Bimetallic Metal–Organic Frameworks MIL-53(xAl–yFe) as Efficient Catalysts for H₂S Selective Oxidation

Abstract

Catalytic oxidation of H2S is a crucial green pathway that can fully convert H2S into value-added elemental S for commercial use. However, achieving high catalytic stability and S selectivity by traditional-metal-based catalysts still remain a major challenge. Herein, a facile one-step solvothermal strategy is designed for the fabrication of bimetallic MIL-53­(xAl–yFe) catalysts. The as-synthesized MIL-53­(1Al–5Fe) possesses ample coordinatively unsaturated metal sites, which served as efficient catalytic sites for the selective oxidation of H2S. As a result, the representative MIL-53­(1Al–5Fe) achieves a S yield of nearly 100% at 100–160 °C with almost no obvious decrease of catalytic stability in the run of 30 h. Under the defined reaction conditions, the bimetallic metal–organic frameworks are obviously superior to MIL-53­(Al) (49.3%) and MIL-53­(Fe) (70.5%) in S yield. This study suggests that the introduction of elemental Al into MIL-53­(xAl–yFe) could effectively modulate the electronic properties and spatial configuration of the catalysts, further conducing the adsorption and activation of H2S and thus accelerating the dissociation of H2S into a key intermediate S* and improving their catalytic performance.

Advances in Resources Recovery of H2S: A Review of Desulfurization Processes and Catalysts

“…In addition to the primary metal oxide-based and carbon-based catalysts, some other materials such as molecular sieves, metal–organic frameworks (MOFs), , graphitic carbon nitride (C 3 N 4 ), and perovskites have also been studied for the catalytic oxidation of H 2 S.…”

“…Furthermore, Al species was incorporated into MIL-53­(Fe) to form bimetallic MIL-53­(xAl-yFe) catalysts. The ample coordinatively unsaturated metal sites are displayed as efficient active sites for the catalytic oxidation of H 2 S. The representative MIL-53­(1Al-5Fe) exhibited a sulfur yield of 100% at 160 °C, which was superior to MIL-53­(Fe) (70.5%) and MIL-53­(Al) (49.3%) …”

MOF-based catalysts: insights into the chemical transformation of greenhouse and toxic gases

“…Furthermore, MIL-53(1Al-5Fe) shows extensive open metal sites necessary for the oxidation reaction. 205 MIL-53(1Al-5Fe) achieves high selectivity (100%) at 100-160 1C, even after 30 h of reaction. By comparing to the pristine materials, MIL-53(Al) and MIL-53(Fe) display 49.3 and 70.5% yield, respectively.…”

Designed Synthesis of Fe/Zr Bimetallic Organic Framework to Enhance the Selective Conversion of H2S to Sulfur

“…Among the myriad family of MOFs, UIO-66­(Zr), which is constructed by Zr­(IV)-carboxylate clusters (Zr 6 (μ 3 -O) 4 (μ 3 -OH) 4 (C 8 H 4 O 4 ) 6 ) and 12 bidentate terephthalic acid (H 2 BDC) to form regular dodecahedral secondary structural units, has unique advantages in the field of catalysis because of its excellent thermal and chemical stability. − Nevertheless, the problem of limited catalytic activity restricts its further development. In order to boost the activity of catalysts, the common strategies are mainly to control the composition, structure, morphology, and particle size of catalysts because these factors have a significant impact on their catalytic properties. − Selective oxidation of H 2 S, as a gas–solid heterogeneous oxidation reaction, mainly occurs in the active center of the catalysts. Therefore, it is highly feasible to enhance the catalytic properties by doping heterometal atoms, which will provide more catalytic active sites and create synergistic effects between different metals. − On this basis, the smaller nanoparticles and larger surface areas not only improve the accessibility of the active sites but also enhance their atomic utilization efficiency. − Based on the above discussion, the incorporation of Fe atoms into the framework of UIO-66­(Zr) is highly attractive for the fabrication of bimetallic MOF catalysts with more accessible and reactive active sites for selective conversion of H 2 S to S.…”