Search

A metal–organic framework obtained from a flexible organic linker shows a breathing phenomenon upon adsorption of saturated hydrocarbons. [ABSTRACT FROM AUTHOR]

Abstract: Adsorption of CO2 on dehydrated Prussian blue analogue CoII 3[CoIII(CN)6]2 was studied using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). An infrared peak at 2340cm−1 assigned to adsorbed CO2 was identified and used semi-quantitatively to construct an isotherm at 298K that followed the Langmuir–Freundlich equation in the low-coverage Henry''s law limit with CO2 pressure below about 25kPa. Temperature-dependence at 6.8kPa CO2 was used to determine ΔH ad =−23±3kJmol−1, in this limit as well. Deviation from the Langmuir–Freundlich model was significant at temperatures above 298K and attributed primarily to a loss of reliability of the DRIFT spectra at higher CO2 pressures, particularly at higher temperatures, and the accompanying uncertainties in the difference spectra when correcting for the presence of gaseous CO2. Based on this work, the application of DRIFTS to study CO2 adsorption on Prussian blue analogues and other adsorbents is promising, although the range of conditions over which it can be applied appears to be more limited than with other techniques. [Copyright &y& Elsevier]

Adsorption isotherms of pure gases present in flue gas including CO2, N2, SO2, NO, H2S, and water were studied using prussian blues of chemical formula M3[Co(CN)6]2∙nH2O (M = Co, Zn) using an HPVA-100 volumetric gas analyzer and other spectroscopic methods. All the samples were characterized, and the microporous nature of the samples was studied using the BET isotherm. These materials adsorbed 8-10 wt % of CO2 at room temperature and 1 bar of pressure with heats of adsorpiton ranging from 200 to 300 BtuIlb of CO2, which is lower than monoethanolamine (750 Btuilb of CO2) at the same mass loading. At high pressures (30 bar and 298 K), these materials adsorbed approximately 20-30 wt % of CO2, which corresponds to 3 to 5 molecules of CO2 per formula unit. Similar gas adsorption isotherms for SO2, H2S, and NO were collected using a specially constructed volumetric gas analyzer. At close to 1 bar of equilibrium pressure, these materials sorb around 2.5, 2.7, and 1.2 mmol/g of SO2, H2S, and NO. In particular, the uptake of SO2 and H2S in Co3[Co(CN)6]2 is quite significant since it sorbs around 10 and 4.5 wt % at 0.1 bar of pressure. The stability of prussian blues before and after trace gases was studied using a powder X-ray diffraction instrument, which confirms these materials do not decompose after exposure to trace gases. [ABSTRACT FROM AUTHOR]