Chitin/Metal-Organic Framework Composites as Wide-Range Adsorbent.

Composites based on chitin (CH) biopolymer and metal-organic framework (MOF) microporous nanoparticles have been developed as broad-scope pollutant absorbent. Detailed characterization of the CH/MOF composites revealed that the MOF nanoparticles interacted through electrostatic forces with the CH matrix, inducing compartmentalization of the CH macropores that led to an overall surface area increase in the composites. This created a micro-, meso-, and macroporous structure that efficiently retained pollutants with a broad spectrum of different chemical natures, charges, and sizes. The unique prospect of this approach is the combination of the chemical diversity of MOFs with the simple processability and biocompatibility of CH that opens application fields beyond water remediation.

Chromium Speciation in Zirconium-Based Metal-Organic Frameworks for Environmental Remediation.

Acute CrVI water pollution due to anthropogenic activities is an increasing worldwide concern. The high toxicity and mobility of CrVI makes it necessary to develop dual adsorbent/ion-reductive materials that are able to capture CrVI and transform it efficiently into the less hazardous CrIII . An accurate description of chromium speciation at the adsorbent/ion-reductive matrix is key to assessing whether CrVI is completely reduced to CrIII , or if its incomplete transformation has led to the stabilization of highly reactive, transient CrV species within the material. With this goal in mind, a dual ultraviolet-visible and electron paramagnetic spectroscopy approach has been applied to determine the chromium speciation within zirconium-based metal-organic frameworks (MOFs). Our findings point out that the generation of defects at Zr-MOFs boosts CrVI adsorption, whilst the presence of reductive groups on the organic linkers play a key role in stabilizing it as isolated and/or clustered CrIII ions.

Encapsulation of ß-alanine model amino-acid in zirconium(IV) metal organic frameworks: Defect engineering to improve host guest interactions.

Metal-Organic Frameworks (MOFs) are porous coordination networks assembled through metal complexes with organic linkers. Due to their chemical versatility, these materials are being investigated for various applications including gas storage and separation, biomedicine and catalysis. The aim of this work is the encapsulation of the model ß-alanine amino-acid in the nanostructured zirconium-based MOF (UiO-66) which contains the ligand H2BDC (1,4-benzenedicaboxylic acid). Additionally, ligand functionalization (by using H2doBDC (2,5-dihydroxy-1,4-benzenedicarboxylic acid) and defect engineering have been carried out to produce UiO-66 derivatives, in order to modify the host-guest interactions, and hence study their influence on the ß-alanine loading capacity and release kinetics. The as-obtained materials have been characterized by X-ray diffraction (XRD), X-ray thermo diffraction (TDX), infrared (IR) spectroscopy, thermogravimetric analysis-differential scanning calorimetry (TG-DSC) and elemental analysis (EA). Morphology of nanoscale MOFs has been explored by transition electron microscopy (TEM). Adsorption isotherms have been constructed, and the concentration of ß-alanine in the post-adsorption solution (supernatant) has been quantified by high performance liquid chromatography coupled with mass spectroscopy (HPLC-MS) and EA. Adsorption capacity values indicate that the presence of hydroxyl groups at the organic linker H2doBDC enhances the host-guess affinity between the framework and the adsorbate ß-alanine. The influence of defect engineering, on the adsorption however, is not that obvious. On the other hand, desorption experiments show similar behaviour for H2doBDC-based derivatives. An adsorption mechanism has been proposed consisting of a combination of host-guest interaction at low concentrations, and covalent anchoring/ligand displacement by ß-alanine at the inorganic clusters.

Exploring new hydrated delta type vanadium oxides for lithium intercalation.

Three hydrated double layered vanadium oxides, namely Na0.35V2O5·0.8(H2O), K0.36(H3O)0.15V2O5 and (NH4)0.37V2O5·0.15(H2O), were obtained by using mild hydrothermal conditions. Their delta type structural frameworks were solved by high-resolution synchrotron X-ray powder diffraction and the interlayer spacings were interpreted from difference Fourier maps. The inter-slab distances are modulated by the water content and the special arrangements of the alkali and ammonium cations. The XPS measurements denote mixed valence systems with high contents of V4+ ions up to 40%. The monitoring of the V4+ EPR signal over time suggests a reduction of the electronic delocalization on account of the partial oxidation to V5+. The electrochemical performance of the active phases is strongly conditioned by the vacuum-drying process of the electrodes, showing better capacity retention when vacuum is not applied. In situ X-ray diffraction shows a structural mechanism of contraction/expansion of the bilayers upon lithium insertion/extraction where the alkali ions behave as structural stabilizers. Galvanostatic cycling at very low current density implies migration of the alkali "pillars" triggering the collapse of the structure.

