Abstract
Non-porous zinc/cobalt azolate frameworks with diamond-type crystal structure (MAF–31/ZIF–D–CoM) have been synthesized in large scale with an acid-catalyzed process. Afterward, an ethanol exposure process was applied for 1, 7, and 14 days to transform MAF–31/ZIF–D–CoM into porous T–MAF–4/T–ZIF–67. Two porous zinc/cobalt azolate frameworks standards (MAF–4/ZIF–67) with sodalite-type crystal structures were prepared with a solvent-free method for comparison with T–MAF–4/T–ZIF–67. Effects of ethanol vapor exposure on structual transformation of MAF–31/ZIF–D–CoM were characterized throughly. Obvious structural transfomations between non-porous and porous zinc/cobalt azolate frameworks were found with X–ray diffraction (XRD), Field–emission scanning electron microscope (FE–SEM), and X–ray absorption near-edge structure/extended X–ray absorption fine structure (XANES/EXAFS) spectra. After the 14-day ethanol vapor exposure, the CO2 adsorption uptakes of MAF–31 and ZIF–D–CoM in low/high pressures were enhanced from 5.18 × 10−5/0.68 and 1.20 × 10−4/0.18 to 1.76 × 10−3/8.27 and 1.99 × 10−3/11.2 mmol/g, respectively. The CO2 selectivities of MAF–31/ZIF–D–CoM were also improved from 0.29/2.34 to 6.33/16.47. In addition, CO2 adsorption over zinc/cobalt azolate frameworks obeyed both Langmuir/Freundlich adsorption isotherm models with good agreements.
Published Version
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