Metalloporphyrin-containing mesoporous materials, named VTPP@SBA, were prepared via a simple anchoring of vanadyl porphyrin (5,10,15,20-Tetraphenyl-21H,23H-porphine vanadium(IV) oxide) through a SBA-15-type mesoporous material. For comparison, vanadyl porphyrin was also impregnated on SiO2 (VTPP/SiO2). The characterization results of catalysts by XRD, FTIR, DR-UV-vis, and EPR confirm the incorporation of vanadyl porphyrin within the mesoporous SBA-15. These catalysts have also been studied using electrochemical and photoelectrochemical methods. Impedance measurements confirmed that supporting the porphyrin in silica improved the electrical conductivity of samples. In fact, when using mesoporous silica, current densities associated with oxidation/reduction processes appreciably increased, implying an enhancement in charge transfer processes and, therefore, in electrochemical performance. All samples presented n-type semiconductivity and provided an interesting photoelectrocatalytic response upon illumination, especially silica-supported porphyrins. This is the first time that V-porphyrin-derived materials have been tested for photoelectrochemical applications, showing good potential for this use.

A simple and environmentally friendly method, based on sequential adsorption of polyacrylamide (PAM) and transition metal ions (Pd 2+ , Ag + ) on zinc oxide precipitated from water solution, was used to synthesize supported mono-and bimetallic catalysts with various Pd:Ag ratios. The catalyst characterization results indicated that PAM and metal ions are completely adsorbed by zinc oxide, forming polymer-stabilized Pd and Ag nanoparticles of 1-3 nm in size, evenly distributed on the support surface. The catalysts were studied in the hydrogenation of phenylacetylene under mild conditions (0.1 MPa, 40°C). Although Ag-free 1%Pd-PAM/ZnO catalyst presents an interesting catalytic performance (in terms of activity and selectivity), the optimal catalyst was 1%Pd-Ag(3:1)-PAM/ZnO, presenting a selectivity to styrene of 88% at 85.4% conversion of phenylacetylene. For comparison, similar Pd-Ag (3:1) bimetallic catalysts modified with polysaccharides such as pectin (Pec), chitosan (Chit) and 2-hydroxyethylcellulose (HEC) were studied in the hydrogenation process. The catalysts demonstrated nearly the same selectivity to styrene. The activity of the catalysts decreases in the following order: 1%Pd-Ag(3:1)-HEC/ZnO > 1%Pd-Ag(3:1)-PAM/ZnO > 1%Pd-Ag(3:1)-Pec/ZnO > 1%Pd-Ag(3:1)-Chit/ZnO.