Na 2 ZrO 3 was synthesized by a solid-state reaction, and a CO 2 chemisorption process was evaluated as a function of temperature to determine whether structural and/or microstructural modifications occurred during the reaction process. This study was performed using the following techniques: thermogravimetry, X-ray diffraction, scanning and transmission electron microscopy, and N 2 adsorption. The results clearly show that Na 2 CO 3 −ZrO 2 was produced on the external shell of Na 2 ZrO 3 during the CO 2 chemisorption process. The microstructural properties varied as a function of temperature. The Na 2 ZrO 3 −CO 2 chemisorption reaction was not limited at T ≤ 550 °C because the Na 2 CO 3 −ZrO 2 external shell contained mesopores. CO 2 diffused through the mesoporous shell, and the reaction continued. Conversely, if the CO 2 chemisorption occurred at T > 550 °C, the mesoporosity on the Na 2 CO 3 −ZrO 2 external shell was not observed, and the chemisorption was kinetically controlled by the diffusion of CO 2 through the sodium crystal phases.

Lithium metazirconate with and without potassium were synthesized by solid-state reaction. Different water vapor sorption experiments were performed in the presence and absence of CO 2 to elucidate the different physicochemical processes produced. In the absence of CO 2 , initial results showed that potassium addition enhances significantly the water sorption on the Li 2 ZrO 3 ceramic. Then, it was shown that water vapor is trapped by two different mechanisms on Li 2 ZrO 3 , adsorption and absorption. When CO 2 was added to water vapor flow the Li 2 ZrO 3 reactivity increased significantly. On the basis of these results, a possible K-Li 2 ZrO 3 -H 2 O-CO 2 reaction mechanism was proposed; as a first step Li 2 ZrO 3 and H 2 O must react producing some Li-OH and Zr-OH species. Then, CO 2 must react with hydroxyl species (mainly Li-OH), producing lithium carbonate. Finally, the presence of this new specie must favor a higher water adsorption.

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Lithium zirconate doped with potassium (K-Li 2 ZrO 3 ) was synthesized by solid-state reaction and then its CO 2 chemisorption capacity was evaluated using different CO 2 -O 2 gas mixtures. These experiments were performed in order to evaluate the effect produced by the O 2 on the kinetic parameters and on the CO 2 absorption reaction mechanism. Although the CO 2 capture dynamic experiments did not show significant variations as a function of the O 2 content, isothermal experiments and their fitting to the Eyring's model did. Different enthalpy activation (∆H q ) values were estimated for the CO 2 chemisorption process, as CO 2 capture is produced by two processes: Initially, the CO 2 chemisorption occurs directly over the K-Li 2 ZrO 3 surface. Then, once a Li 2 CO 3 -ZrO 2 external shell is produced, CO 2 chemisorption is kinetically controlled by diffusion processes, which must imply the lithium and oxygen diffusion. The ∆H q values, of the CO 2 direct chemisorption, increased as a function of the O 2 content. It was explained in terms of a CO 2 -O 2 competition to occupy the Li 2 ZrO 3 surface. On the other hand, the ∆H q values, of the CO 2 chemisorption kinetically controlled by diffusion processes, decreased as a function of the O 2 content. This result confirmed the oxygen diffusion dependency of the CO 2 chemisorption on lithium zirconate.

This study reports the intercalation of pyridine molecules between neighboring layers of two-dimensional (2D) ferrous nitroprusside. In the material under study, the stacking of neighboring layers results in the formation of a long range ordered solid, where the 3D structure is supported by dipoledipole attractive interactions between neighboring pyridine molecules in the interlayer region. No chemical interactions were observed between layers, which preserve their identity as a 2D material. In this hybrid inorganic-organic solid, a thermal induced spin transitions from high to low spin on cooling and [a] 4967 [a] The values of δ are reported relative to sodium nitroprusside at 300 K; The fitting error for δ and Δ is no higher than 0.001 mm/s, and it remains below 0.01 mm/s for the value of Γ; Py =pyridine; LS = low spin; HS = high spin.

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The rehydration process of calcined MgAl-layered double hydroxides (LDHs), with different Mg/Al molar ratios (2.0, 2.5, 3.0, 3.5, and 4.0), was analyzed at different temperatures and relative humidities. Kinetic results clearly showed that LDHs with Mg/Al molar ratios of 2.5 and 3.0 have the fastest H2O absorption. This behavior was attributed to the cations’ structural ordering and to thermodynamic factors. In addition, results allowed obtaining the activation enthalpies for the LDH regeneration of the different samples as a function of the relative humidity. The different activation enthalpies, for each LDH and independently of the Mg/Al molar ratio, showed that the H2O absorption process is more dependent on temperature if the relative humidity is low. Finally, when we analyzed the activation enthalpies as a function of the Mg/Al molar ratio at a defined temperature, their values did not behave linearly. The water absorption process proved to be more dependent on temperature for the LDHs with molar ratios equal to 2.5 and 3.0.

In porous Prussian blue (PB) analogues, the partially naked central metal atoms found at the cavities surface are responsible for many of their physical properties, among them the adsorption potentials. In the as-synthesized PB analogues, such metal sites stabilize water molecules inside the cavity through coordination bond formation. The filling of the cavity volume is completed with water molecules linked to the coordinated ones through hydrogen bonds formation. Vanadyl-based PB analogue shows quite different features. The metal(V) at the cavities surface has saturated its coordination sphere with the O atom of the vanadyl ion (V=O). In this material, the V=O group preserves enough strong dipole moment to stabilize adsorbed species at the cavity through dipole-dipole and dipole-quadrupole in-