Structural Transformations in the Thermal Dehydration of [Cu2(bpa)(btec)(H2O)4]n Coordination Polymer.

Reactions between pyridinic ligands such as 1,2-bis(4-pyridyl)ethane (bpa) and transition metal cations are a very widespread technique to produce extended coordination polymers such as Metal-Organic Frameworks. In combination with a second ligand these systems could present different topologies and behaviors. In this context, the use of 1,2,4,5-benzenetetracarboxylic acid (H4btec) gave us a novel 2D compound, [Cu2(bpa)(btec)(H2O)4]n (1), which was prepared by microwave-assisted synthesis and structurally characterized by means of single crystal X-ray diffraction. Its thermal behavior was analyzed through thermogravimetric analysis and variable temperature powder X-ray diffraction, concluding that thermal stability is influenced by the coordination water molecules, allowing two sequential thermochromic phase transformations to take place. These transformations were monitored by electronic paramagnetic resonance spectroscopy and magnetic susceptibility measurements. In addition, the crystal structure of the anhydrous compound [Cu2(bpa)(btec)]n (1.ah) was determined. Finally, a topological study was carried out for the bpa ligand considering all the structures deposited in the Cambridge Structural Databased. More than 1000 structures were analyzed and classified into 17 different topologies, according to the role of the ligand.

Thermal activation of charge carriers in ionic and electronic semiconductor ß-AgIVVO3 and ß-AgIVVO3@VV 1.6VIV 0.4O4.8 composite xerogels.

Silver vanadium oxide (SVO) and Silver Vanadium Oxide/Vanadium Oxide (SVO@VO) composite hydrogels are formed from the self-entanglement of ß-AgVO3 nanoribbons and slightly reduced vanadium oxide (VO) (VV 1.6VIV 0.4O4.8) nanoribbons; respectively. Starting from randomly distributed nanoribbons within hydrogels, and after a controlled drying process, a homogeneous xerogel system containing tuneable SVO : VO ratios from 1 : 0 to 1 : 1 can be obtained. The precise nanoribbons compositional control of these composite system can serve as a tool to tune the electrical properties of the xerogels, as it has been demonstrated in this work by impedance spectroscopy (IS) experiments. Indeed, depending on the composition and temperature conditions, composite xerogels can behave as electronic, protonic or high temperature ionic conductors. In addition, the electric and protonic conductivity of the composite xerogels can be enhanced (until a critical irreversible point), through the temperature triggered charge carrier creation. As concluded from thermogravimetry, IR, UV-Vis and EPR spectroscopy studies, besides the SVO : VO ratio, the thermal induced oxidation/reduction of V5+ to V4+, and thermally triggered release of strongly bonded water molecules at the nanoribbon surface are the two key variables that control the electric and ionic conduction processes within the SVO and composite SVO/VO xerogels.

Double role of metalloporphyrins in catalytic bioinspired supramolecular metal-organic frameworks (SMOFs).

Heterogeneous catalysts are of great interest in many industrial processes for environmental reasons and, during recent years, a great effort has been devoted to obtain metal-organic frameworks (MOFs) with improved catalytic behaviour. Few supramolecular metal-organic frameworks (SMOFs) are stable under ambient conditions and those with anchored catalysts exhibit favourable properties. However, this paper presents an innovative approach that consists of using metal nodes as both structural synthons and catalysts. Regarding the latter, metalloporphyrins are suitable candidates to play both roles simultaneously. In fact, there are a number of papers that report coordination compounds based on metalloporphyrins exhibiting these features. Thus, the aim of this bioinspired work was to obtain stable SMOFs (at room temperature) based on metallo-porphyrins and explore their catalytic activity. This work reports the environmentally friendly microwave-assisted synthesis and characterization of the compound [H(bipy)]2[(MnTPPS)(H2O)2]·2bipy·14H2O (TPPS = meso-tetra-phenyl-porphine-4,4',4'',4'''-tetra-sulfonic acid and bipy = 4,4'-bi-pyridine). This compound is the first example of an MnTPPS-based SMOF, as far as we are aware, and has been structurally and thermally characterized through single-crystal X-ray diffraction, IR spectroscopy, thermogravimetry and transmission electron microscopy. Additionally, this work explores not only the catalytic activity of this compound but also of the compounds µ-O-[FeTCPP]2·16DMF and [CoTPPS0.5(bipy)(H2O)2]·6H2O. The structural features of these supra-molecular materials, with accessible networks and high thermal stability, are responsible for their excellent behaviour as heterogeneous catalysts for different oxidation, condensation (aldol and Knoevenagel) and one-pot cascade reactions.

