Introducing VO2+ Group in Phosphomolybdic Acid and Supporting on MOF-808 for Efficient Oxidative Desulfurization.

Herein, by introducing a VO2+ group into the microstructure of phosphomolybdenic acid (PMA) and loading it onto MOF-808, a series of composite catalysts were obtained by reducing the V element with Vitamin C (ascorbic acid). V atoms exist in the secondary structural units of phosphomolybdic acid as [VO(H2O)5]H[PMo12O40]. Surprisingly, the VC-VO-PMA/MOF-808 completely removed DBT and 4,6-DMDBT from the simulated oil in 12 min. The EPR and XPS results verify the electronic structure and valence state of V4+ in the composites. The oxygen vacancy and V4+ generated by VC modification in VC-VO-PMA/MOF-808 have positive effects on the oxidation desulfurization (ODS) activity. Based on the design of the microstructure and electronic structure, this study provides a new paradigm for the development of readily available and efficient ODS catalysts.

Highly Efficient and Reusable Denitrogenation Adsorbent Obtained by the Fluorination of PMA-MIL-101.

A simple but efficient strategy to improve the ability of adsorptive denitrogenation (ADN) of MIL-101(M101) was studied by the in situ encapsulation of phosphomolybdic acid (PMA) and the subsequent purification of the as-synthesized product by the NH4F solution. After the NH4F treatment, the vast majority of PMA was removed, loss of organic ligand (BDC) was observed, and the fluorination of the hydroxyl group in the M101 structure occurred. The ADN activities of the Cr-MOF matrix composites before and after fluorination were studied in detail. The rest of PMA interacts strongly with M101 and assists the ADN activity. Coordination unsaturated metal sites (CUS) in M101 are formed after fluorination and also contribute to ADN activity. Further, fluoride anions replace most of the hydroxide groups in M101, which can promote the ADN of quinoline (QUI) and indole (IND) through an acid-base interaction and N-atom coordination with the CUS in M101. P-M101-F 5% exhibits the highest adsorptive capacity and excellent regeneration ability. Special emphasis in this work is placed on structure modulation (including PMA doping, CUS creation, and fluorination) of M101 for enhancing ADN activity, which provides a useful scaffold for future research in the rational design of MOF-based ADN catalysts.