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.

New low-temperature preparations of some simple and mixed co and ni dispersed sulfides and their chemical behavior in reducing atmosphere.

A series of simple (CoS(2), Co(9)S(8), NiS(2), NiS, Ni(3)S(2)) and mixed sulfides (NiCo(2)S(4), Ni(0.33)Co(0.67)S(2), Ni(3)Co(6)S(8), CuCo(2)S(4), Cu(0.33)Co(0.67)S(2)) was prepared using low-temperature procedures. To obtain the mixed sulfides, the mixtures of the solutions of the corresponding salts were precipitated by Na(2)S and then heated in a sulfiding atmosphere at 300 degrees C. It has been found that the product phase composition depends on the sulfiding atmosphere. Using a H(2)S/Ar mixture leads to pyrite type sulfides, whereas treatment in H(2)S/H(2) flow allowed the preparation of Ni-Co and Cu-Co thiospinels. The as prepared highly dispersed single-phase materials were characterized by X-ray powder diffraction, scanning electron microscopy, temperature-programmed reduction (TPR), elemental analysis, and BET surface area measurements.