Abstract

The widespread emissions of toxic gases from fossil fuel combustion represent major welfare risks. Here we report the improvement of the selective sulfur dioxide capture from flue gas emissions of isoreticular nickel pyrazolate metal organic frameworks through the sequential introduction of missing-linker defects and extra-framework barium cations. The results and feasibility of the defect pore engineering carried out are quantified through a combination of dynamic adsorption experiments, X-ray diffraction, electron microscopy and density functional theory calculations. The increased sulfur dioxide adsorption capacities and energies as well as the sulfur dioxide/carbon dioxide partition coefficients values of defective materials compared to original non-defective ones are related to the missing linkers enhanced pore accessibility and to the specificity of sulfur dioxide interactions with crystal defect sites. The selective sulfur dioxide adsorption on defects indicates the potential of fine-tuning the functional properties of metal organic frameworks through the deliberate creation of defects.

Highlights

  • Since the first two molecules have such high adsorption energies, we studied the adsorption of a third molecule, which does not interact with the cation (Supplementary Fig. 14) giving rise to a much lower binding energy ( À 42.0 kJ mol À 1), which suggests that the third molecule is not chemisorbed but physisorbed

  • It should be noted that all the measurements were done on the materials after SO2 chemisorption to ensure the thermodynamic equilibrium

  • The zero-coverage thermodynamic parameters of the adsorption process for SO2 and CO2 are gathered in Table 1 and Supplementary Table 4, respectively

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Summary

Introduction

Gas-phase adsorption at zero-coverage surface was studied using the pulse chromatographic technique[35] employing a gas chromatograph and stainless steel 20 cm-column (0.4 cm internal diameter) packed with ca. The zero-coverage thermodynamic parameters of the adsorption process for SO2 and CO2 are gathered in Table 1 and Supplementary Table 4, respectively. These values were calculated using a van’t Hoff type analysis employing isothermal chromatographic measurements[5]. The retention volumes were corrected taking into account the volume expansion of the gas entering the capillary due to the temperature increase according to VS 1⁄4 (tR À tm)Fa(T/Ta)j where VS 1⁄4 net retention volume (ml); tR 1⁄4 retention time (min); tm 1⁄4 dead time (min); Fa 1⁄4 volumetric flow-rate measures at ambient temperature (ml min À 1); T 1⁄4 column temperature (K); Ta 1⁄4 ambient temperature (K); the James–Martin gas compressibility correction j 1⁄4 (3(pi/p0)[2] À 1)/(2(pi/p0)[3] À 1) where pi 1⁄4 pressure of gas applied to the chromatogram and p0 1⁄4 pressure of gas at out

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