Open and closed forms of the interpenetrated [Cu2(Tae)(Bpa)2](NO3)2·nH2O: magnetic properties and high pressure CO2/CH4 gas sorption.

Two closed and one open structural forms of the interpenetrated [Cu2(Tae)(Bpa)2](NO3)2·nH2O (H2Tae = 1,1,2,2-tetraacetylethane, Bpa = 1,2-bis(4-pyridyl)ethane) cationic coordination polymer have been synthesized. Three crystallographically related interpenetrated "ths" cationic nets encapsulate water molecules and nitrate anions giving rise to the closed structural forms of [Cu2(Tae)(Bpa)2](NO3)2·nH2O. Depending on the location of water molecules and nitrate groups, two different closed forms with 5.5 and 3.6 crystallization water molecules have been obtained. The thermal activation of the closed structures gives rise to a 29% expansion of the unit cell. This closed to open transformation is reversible, and is triggered by the loss or uptake of solvent. The high pressure gas adsorption experiments show similar selectivity values towards CO2 for CO2/CH4 mixtures to that showed by some metal organic frameworks without unsaturated metal sites, and isosteric heats for CO2 adsorption similar to that for the HKUST-1 compound.

Catalytic Performance of a New 1D Cu(II) Coordination Polymer {Cu(NO3)(H2O)}(HTae)(4,4'-Bpy) for Knoevenagel Condensation.

The {Cu(NO3)(H2O)}(HTae)(4,4'-Bpy) (H2Tae = 1,1,2,2-tetraacetylethane, 4,4'-Bpy = 4,4'-Dipyridyl) 1D coordination polymer has been obtained by slow evaporation. The crystal structure consists of parallel and oblique {Cu(HTae)(4,4'-Bpy)} zig-zag metal-organic chains stacked along the [100] crystallographic direction. Copper(II) ions are in octahedral coordination environment linked to two nitrogen atoms of two bridging 4,4'-Bpy and to two oxygen atoms of one HTae molecule in the equatorial plane. The occupation of the axial positions varies from one copper atom to another, with different combinations of water molecules and nitrate anions, giving rise to a commensurate super-structure. By means of the thermal removal of water molecules, copper coordinatively unsaturated centres are obtained. These open metal sites could act as Lewis acid active sites in several heterogeneous catalytic reactions. The dehydrated compound, CuHTaeBpy_HT, has been tested as a heterogeneous recoverable catalyst for Knoevenagel condensation reactions. The catalyst is active and heterogeneous for the condensation of aldehydes with malononitrile at 60 °C using a molar ratio catalyst:substrate of 3 % and toluene as solvent. The catalyst suffers a partial loss of activity when reusing it, but can be reused at least four times.

Commensurate Superstructure of the {Cu(NO3)(H2O)}(HTae)(Bpy) Coordination Polymer: An Example of 2D Hydrogen-Bonding Networks as Magnetic Exchange Pathway.

The average and commensurate superstructures of the one-dimensional coordination polymer {Cu(NO3)(H2O)}(HTae)(Bpy) (H2Tae = 1,1,2,2-tetraacetylethane, Bpy = 4,4'-bipyridine) were determined by single-crystal X-ray diffraction, and the possible symmetry relations between the space group of the average structure and the superstructure were checked. The crystal structure consists in parallel and oblique {Cu(HTae)(Bpy)} zigzag metal-organic chains stacked along the [100] crystallographic direction. The origin of the fivefold c axis in the commensurate superstructure is ascribed to a commensurate modulation of the coordination environment of the copper atoms. The commensurately ordered nitrate groups and coordinated water molecules establish a two-dimensional hydrogen-bonding network. Moreover, the crystal structure shows a commensurate to incommensurate transition at room temperature. The release of the coordination water molecules destabilizes the crystal framework, and the compound shows an irreversible structure transformation above 100 °C. Despite the loss of crystallinity, the spectroscopic studies indicate that the main building blocks of the crystal framework are retained after the transformation. The hydrogen-bonding network not only plays a crucial role stabilizing the crystal structure but also is an important pathway for magnetic exchange transmission. In fact, the magnetic susceptibility curves indicate that after the loss of coordinated water molecules, and hence the collapse of the hydrogen-bonding network, the weak anti-ferromagnetic coupling observed in the initial compound is broken. The electron paramagnetic resonance spectra are the consequence of the average signals from Cu(II) with different orientations, indicating that the magnetic coupling is effective between them. In fact, X- and Q-band data are reflecting different situations; the X-band spectra show the characteristics of an exchange g-tensor, while the Q-band signals are coming from both the exchange and the molecular g-tensors.

