Adsorption mechanism on metal organic frameworks of Cu-BTC, Fe-BTC and ZIF-8 for CO₂ capture investigated by X-ray absorption fine structure

Abstract

Three different commercial metal organic frameworks (MOFs) of Cu-BTC, Fe-BTC and ZIF-8 have been characterized by multiple techniques including CO 2 adsorption/desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS). Particularly, the MOFs powders were sealed inside quartz sample tubes for each step of CO 2 adsorption/desorption, and were sequentially measured for XAFS to identify the short-range structural evolutions on investigated metals (Cu, Fe, Zn). According to the data analyses on X-ray absorption near edge spectroscope (XANES) and extended X-ray absorption fine structure (EXAFS), we can demonstrate that both electronic and local structures of MOFs were almost unchanged between fresh samples and those under the activated/adsorbed/desorbed conditions. This indicates that the CO 2 adsorption of MOFs is mainly governed by the physical driving force.On the other hand, the chemical transformation, i. e. elimination of water in MOFs structure by the activation (13.3 kPa, 473 K, 12 h), was found for Cu-BTC only.KEYWORDS: Metal organic frameworks (MOFs), CO 2 capture, Adsorption mechanism, X-ray absorption fine structure (XAFS), physical and chemical transformations.

Adsorption of Malachite Green and Alizarin Red S Dyes Using Fe-BTC Metal Organic Framework as Adsorbent

“…Figure 1 a shows the XRD pattern of the synthesized Fe-BTC MOF. The pattern is well resolved with peaks at 2Ɵ = 11°, 19°, 24°, 28° and 34°, in agreement with the literature reports for Fe-BTC MOF [ 42 , 43 ]. The surface area and pore size distribution were obtained by N 2 adsorption/desorption isotherms ( Figure 1 b), using the Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods.…”

Metal Organic Framework Based Polymer Mixed Matrix Membranes: Review on Applications in Water Purification

“…F300 (also named FE-BTC) is a crystalline solid material with 1,3,5-benzenetricarboxylic acid as the organic linker [120], a pore size of 22 Å and specific surface area of 1500 m 2 /g. F300 was employed in the separation of small organic compounds in the aqueous phase and it has high catalytic activity for a wide variety of Lewis acidity reactions [121]. A100, which has properties similar to MIL-53, is formed by the coordination between Al 3+ and the nodal metal atom and 1,4-benzenedicarboxylic acid.…”

Performance of Mixed Matrix Membranes Containing Porous Two-Dimensional (2D) and Three-Dimensional (3D) Fillers for CO2 Separation: A Review

“…The presence of unsaturated open metal sites in Cu-based MOFs after activation is reported as an assisted mechanism in CO 2 sorption [ 93 ]. Comparison of the CO 2 adsorption capacity of two well-known MOFs containing the same ligand in their framework (Cu-BTC and Fe-BTC) showed that the Cu-BTC is characterized by a much larger CO 2 uptake (73.2 cm 3 g –1 , at room temperature and atmospheric pressure) when compared to the Fe-BTC (15.9 cm 3 g –1 ) [ 94 ]. The results clearly pointed out the higher CO 2 affinity and interaction of Cu ions together with open metal sites, making Cu-based MOFs interesting for the fabrication of mixed matrix membranes for CO 2 separation.…”