Green Synthesis of MOF-801(Zr/Ce/Hf) for CO₂/N₂ and CO₂/CH₄ Separation

Abstract

The purification of natural gas and the removal of carbon dioxide from flue gases are crucial to economize precious resources and effectively relieve a series of environmental problems caused by global warming. Metal−organic framework (MOF) materials have demonstrated remarkable performance and benefits in the area of gas separation; however, obtaining materials with high gas capacity and selectivity simultaneously remains difficult. In addition, harsh synthesis conditions and solvent toxicity have been restricted in large-scale production and industrial application. Therefore, MOF-801(Zr/Ce/Hf) was created based on the green synthesis of the MOF-801 construction unit by altering the kinds of metal salts, and the impact of three metal nodes on the performance of gas adsorption and separation was demonstrated by contrasting the three MOFs. The results showed that MOF-801(Ce) has the best CO 2 adsorption capacity (3.3 mmol/g at 298 K), which also was demonstrated with in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results, CO 2 /CH 4 (ideal adsorbed solution theory (IAST) = 13.28 at 298 K, 1 bar, CO 2 /CH 4 = 1:1, v/v), and the separation performance of CO 2 /N 2 (IAST = 57.46 at 298 K, 1 bar, CO 2 /N 2 = 1:1, v/v) among the group. Green synthesis of MOF-801(Zr/Ce/Hf) is an ideal candidate for flue gas separation and methane purification because of its high regeneration capacity and strong cyclic stability.

Icing on the Cake: Imidazole-Anchored Strategy To Enhance the Proton Conductivity of Two Isostructural Ce(IV)/Hf(IV) Metal–Organic Frameworks

“…There is a large cavity between the octahedra formed by the SBU units of MOF-801-Ce (Figure b). Each SBU is coordinated to 12 fumaric acids, and each fumaric acid is bound to 2 SBUs to form a 3D structure with tetrahedral (4.8 and 5.6 Å) and octahedral cages (7.4 Å) (Figure c) showing a fcu topology . Note that the imidazole molecule size is 4.3 × 3.7 Å 2 , so the cavity of MOF-801-Ce can provide enough space to accommodate the imidazole molecule, which proves that it is feasible to encapsulate the imidazole molecule in the MOF pore.…”

“… Its structure is similar to that of UiO-66-Zr/Hf, so it can also be referred to as Ce-UiO-66-fum . It is well-known that MOF-801-Zr is a porous, crystalline, three-dimensional framework constructed from Zr 6 clusters and fumarate linkers that consists of octahedral and tetrahedral pores, and is suitable for gas storage and separation, − sensing, , and more. In addition, it reveals excellent chemical stability, particularly in water, which is a critical attribute for proton conduction applications.…”

Flexible Microporous Framework for One-Step Acquisition of Ethylene from Ternary C2 Hydrocarbons

“…Along with the emergence of porous materials, solid adsorbents are shaping up to replace traditional cryogenic distillation for their lower energy consumption. As porous framework solids, metal–organic frameworks (MOFs), − outshining other crystalline materials such as zeolites and porous carbon materials, − have rapidly emerged as promising adsorbents for gas storage and separation due to their various structures, accurately controllable pore sizes, and functionally permanent porosity. Among them, flexible MOFs can undergo structural transitions in response to external stimuli such as heat, pressure, light, cation/anion exchange, or gas/solvent uptake/removal. , Such stimulus-responsive behaviors enable flexible MOFs to be highly competitive for various applications in gas adsorption and separation, − drug delivery, , and molecular sensing .…”

Computational Simulation of CO2/CH4 Separation on a Three-Dimensional Cd-Based Metal–Organic Framework

“…The engineering design of MOFs for gas separation applications is currently a rapidly growing area of research. − Numerous experimental and simulation-based studies have been documented involving the separation of CO 2 from CH 4 through the use of MOFs. − Considering the quadrupole moment and polarizability of CO 2 , current research efforts to enhance CO 2 uptake and selectivity primarily involves strategies aimed at improving the interaction between CO 2 and the frameworks. These include, but are not limited to, the utilization of various open metal sites, the insertion of functional groups, , the development of smart adsorbents, and ligand shortening in MOFs. , An investigation showed that MOF-801­(Ce) displayed improved separation performance for CO 2 /N 2 and CO 2 /CH 4 compared to MOF-801­(Zr/Hf) . Yu et al conducted experiments to examine the effectiveness of ZU-301, which was functionalized with hydrophobic methyls and high-density oxalate anions in the separation of CO 2 /CH 4 gases.…”

“…81,82 An investigation showed that MOF-801(Ce) displayed improved separation performance for CO 2 /N 2 and CO 2 /CH 4 compared to MOF-801(Zr/Hf). 83 84 In another study, the gas adsorption experimental results demonstrated that the addition of alkaline nitrogen functional groups on the surface of EDA-UiO-66 [where, ethylenediamine (EDA)] resulted in the highest CO 2 adsorption capacity and CO 2 /CH 4 selectivity. This was attributed to the formation of strong quadrupole−dipole interactions between the nitrogen groups and the gas molecules.…”