A robust viologen and Mn-based porous coordination polymer with two types of Lewis acid sites providing high affinity for H2O, CO2 and NH3.

A novel porous coordination polymer [Mn(pc3)(H2O)2]·xH2O (3 < x < 4) is synthesized in water at pH = 7 using the anionic viologen-carboxylate ligand 4,4'-bipyridinium,1,1'-bis-(2,4-dicarboxyphenyl) (pc32-). Dehydration of the material results in the formation of open pores containing two types of accessible Lewis acid sites: exposed Mn2+ cations and N+ atoms of viologen units. Due to this property the PCP shows high affinity and capacity in the adsorption of H2O, CO2 and NH3. Despite the presence of strong adsorption sites this material is stable in liquid water and in gaseous NH3.

Characterization of adsorbed water in MIL-53(Al) by FTIR spectroscopy and ab-initio calculations.

Here, we report ab-initio calculations developed with a twofold purpose: understand how adsorbed water molecules alter the infrared spectrum of the metal-organic framework MIL-53(Al) and to investigate which are the associated physico-chemical processes. The analyzed structures are the two anhydrous narrow (np⊘) and large (lp⊘) pore forms and the hydrated narrow pore form (np-H2O) of the MIL-53(Al). For these structures, we determined their corresponding infrared spectra (FTIR) and we identified the vibrational modes associated to the dominant spectral lines. We show that wagging and scissoring modes of CO2 give flexibility to the structure for facilitating the lp⊘- np⊘ transition. In our studies, this transition is identified by eight vibrational modes including the δCH(18a) vibrational mode currently used to identify the mentioned transition. We report an exhaustive band identification of the infrared spectra associated to the analyzed structures. Moreover, the FTIR for the np-H2O structure allowed us to identify four types of water molecules linked to the host structure by one to three hydrogen bonds.

Spectroscopic signatures of VOC physisorption on microporous solids. Application for trichloroethylene and tetrachloroethylene adsorption on MFI zeolites.

This paper presents an experimental infrared spectroscopic study of the physisorption of trichloroethylene (TCE) and tetrachloroethylene (PCE) on a self-supported high silica ZSM5 zeolite. The evolution of the shape, area, and location of vibration bands of both the adsorbent and the adsorbate is analyzed with respect to the number of sorbed molecules. The state of the adsorbed phase is characterized upon adsorption by comparing the location of the investigated vibration bands with the location of the corresponding vibration bands of the chloroalkenes in gaseous, liquid, and solid phases. The singular behavior of PCE with respect to TCE is seen from the modification of vibration bands of both the adsorbed phase and the adsorbent upon loading. The adsorption process proceeds by stages for PCE, whereas it appears continuous for TCE. Particular micropore loadings are evidenced at 4 and 6.5 molec.uc(-1) for PCE and at 6 molec.uc(-1) for TCE, in agreement with previous macroscopic and microscopic data. In addition, the presence of admolecules induces at least one emerging vibration band located at around 1715 cm(-1), mainly due to a contribution of the microporous surface of the adsorbent.

Adsorption of water vapor by poly(styrenesulfonic acid), sodium salt: isothermal and isobaric adsorption equilibria.

Air conditioning and dehumidifying systems based on sorption on solids are of great interest, especially in humid climates, because they allow reduction of thermal loads and use of chlorofluorocarbons. Previous studies have shown that hydrophilic polymers such as sulfonic polymers can have very high performance in water adsorption from air. The aim of this study was to characterize the water vapor adsorption properties of fully sulfonated and monosulfonated poly(styrenesulfonic acid), sodium salt, and to elucidate the mechanism of adsorption on these materials. Adsorption isotherms have been determined by TGA between 298 and 317 K for pressures ranging from 0.1 to 45 hPa. They have type II of the IUPAC classification and a small hysteresis loop between adsorption and desorption processes was observed only for the monosulfonated sample. Water content is up to 80% weight at 80% relative humidity. Adsorption isotherms have been well fitted with the FHH model. Adsorption-desorption isobars have been determined by TGA under 37 hPa in the temperature range 298-373 K. They show that these polymers can be completely regenerated by heating at 313 K under humidified air. No degradation of the adsorption properties has been observed after several regenerations. Adsorption enthalpies and entropies have been deduced from the Clapeyron equation and from DSC measurements. A good agreement was found. A mechanism of adsorption is proposed considering two kinds of adsorbate: bounded water in electrostatic interaction with functional groups and free water resulting from condensation.