Abstract
A greener route to synthesize mesoporous copper–gallic acid metal–organic framework (CuGA MOF) than the conventional method using harmful DMF solvent was proposed in this study. Various synthesis attempts were conducted by modifying the synthesis conditions to produce CuGA MOF with comparable physical properties to a reference material (DMF-synthesized CuGA NMOF). The independent variables investigated include the molar ratio of NaOH to GA (1.1 to 4.4) and the synthesis temperature (30, 60, 90 °C). It was found that proper NaOH addition was crucial for suppressing the generation of copper oxide while maximizing the formation of CuGA MOF. On the other hand, the reaction temperature mainly affected the stability and adsorption potential of CuGA MOF. Reacting Cu, GA, and NaOH at a molar ratio of 1:1:2.2 and a temperature of 90 °C, produced mesoporous MOF (CuGA 90–2.2) with a surface area of 198.22 m2/g, a pore diameter of 8.6 nm, and a thermal stability of 219 °C. This MOF exhibited an excellent adsorption capacity for the removal of methylene blue (124.64 mg/g) and congo red (344.54 mg/g). The potential usage of CuGA 90–2.2 as a reusable adsorbent was demonstrated by its high adsorption efficiency (> 90%) after 5 adsorption–desorption cycles.
Highlights
A greener route to synthesize mesoporous copper–gallic acid metal–organic framework (CuGA metal–organic frameworks (MOFs)) than the conventional method using harmful DMF solvent was proposed in this study
The synthesized CuGA MOF samples were designated as CuGA T-X; with T refers to the synthesis temperature, and X refers to the molar ratio of NaOH to GA
The formation of C u2O can be attributed to the oxidation activity that occurs due to the presence of excessive NaOH24. These results suggest that X = 2.2 is the most suitable NaOH to GA molar ratio for the synthesis of CuGA MOF, and this NaOH concentration was chosen for further studies
Summary
A greener route to synthesize mesoporous copper–gallic acid metal–organic framework (CuGA MOF) than the conventional method using harmful DMF solvent was proposed in this study. Reacting Cu, GA, and NaOH at a molar ratio of 1:1:2.2 and a temperature of 90 °C, produced mesoporous MOF (CuGA 90–2.2) with a surface area of 198.22 m2/g, a pore diameter of 8.6 nm, and a thermal stability of 219 °C. This MOF exhibited an excellent adsorption capacity for the removal of methylene blue (124.64 mg/g) and congo red (344.54 mg/g). Adsorption is a favorable approach due to its low energy consumption and processing cost, safer by-product, and simple regeneration techniques[9,10] It triggers researches on the development of various adsorbent material with efficient dye removal ability. The effect of synthesis temperature on the adsorption ability of the CuGA MOFs was highlighted and the reusability of CuGA MOF for the removal of CR and MB was assessed in this study
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