One-Pot Preparation of Nitro-Functionalized Bimetallic UiO-66(Zr-Hf) with Hierarchical Porosity for Oxidative Desulfurization Performance
Guangming Shi, Yalong Liang, Long Nie, Ruodi Huang, Zhaohan Yang, Xinying Liu, Jun Zhou, Qiuli Zhang, Gan Ye
Abstract
Preparation of multifunctional metal–organic frameworks (MOFs) offers new opportunities to obtain ultrahigh synergistic catalytic performance for heterogeneous reactions; however, the application of a one-pot method for preparing multifunctional MOFs remains challenging. Herein, we develop a one-pot green route for synthesizing bimetallic nitro-functionalized UiO-66(Zr-Hf)-NO 2 with hierarchical porosity under solvent-free conditions. The optimal UiO-66(Zr-Hf 0.6 )-NO 2 shows an ultrahigh enhancement of oxidative desulfurization (ODS) efficiency to oxidize sulfur compounds (1000 ppm sulfur) in a model fuel at 40 °C within 12 min due to the introduction of more active Hf sites in the nodes, the increased Lewis acidity of Zr/Hf–O nodes by the electron-withdrawing NO 2 group, and the enhanced diffusion rates by the mesopores. The turnover frequency (TOF) over UiO-66(Zr-Hf 0.6 )-NO 2 at 40 or 50 °C reaches 145.3 or 217.0 h –1 that surpasses the TOF of most reported MOF-based catalysts in the ODS reaction. Quenching and electron paramagnetic resonance experiments confirm that the formed Hf–OH on the Zr/Hf–O nodes can easily decompose the oxidant (H 2 O 2 ) for generating a Hf-OOH-active intermediate and dominate the ODS efficiency. This contribution provides a one-pot solvent-free avenue to synthesize multifunctional MOFs for enhancing their catalytic activities for targeted applications.