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A method based on the deconvolution of TPD spectra is proposed for the characterization of surface oxygen groups, which can act as the active sites on carbon catalysts. The method, which was previously used to characterize activated carbons oxidized in the gas phase, has been extended and applied to other materials, carbons oxidized in the liquid phase. It is shown that this method fits quite well the TPD experimental data of the original activated carbon as well as the gas-phase and liquid-phase oxidized materials and is suitable to estimate the amounts of each type of oxygen surface groups.

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A copper(II) Schiff base complex bearing hydroxyl groups [bis(4-hydroxysalicylaldehyde)ethylenediaminate] copper(II), [Cu(4-HOsalen)], was directly anchored onto an air-oxidized activated carbon. Oxidation of the activated carbon was done with a mixture of air and N2 (with 5% O2) to increase the oxygenated surface functional groups, and complex immobilization was made by attachment of the metal complex hydroxyl groups to carbon surface groups. The adsorption/desorption of the metal complexes onto the oxidized activated carbon was monitored by UV-vis spectroscopy. Carbon-based materials were characterized by elemental analysis, surface techniques (scanning electron microscopy and X-ray photoelectron microscopy), nitrogen adsorption isotherms, and thermal analysis (temperature-programmed desorption and thermogravimetry). EPR spectra of both free and carbon-supported [Cu(4-HOsalen)] complexes were recorded. A comparative study with the unfunctionalized copper complex, [Cu(salen)], was also performed to assess the role of the hydroxyl groups in copper complex anchorage. Data from all the techniques have provided evidence that copper complexes with the hydroxyl functionalized Schiff base are chemically bound to carbon surface groups through the ligand substituent, whereas the unfunctionalized complex, [Cu(salen)], was only physically adsorbed onto the activated carbon and was leached during Soxhlet extraction.

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Copper(II) acetylacetonate was anchored onto a triamine functionalised activated carbon by Schiff condensation using a four‐step procedure: (i) oxidation of activated carbon with nitric acid; (ii) treatment with thionyl chloride to convert carbon surface carboxylic acids into acyl chlorides; (iii) condensation of acyl chloride functionalities with amine groups of bis(3‐aminopropyl)amine (trien); and (iv) Schiff condensation between free amine groups of bound trien with the oxygen atoms of acetylacetonate coordinated to the copper(II) ion. The same complex was also anchored to the unmodified activated carbon and to the acyl chloride functionalised carbon prepared in (ii). The resulting carbon‐based materials were characterised by elemental analysis, surface techniques (SEM and XPS), temperature programmed desorption, and nitrogen adsorption at 77 K and EPR spectroscopy for the materials with copper(II) complexes. Data from all techniques provided evidence for (i) the covalent binding of trien to acyl chloride functionalities; and (ii) the irreversible attachment of [Cu(acac)2] to all carbon‐based materials. Data for the materials with copper(II) proved conclusively that only the immobilisation procedure based on Schiff condensation with trien led to copper(II) complexes in which the metal centre remains four‐coordinate. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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