Crystal structure of K0.75[Fe(II) 3.75Fe(III) 1.25(HPO3)6]·0.5H2O, an open-framework iron phosphite with mixed-valent Fe(II)/Fe(III) ions.

Single crystals of the title compound, potassium hexa-phosphito-penta-ferrate(II,III) hemihydrate, K0.75[Fe(II) 3.75Fe(III) 1.25(HPO3)6]·0.5H2O, were grown under mild hydro-thermal conditions. The crystal structure is isotypic with Li1.43[Fe(II) 4.43Fe(III) 0.57(HPO3)6]·1.5H2O and (NH4)2[Fe(II) 5(HPO3)6] and exhibits a [Fe(II) 3.75Fe(III) 1.25(HPO3)6](0.75-) open framework with disordered K(+) (occupancy 3/4) as counter-cations. The anionic framework is based on (001) sheets of two [FeO6] octa-hedra (one with point group symmetry 3.. and one with point group symmetry .2.) linked along [001] through [HPO3](2-) oxoanions. Each sheet is constructed from 12-membered rings of edge-sharing [FeO6] octa-hedra, giving rise to channels with a radius of ca 3.1 Šwhere the K(+) cations and likewise disordered water mol-ecules (occupancy 1/4) are located. O⋯O contacts between the water mol-ecule and framework O atoms of 2.864 (5) Šindicate hydrogen-bonding inter-actions of medium strength. The infrared spectrum of the compound shows vibrational bands typical for phosphite and water groups. The Mössbauer spectrum is in accordance with the presence of Fe(II) and Fe(III) ions.

Heterogeneous catalytic properties of unprecedented µ-O-[FeTCPP]2 dimers (H2TCPP = meso-tetra(4-carboxyphenyl)porphyrin): an unusual superhyperfine EPR structure.

During the past few years, a great deal of effort has been devoted to the anchoring of catalysts into solid coordination networks in order to achieve heterogeneous catalysts. In this sense, an innovative approach consists in using the coordination-network synthons both as structural units and as catalysts. Regarding the latter, metalloporphyrins are suitable candidates for synthons. In fact, a few studies report on coordination compounds based on metalloporphyrins exhibiting these features. On the other hand, highly distorted di-iron oxo dimers containing electron withdrawing groups rank amongst the most effective catalyst models. Thus, the aim of this work was to obtain coordination networks based on iron porphyrins exhibiting those characteristics. In this way, this work reports on the synthesis and characterisation of the µ-O-[FeTCPP]2·16DMF compound (H2TCPP = meso-tetra(4-carboxyphenyl)porphyrin, DMF = N,N-dimethylformamide). This compound is the first example of a µ-oxo dimer with TCPP. The inter-dimer connections give rise to a laminar structure. The structural, spectroscopic and magnetic properties of this compound are consistent with the presence of high-spin Fe(III) ions, exhibiting a strong antiferromagnetic coupling in the µ-oxo dimer (J = -132 cm(-1)). An unusual superhyperfine structure has been observed in EPR that is related to the high accessible volume of the compound. The structural features of the dimers and the accessible network are responsible for the excellent behaviour of the compound as a heterogeneous catalyst for different oxidations of alcohols. Therefore, this compound is one of the very few examples of metalloporphyrins where structural units act as catalysts.

Thermal response, catalytic activity, and color change of the first hybrid vanadate containing Bpe guest molecules.

