Alkaline-earth metal-based MOF has many merits such as light weight, environmental friendliness and low cost, but it has rarely been used in energy storage and capacitive deionization (CDI). This paper presents a facile method for the fast synthesis of small-size magnesium formate MOF (Mg-MOF) under mild conditions by linker-free incubation in the presence of Mg(CH 3 COO) 2 ⋅ 4H 2 O and dimethylformamide. The formic acid was in situ formed as ligand to facilitate the formation of Mg-MOF. The effect of incubation time on the morphology of MOF crystals was investigated. The small and well-defined Mg-MOF particles with the size of ~ 18 nm were formed in 1 h incubation, characterized by scanning electron microscopy and X-ray diffraction. Following carbonization, the Mg-MOF-derived mesoporous carbon was obtained. N 2 -sorption isotherm confirmed the mesoporous structure. Cyclic voltammetry test indicated the good electric double-layer feature of the Mg-MOF-derived carbon electrode, and the impedance results showed the excellent conductivity. As a capacitor electrode material, it delivered the specific capacitances of 102 F/g by GCD (0.2 A/g). The Mg-MOF-derived carbon electrode was applied successfully for capacitive deionization (CDI) with a desalination capacity of 8.0 mg/g in a CDI device. A supper fast desalination rate of 1.1 mg/g/min was achieved due to the abundant mesoporous structure. The work provides a cost effective and environmentally friendly way for the synthesis of MOF-based carbon materials free of transition metal, and the prospects for CDI application have been demonstrated.
A magnesium-based metal-organic framework with high hydrothermal stability, Mg-CUK-1, was investigated for the adsorption separation of acetylene from ethylene. The synthesized MOF remained excellent thermostability even near 500 °C according to TGA results. Characterization techniques including FTIR, SEM, and PXRD were utilized to confirm the detailed structure and properties of the Mg-based MOF. It exhibited moderate adsorption capacities of C 2 H 2 (3.01 mmol/g at 100 kPa and 273 K). Moreover, it showed preferential adsorption of C 2 H 2 over C 2 H 4 with C 2 H 2 /C 2 H 4 adsorption selectivity over 3, outperforming some popular MOFs. Furthermore, the isosteric heat of C 2 H 2 (<21 kJ/mol) and C 2 H 4 (<18 kJ/mol) were extremely lower than those MOFs with open metal sites. From an industrial point of view, this MOF could be synthesized in absence of organic solvent, drastically reducing the risk of environmental pollution in the production process. Besides, such advantages as excellent hydrothermal stability, cheap and non-poisonous metal ion resource, high C 2 H 2 adsorption capacity, and low isosteric heat make the Mg-based MOF promising in practical application.
Guanhua Zhang,Shaocong Mo,Xiaowei Liao,Feng Liu,Hongtao Xu,Wei Lu
Metal-organic frameworks (MOFs) are interesting materials for carbon dioxide (CO 2 ) adsorption. Herein, novel nanocomposite materials comprising activated carbon (AC) and Magnesium-MOF-74 were synthesized by impregnating different loading ratios of activated carbon into synthesized Magnesium-MOF-74 to yield Magnesium-MOF-74@AC-X (where X represents the Magnesium/AC ratio set to 1:2, 1:1, and 2:1). Compared to Magnesium-MOF-74 alone, Magnesium-MOF-74@AC-X exhibited higher specific surface area, superior thermal stability, elevated CO2 adsorption capacity, and better adsorption selectivity. At 273 K, the adsorption of CO 2 by Magnesium-MOF-74@AC sample containing Magnesium to AC ratio of 1:2 reached 40.31 cm 3 /g, while that of pristine Magnesium-MOF-74 was only 21.01 cm 3 /g. At 298 K, the adsorption capacity reached 29.45 cm 3 /g, while that of pristine Magnesium-MOF-74 was 1.91-fold lower. The linear fitting of the adsorption isotherms of composite in the Henry adsorption region using Henry’s law yielded a CO 2 /N 2 selectivity adsorption capacity of 32.19, a value 4.55-fold higher than pristine Magnesium-MOF-74.
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