Excellent catalytic performance over acid-treated MOF-808(Ce) for oxidative desulfurization of dibenzothiophene

Abstract

Developing highly active oxidative desulfurization (ODS) catalysts has practical value. Recently, Ce-based metal–organic frameworks (MOFs) have been tried as ODS catalysts because they not only possessing Lewis acidity similar to Zr- or Hf-based MOFs, but also exhibiting superior redox activity. However, MOF-808(Ce) synthesized by the conventional method is less catalytic activity due to the lack of defect sites. Therefore, in this contribution, MOF-808-F, after acid treatment, removes the coordination formic acid and forms unsaturated coordination metal sites; the resultant MOF-808-F-H exhibits significantly enhanced catalytic activity. Moreover, the effects of acid concentration and treatment time on the structure and performance of MOF-808-F were investigated, and the catalytic parameters were optimized. MOF-808-F-H could fully catalyze oxidative dibenzothiophene (DBT) within 6 min at 50 °C, achieving a high turnover frequency (180.3 h−1) and excellent catalytic activity (93.9 mmol g-1h−1), which exceeded most reported ODS catalysts including Zr-MOF-808 (70 mmol g-1h−1). And the catalyst could be recycled three times without significant loss of catalytic performance. In the catalytic system, two kinds of reactive oxygen species participate in the oxidation of DBT, and a possible catalytic mechanism of Ce-based MOFs in ODS was proposed accordingly. The excellent catalytic ability of MOF-808-F-H is mainly attributed to the good Lewis acidity, redox activity, and large pore size brought by its open metal sites.