Two new isostructural porous supramolecular materials {[Cu 2 (amp) 4 Cl][M(C 2 O 4 ) 3 ]•6H 2 O} n (amp = 2-aminomethylpyridine), designated as II and III for M = Cr(III) and M = Fe(III) respectively, have been synthesized by a self-assembly process of two ionic complexes [Cu 2 (amp) 4 Cl] 3+ and [M(C 2 O 4 ) 3 ] 3− , M = Fe(III) and Cr(III). They build heterometallic hydrogenbonded-, oxalato-and chlorido-bridged zigzag chains with interchain hydrogen bonds and π−π interactions. This results in supramolecular potentially porous architectures exhibiting large channels filled with hexameric water clusters. Their activated phases, II′ and III′, can readsorb the water molecules to regenerate the initial materials which are stable for many water adsorption and desorption cycles like that of their homologous catena-{ [(Co(amp) 3 ][Cr(C 2 O 4 ) 3 ]•6H 2 O} (I′). The three materials I′, II′, and III′ exhibit water adsorption and desorption isotherms having a sigmoidal shape and resulting in the combination of a type I(b) profile followed by an S-shaped type V isotherm with hysteresis. At 20 °C, the steep water sorption of the S-shaped isotherm occurs at 0.1P/P 0 for II′ and III′. This water sorption behavior is quite different from the related compound I′, where a gate opening and closure process is involved, giving a type V isotherm with a pronounced H1-type hysteresis loop with parallel and steep adsorption (at 0.25P/P 0 ) and desorption branches (at 0.17P/P 0 ). The water adsorption capacities of the three materials I′, II′, and III′ are 17, 12, and 11 wt %, respectively. Temperature does not have a great effect on their water sorption properties, and they all exclude N 2 and CO 2 gases in the low pressure range. Compounds II′ and III′ are classified among the materials for which the dehumidification and the humidification trigger points are the same or too close (10% relative humidity (r.H.) in their case), while I′ shows a good potential to be used for automatic indoor control in the range of 15−25% r.H. recommended for many activities. All the differences observed in the water sorption properties of the three materials are related to (i) the type of water cluster which is built in each material, (ii) the strength of the hydrogen bonds within each water cluster and between the clusters and its host, and (iii) the strength of the intrahost interactions which keep the pores of the material closed.

The two-dimensional (2-D) catena-{Co­(amp)3Cr­(ox)3­·6H2O}­(amp = 2-picolylamine, ox = oxalate) compound is built by the [Co­(amp)3]3+ (D) and [Cr­(ox)3]3– (A) ions via multiple hydrogen bonds and hosts well-resolved R12 dodecameric discrete water cluster rings between its stacked layers. It undergoes reversible single crystal to single crystal transformation upon dehydration and rehydration in air, both processes being correlated to gradual changes from brown (hydrated phase) to green (dehydrated phase) and vice versa. The water uptake mass of this compound is 0.13 g/g of sample, and the rehydration process needs 90 min. The rate limiting step of the rehydration process is the diffusion of the water molecules into the framework of the dehydrated phase because the latter does not have voids. The 2-D catena-{Co­(amp)3Cr­(ox)3­·6H2O} can undergo many cycles of dehydration/rehydration (breathing) processes without losing its crystallinity. During these processes, its unit cell contracts and expands by 9.39% along the a axis, 12.22% along b, and 2.03% along c for a total volume change of 22.03%. The breakage and formation of some hydrogen bonds in the compound take place alongside the processes, especially along the b axis, which is the main direction of modification of the unit cell. One of these hydrogen bonds is responsible for the modification of the coordination polyhedron around the chromium­(III) ions which becomes less distorted and provokes the gradual thermochromic property observed in this compound.

In this study, a bio-derived precipitating agent/ligand, palm kernel oil, has been used as an alternative route for the green synthesis of nanoparticles of Fe-doped Co3O4 via the co-precipitation reaction. The palm oil was extracted from dried palm kernel seeds by crushing, squeezing and filtration. The reaction of the palm kernel oil with potassium hydroxide, under reflux, yielded a solution containing a mixture of potassium carboxylate and excess hydroxide ions, irrespective of the length of saponification. The as-obtained solution reacts with an aqueous solution containing iron and cobalt ions to yield the desired metallo-organic precursor, iron cobalt carboxylate. Characterization of the precursors by IR and gas chromatography (GC) attests to the presence of carboxylate fatty acids in good agreement with the proportion contained in the oil, and ICP confirms that the metallic ratios are in the proportion used during the synthesis. Analysis of the products thermally decomposed between 400 °C and 600 °C by XRD, EDX, TEM and ToF-SIMS, established that cobalt iron oxide nanoparticles (Co(1−x)Fex)3O4 were obtained for x ≤ 0.2 and a nanocomposite material (Co(1−x)Fex)3O4/Fe3O4 for x ≥ 0.2, with sizes between 22 and 9 nm. ToF-SIMS and XRD provided direct evidence of the progressive substitution of cobalt by iron in the Co3O4 crystal structure for x ≤ 0.2.

The stacked two-dimensional supramolecular compound catena-{Co(amp)3Cr(ox)3·6H2O} (amp = 2-picolylamine, ox = oxalate) has been synthesized from the bimolecular approach using hydrogen bonds. It is built from layers in which both Co(amp)(3+) (D) and Cr(ox)(3-) (A) ions are bonded in a repeating DADADA… pattern along the a and c axes by multiple hydrogen bonds. These layers host a well resolved R12 dodecameric discrete ring of water clusters built by six independent molecules located around the 2c centrosymmetric Wyckoff positions of the P21/n space group in which the compound crystallizes. These clusters are ranged along the [001] direction, occupy 733.5 Å(3) (22.0%) of the unit cell and have a chair conformation via 12 hydrogen bonds. The water molecules of the cluster are linked with stronger hydrogen bonds than those between the cluster and its host, which explains the single continuous step of the dehydration process of the compound.

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