Abstract
The post-synthesis modification is a highly efficient method for the modification of Metal-organic framework (MOF) materials, which has been used to synthesize MOF materials purposefully that cannot be prepared by direct synthesis and impregnation method. In this work, amino modified ZIF8 with 5-aminotetrazole was prepared by the post synthesis modification method and was employed to reversibly remove SO2 from flue gas. Based on the characterization and analysis of X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and Brunner Emmet Teller (BET), it was found that the functionalized ZIF8 (Zn(5-ATZ)1.5) was a microporous material with a two-dimensional nano-layered structure. According to the SO2 adsorption experiments, the adsorption capacity of SO2 at the concentration of 1.6% vol can reach to 122 mg/g under the optimal conditions (25 °C, 2865 h−1). Five successive adsorption-desorption experiments exhibited that Zn(5-ATZ)1.5 had excellent regeneration performance. The characterization results of Raman Spectra (Raman) and X-ray photoelectron spectroscopy (XPS) as well as the DFT simulation calculations revealed that SO2 mainly interacted with Zn(5-ATZ)1.5 by hydrogen bonds between O of SO2 and amino H in the Zn(5-ATZ)1.5, and the interaction of SO2 with amino N and 5-aminotetrazole N by forming a non-covalent charge transfer complex. This work suggested that Zn(5-ATZ)1.5 is an excellent potential sorbent for SO2 removal.
Highlights
In recent years, more and more metal–organic frameworks (MOFs) are widely used in the research of gas separation [1–3] and purification [4,5] because of their high metal center density, large specific surface area, porous structure and easy modification [1,6,7]
We found that the amino functionalized ZIF8 with 3-amino1,2,4 triazole could be used to adsorb SO2, and it has been confirmed that the introduction of amino groups could enhance the SO2 adsorption capacity due to the formation of hydrogen bond between SO2 and the amino [36]
The spectrum of N 1s slightly shifts from 397.0 to 396.9 eV after Zn(5-ATZ)1.5 adsorbed with SO2 owing to the averaging of the N and S electron density regions. This may suggest that the amino H of Zn(5-ATZ)1.5 interacted with O of SO2 to form hydrogen bonds [50] or the N of amino and the N on the 5-aminotetrazole ring of Zn(5-ATZ)1.5 interacted with S of SO2 to form non-covalent charge transfer complexes [51]
Summary
More and more metal–organic frameworks (MOFs) are widely used in the research of gas separation [1–3] and purification [4,5] because of their high metal center density, large specific surface area, porous structure and easy modification [1,6,7]. The modified ZIFs by PSM are usually more stable than that by physical impregnation, because the ligands interact with the center metals via chemical bonds after the metathesis of organic linkers [17,21,22]. ZIF-71 and ZIF-69 were found to be ideal adsorbents to remove SO2 [32] Ma and his colleague reported the Ethylene diamine tetraacetic acid (EDTA) modified MOF-808 (EDTA-MOF808) exhibited high SO2 adsorption capacity at 273 K and 0.2 bar. We found that the amino functionalized ZIF8 with 3-amino triazole could be used to adsorb SO2, and it has been confirmed that the introduction of amino groups could enhance the SO2 adsorption capacity due to the formation of hydrogen bond between SO2 and the amino [36]. The results of this work hope to provide a theoretical basis for the potential application of Zn(5-ATZ)1.5
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