Four isomorphic compounds with formula [{Co2(H2O)2(Bpe)2}(V4O12)]·4H2O·Bpe, CoBpe 1; [{CoNi(H2O)2(Bpe)2}(V4O12)]·4H2O·Bpe, CoNiBpe 2; [{Co0.6Ni1.4(H2O)2(Bpe)2}(V4O12)]·4H2O·Bpe, NiCoBpe 3; and [{Ni2(H2O)2(Bpe)2}(V4O12)]·4H2O·Bpe, NiBpe 4, have been obtained by hydrothermal synthesis. The crystal structures of CoBpe 1 and NiBpe 4 were determined by single-crystal X-ray diffraction (XRD). The Rietveld refinement of CoNiBpe 2 and NiCoBpe 3 XRD patterns confirms that those are isomorphic. The compounds crystallize in the P1̅ space group, exhibiting a crystal structure constructed from inorganic layers pillared by Bpe ligands. The crystal structure contains intralayer and interlayer channels, in which the crystallization water molecules and Bpe guest molecules, respectively, are located. The solvent molecules establish a hydrogen bonding network with the coordinated water molecules. Thermodiffractometric and thermogravimetric studies showed that the loss of crystallization and coordinated water molecules takes place at different temperatures, giving rise to crystal structure transformations that involve important reduction of the interlayer distance, and strong reduction of crystallinity. The IR, Raman, and UV-vis spectra of the as-synthesized and heated compounds confirm that the structural building blocks and octahedral coordination environment of the metal centers are maintained after the structural transformations. The color change and reversibility of the water molecules uptake/removal were tested showing that the initial color is not completely recovered when the compounds are heated at temperatures higher than 200 °C. The thermal evolution of the magnetic susceptibility indicates one-dimensional antiferromagnetic coupling of the metal centers at high temperatures. For NiCoBpe 3 and NiBpe 4 compounds magnetic ordering is established at low temperatures, as can be judged by the maxima observed in the magnetic susceptibilities. CoNiBpe 2 was proved as catalyst being active for cyanosilylation reactions of aldehydes.

Amine templated open-framework vanadium(III) phosphites with catalytic properties.

Four novel amine templated open-framework vanadium(III) phosphites with the formula (C(5)N(2)H(14))(0.5)[V(H(2)O)(HPO(3))(2)], 1 (C(5)N(2)H(14) = 2-methylpiperazinium), and (L)(4-x)(H(3)O)(x)[V(9)(H(2)O)(6)(HPO(3))(14-y)(HPO(4))(y)(H(2)PO(3))(3-z)(H(2)PO(4))z]·nH(2)O (2, L = cyclopentylammonium, x = 0, y = 3.5, z = 3, n = 0; , L = cyclohexylammonium, x = 1, y = 0, z = 0.6, n = 2.33; , L = cycloheptylammonium, x = 1, y = 0, z = 0, n = 2.33) were synthesized employing solvothermal reactions and characterized by single-crystal X-ray diffraction, ICP-AES and elemental analyses, thermogravimetric and thermodiffractometric analyses, and IR and UV/vis spectroscopy. Single-crystal data indicate that 1 crystallizes in the triclinic system, space group P1, whereas 2, 3 and 4 crystallize in the hexagonal space group P6(3)/m. Compound 1 has a two-dimensional motif with anionic sheets of [V(H(2)O)(HPO(3))(2)](-) formula, whose charge is compensated by the 2-methylpiperazinium cations embedded between the layers. In contrast, 2, 3 and 4 present a pillar-layer network giving rise to a three-dimensional framework containing intersecting 16-ring channels with the primary amine templates and the crystallization water molecules enclosed in them. 1, 2, 3 and 4 behave as heterogeneous catalysts for the selective oxidation of alkyl aryl sulfides, with tert-butylhydroperoxide (TBHP) as the oxidizing agent, being active, selective and recyclable for several successive cycles of reaction.

Synthesis and comparative study of Co(pym)(VO3)2 and [Co(H2O)2(VO3)2]·2H2O.

