Abstract
This paper reports on the comparison of three zirconium-based metal organic frameworks (MOFs) for the capture of carbon dioxide and ethanol vapour at ambient conditions. In terms of efficiency, two parameters were evaluated by experimental and modeling means, namely the nature of the ligands and the size of the cavities. We demonstrated that amongst three Zr-based MOFs, MIP-202 has the highest affinity for CO2 (−50 kJ·mol−1 at low coverage against around −20 kJ·mol−1 for MOF-801 and Muc Zr MOF), which could be related to the presence of amino functions borne by its aspartic acid ligands as well as the presence of extra-framework anions. On the other side, regardless of the ligand size, these three materials were able to adsorb similar amounts of carbon dioxide at 1 atm (between 2 and 2.5 µmol·m−2 at 298 K). These experimental findings were consistent with modeling studies, despite chemisorption effects, which could not be taken into consideration by classical Monte Carlo simulations. Ethanol adsorption confirmed these results, higher enthalpies being found at low coverage for the three materials because of stronger van der Waals interactions. Two distinct sorption processes were proposed in the case of MIP-202 to explain the shape of the enthalpic profiles.
Highlights
In recent decades, the consumption of fossil fuels has increased alarmingly to meet world population needs, in terms of economy and industry
A majority of these products have been designated as factual air pollutants [3,4,5], knowing that the Health Effects Institute has plainly designated air pollution as the fifth risk factor for mortality in the world in 2019 [6]. To solve these environmental issues, it is important to find appropriate techniques for capturing CO2 and volatile organic compounds that can be beneficial in agriculture and industry [7]
We have shown that polarisable molecules such as carbon dioxide and ethanol can be adsorbed by microporous zirconium-based metal organic frameworks (MOFs)
Summary
The consumption of fossil fuels has increased alarmingly to meet world population needs, in terms of economy and industry. IInn tteerrmmss ooff tthheeoorreettiiccaall aaddssoorrbbeedd aammoouunnttss,, MOFF--880011eexxhhibibitistsa aslisglhigtlhytlbyetbterttseorrpsotiropnticoanpaccaiptya,cciotym, pcaormedptaoreMdIPto-20M2I,Pw-2h0ic2h, wishcicohnsisisctoenstiswteitnht wthiethstihmeilsaimr tilhaerotrheetoicraeltipcaolrpeovroelvuomluems e(0s.3(02.3c2mc3m/3g/gffoorr MMOF-801 aanndd 0.27 cm3/g for MIP-202 This is consistent with the difference observed in terms of specific surface areas of these two materials. In the case of MIP-202, the decrease in the heat of adsorption is very moderate compared to the other materials This behavior could be attributed to the interaction between CO2 and amino functions or extra-framework anions, which would be a prominent sorption process, up to θ = ~0.4 where the isosteric curves become parallel. In MIP-202, the presence of extra-framework anions (Cl−) illustrated in the literature should be considered as important adsorption sites if available [44] Such conclusions can be supported by the snapshots obtained from Monte Carlo simulations and corresponding to the most probable positions of guest molecules in the pores (see Figure S4). Confinement effects decrease for larger pores, explaining the lowest value found for this material [50,51]
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