The adsorption of cytochrome c onto different mesoporous molecular sieves (C 12 -MCM-41, C 16 -MCM-41 and SBA-15) is studied at different solution pHs. Adsorption isotherms were recorded up to final solution concentrations of ca. 250 µmol/L and were found to be of the pseudo-Langmuir type. Cytochrome c (cyt c) adsorption was observed to be pH-dependent with maximum adsorption near the isoelectric point of the protein. SBA-15 showed a larger amount of cyt c adsorption as compared to MCM-41. The increased cyt c adsorption capacity may be due to the larger pore volume and pore diameter as compared to C 12 -and C 16 -MCM-41. It has been discovered that the amount of cyt c adsorption can be increased by the introduction of aluminum into the pure silica materials. The observed increase is most likely a consequence of the strong electrostatic interaction between the negative charges on the aluminum sites and the positively charged amino acid residues of cyt c. Furthermore, the rate of cyt c adsorption has been studied and no significant differences in adsorption rate were found for the mesoporous materials with different pore diameters between 3 and 9 nm. While the adsorption capacity is reduced upon bead formation (due to the reduction in specific pore volume), the rate of adsorption is mainly unchanged.

The metal organic framework material Cu3(BTC)2 (BTC = 1,3,5-benzenetricarboxylate) has been synthesized using different routes: under solvothermal conditions in an autoclave, under atmospheric pressure and reflux, and by electrochemical reaction. Although the compounds display similar structural properties as evident from the powder X-ray diffraction (XRD) patterns, they differ largely in specific surface area and total pore volume. Thermogravimetric and chemical analysis support the assumption that pore blocking due to trimesic acid and/or methyltributylammoniummethylsulfate (MTBS) which has been captured in the pore system during reaction is a major problem for the electrochemically synthesized samples. Isobutane and isobutene adsorption has been studied for all samples at different temperatures in order to check the potential of Cu3(BTC)2 for the separation of small hydrocarbons. While the isobutene adsorption isotherms are of type I according to the IUPAC classification, the shape of the isobutane isotherm is markedly different and closer to type V. Adsorption experiments at different temperatures show that a somewhat higher amount of isobutene is adsorbed as compared to isobutane. Nevertheless, the differential enthalpies of adsorption are only different by about 5 kJ/mol, indicating that a strong interaction between the copper centers and isobutene does not drive the observed differences in adsorption capacity. The calculated breakthrough curves of isobutene and isobutane reveal that a low pressure separation is preferred due to the peculiar shape of the isobutane adsorption isotherms. This has been confirmed by preliminary breakthrough experiments using an equimolar mixture of isobutane and isobutene.

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