Encapsulation of Phosphotungstic Acid into Metal–Organic Frameworks with Tunable Window Sizes: Screening of PTA@MOF Catalysts for Efficient Oxidative Desulfurization

Abstract

Clean fuels with extremely low sulfur content are highly desirable due to environmental concerns. Herein, three water-stable and ecofriendly metal−organic frameworks with tunable window diameters, denoted as MOF-808X, have been employed as PTA solid supports. An array of PTA@ MOF-808X composites were facilely synthesized via the encapsulation strategy. With tunable window sizes and adjustable PTA loading amounts, the obtained PTA@MOF-808X composites were screened for catalytic oxidative desulfurization (ODS) with H 2 O 2 serving as oxidant. The experiments found that 42% PTA@MOF-808A had the highest catalytic ODS activity and could completely remove dibenzothiophene (DBT) in a model fuel with an initial sulfur content of 1000 ppm within 30 min, which falls far below the acceptable limits for fuel standards (10 ppm). Further investigations revealed that this high catalytic activity could be attributed to the cooperative catalysis of metal clusters in the host framework and the guest PTA molecules. Moreover, 42%PTA@MOF-808A could be facilely recovered and reused for at least five runs without loss of catalytic activity. Having a combination of eco-sustainability, high stability, high catalytic activity, and good recyclability, 42%PTA@MOF-808A therefore represents a new benchmark material for catalytic ODS and provides a new perspective for ultradeep desulfurization.

Metal‐Organic Framework‐Based Catalysts for Oxidative Desulfurization

“…Engineering the window size of a MOF has evolved as a smart solution to effectively immobilize POMs on MOFs. This methodology has been used for the preparation of POM@MOF‐808 using formic, acetic or propionic acid respectively as coordinating monocarboxylate group . The complete DBT conversion was accomplished with H 2 O 2 within only 30 minutes for a PTA supported onto acetic acid modulated MOF‐808.…”

Preparation and characterization of novel polyoxometalate/CoFe2O4/metal–organic framework magnetic core–shell nanocomposites for the rapid removal of organic dyes from water

“…28 POMbased metal-organic frameworks (POM@MOFs) are a class of crystalline porous materials integrating the advantages of polyoxometalates (POMs) and metal-organic frameworks (MOFs), and are widely used as catalysts and adsorbents. [29][30][31] When the POM@MOFs materials are used in the elds of adsorption, adsorbate molecules can diffuse into the cages of MOF, and the POM polyanions previously encapsulated in the cages can act as additional active sites for adsorption. The introduction of POM clusters into MOF cages is an effective strategy for producing materials with enhanced adsorption performances.…”

Restricting Polyoxometalate Movement Within Metal-Organic Frameworks to Assess the Role of Residual Water in Catalytic Thioether Oxidation Using These Dynamic Composites

“…Steric trapping relies on a MOF whose pores can accommodate a POM, but whose apertures are much smaller than the POM thus preventing POM diffusion out of the MOF (Song et al, 2011;Salomon et al, 2015;Cai et al, 2019). This aperture dependence was investigated in a recent report (Lin et al, 2018). Lastly, functionalities in MOFs can impart favorable electrostatic interactions (Férey et al, 2005).…”