The three-dimensional Co(pym)(VO(3))(2), 1, hybrid compound, where pym is pyrimidine, has been synthesized under mild hydrothermal conditions at 120 °C. The compound has been characterized by FT-IR spectroscopy, elemental analysis, thermogravimetric measurements, thermodiffractometry, UV-Vis spectroscopy, temperature-dependent magnetic susceptibility and magnetization, and finally a study of specific heat has been performed. The crystal structure of 1 was solved using single-crystal X-ray diffraction data, taking into account that the crystals of this compound are twins of two components. It crystallizes in the monoclinic system, space group C2/c, a = 12.899(5) Å, b = 9.859(2) Å, c = 7.051(1) Å, ß = 111.41(3)°, Z = 4. The crystal structure is built up from edge sharing VO(5) trigonal bipyramid double chains and [CoO(4)pym](n) chains. This resembles the structure of the [Co(H(2)O)(2)(VO(3))(2)]·2H(2)O compound, 2. For this reason a comparative study of their properties was carried out. Magnetic measurements of 1, performed in the 2.0 to 300 K range, reveal the existence of a weak ferromagnetic order near 3 K. This fact was confirmed with magnetization measurements, which show irreversibility characteristic of soft ferromagnets. Magnetic measurements of 2 show a 3D antiferromagnetic ordering at 2.5 K. The magnetization shows a small change of curvature indicating the occurrence of a metamagnetic transition. Specific heat measurements of both compounds confirm the 3D nature of the magnetic order. The comparative study of the magneto-structural correlations reveals that the pyrimidine molecules are responsible for the different magnetic behaviour between 1 and 2.

Flexible and dynamic thermal behavior of self-catenated [{Ni3(H2O)3(Bpa)4}(V6O18)]·8H2O constructed from 10-c heterometallic inorganic-organic clusters.

The hydrothermal treatment of Ni(NO(3))(2)·6H(2)O, NaVO(3), and Bpa (1,2-Di(pyridyl)ethane) (C(12)H(12)N(2)) at 120 °C during 3 days leads to green single crystals of the title compound. The single crystal X-ray diffraction reveals that [{Ni(3)(H(2)O)(3)(Bpa)(4)}(V(6)O(18))]·8H(2)O crystallizes in the monoclinic system, P2(1)/c space group, with a = 13.5536 (2), b = 19.0463 (2), c = 27.7435 (3) Å, ß = 112.3880 (10)°, V = 6622(3) Å(3), with R1(obs) = 0.0558, wR2(obs) = 0.1359, for 10278 observed reflections. The complexity of the crystal structure is based on different points, as the existence of: both "gauche" and "trans" conformations of the organic ligand, the [V(12)O(36)](-12) cycles, formed by 12 corner-sharing VO(4) tetrahedra, and, finally, the combination of both three-dimensional metal-organic and inorganic substructures, giving rise to a self-catenated highly connected net. The crystallization water molecules are semi-encapsulated in the channels along the [100] direction, and their loss gives rise to a dynamical and reversible structural contraction. Moreover, after the removal of the crystallization water molecules, the compound exhibits a negative thermal behavior in the 85-155 °C temperature range, and irreversible structural transformation due to the loss of coordinated water molecules up to 200 °C. The IR and UV-vis spectra were determined for the as-synthesized sample, after the removal of crystallization water molecules and after the irreversible transformation due to the loss of coordinated water molecules. The thermal evolution of χ(m) was adjusted to a magnetic model considering an isotropic dimer plus two Ni(II) d(8) isolated octahedra.

M(C6H16N3)2(VO3)4 as heterogeneous catalysts. Study of three new hybrid vanadates of cobalt(II), nickel(II) and copper(II) with 1-(2-aminoethyl)piperazonium.

Three new hybrid vanadates have been synthesized under hydrothermal conditions with the formula M(C(6)H(16)N(3))(2)(VO(3))(4), where M = Co(II), Ni(II) and Cu(II). The structural analyses show that the phases are isostructural and crystallize in the monoclinic space group P2(1)/c. These compounds show a two-dimensional crystal structure, with sheets composed of [VO(3)](n)(n-) chains and metal centres octahedrally coordinated, chelated by two 1-(2-aminoethyl)piperazonium ligands. The thermal study reveals that the copper containing phase is less stable than the cobalt and nickel containing ones. The IR spectra of the three phases are very similar, with little differences in the inorganic bond region of the copper containing phase. The UV-visible spectra show that the cobalt(II) and the nickel(II) are in slightly distorted octahedral environments. The catalytic tests show that the phases act as heterogeneous catalysts for the selective oxidation of alkyl aryl sulfides, with both H(2)O(2) and tert-butylhydroperoxide as oxidizing agents. The influence of the steric hindrance in the kinetic profile has been studied. The catalytic reactions induce the partial amorphization of the phases.