One-Pot Preparation of Nitro-Functionalized Bimetallic UiO-66(Zr-Hf) with Hierarchical Porosity for Oxidative...

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)-NO₂ with hierarchical porosity under solvent-free conditions. The optimal UiO-66(Zr-Hf_0.6)-NO₂ 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 NO₂ group, and the enhanced diffusion rates by the mesopores. The turnover frequency (TOF) over UiO-66(Zr-Hf_0.6)-NO₂ 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 (H₂O₂) 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.