Thus, this study provides a novel and effective approach for the development of efficient ODS processes using inorganic DESs.