Ligand Modified Metal Organic Framework UiO-66: A Highly Efficient and Stable Catalyst for Oxidative Desulfurization
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Ligand Modified Metal Organic Framework UiO‑66: A Highly Efficient and Stable Catalyst for Oxidative Desulfurization Xiaoyuan Liao1,2 · Xiayang Wang1 · Fan Wang1 · Yue Yao1,2 · Shuxiang Lu1,2 Received: 2 July 2020 / Accepted: 5 November 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract It is reported that the UiO-66(Zr) material could catalyze oxidative desulfurization (ODS) reaction, but its stability is inferior. In this work, a family of functionalized UiO-66(Zr) with different groups (–NH2, –NO2, –Br) were prepared to enhance this material’s activity and stability. Characterizations and ODS tests show that the groups have profound influence over the physicochemical properties of UiO-66(Zr). Among functionalized UiO-66(Zr), UiO-66(Zr)-NO2 exhibited the best ODS activity, their ODS performance is linear correction with their Hammett values. Recycling experiments indicate UiO-66(Zr)NO2 has no deactivation. Keywords UiO-66(Zr) · Oxidative desulfurization · Functionalized · Excellent stability
1 Introduction The combustion of fuel oil will release S OX in the air, which causes hazards to the environment and human health [1]. With the increasingly stringent environmental protection regulations, the research on low sulfur content of fuels ( UiO-66-NH2 > UiO66-NO 2 > UiO-66-Br, respectively. It shows that, after treated by ligands, the BET surface area of UiO-66(Zr) reduced, and confirmed that the ligands has negative influence over its BET results, especial for -Br group. In addition, the pore volume of UiO-66(Zr)-X maintained porosity after ligand modification, which is consistent with the previous works [35]. Besides, The TGA analyses (Figure S1) showed the stability of has the order of UiO-66(Zr) > UiO-66(Zr)Br > UiO-66(Zr)-NO2 > UiO-66(Zr)-NH2. Comparing the weight loss observed between 250 and 550 °C, it appears evident that the stability of UiO-66(Zr) derivatives are remarkably lower than UiO-66(Zr). But the UiO-66(Zr)-NO2 has best ODS activity, this result shows that the ODS has direct relationship with heart stability and BET surface area. X-ray photoelectron spectroscopy (XPS) could investigate the charge states of atoms and probe the electronic effects of ligands. Figure 4a gives an overview of the survey spectrum of UiO-66(Zr)-X samples, which shows the main elements of samples are C, O, N, Br and Zr. The high resolution Zr 3d spectra of UiO-66(Zr)-X samples are shown in Fig. 4b. The peaks of Zr 3d region deconvolute into two peaks, i.e., Zr 3d5/2 and Zr 3d3/2, the peak at 182.8 eV can be assigned to Zr 3 d5/2 of the zirconium atoms in Z r6 clusters, and the peak at 185.1 eV can be ascribed to Zr 3d3/2 of the zirconium atoms in missing-linker defects ( Zr4+, Zr–OH2 and Zr–OH) [26]. The XPS results for UiO-66-NH2 (Zr) show a 0.4 eV increase in Zr 3 d3/2 binding energy as compared to UiO66(Zr), demonstrating the electron-donating effect of the NH2 functional group. Comparison to pristine UiO-66(Zr), UiO-66(Zr)-Br shows 0.1 eV decrease due to the electronattractin
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