resumo
NH2-MIL-125, [Ti8O8(OH)(4)(bdc-NH2)(6)] (bdc(2-) = 1,4-benzene dicarboxylate) is a highly porous metal-organic framework (MOF) that has a band gap lying within the ultraviolet region at about 2.6 eV. The band gap may be reduced by a suitable post-synthetic modification of the nanochannels using conventional organic chemistry methods. Here, it is shown that the photocatalytic activity of NH2-MIL-125 in the degradation of methylene blue under visible light is remarkably augmented by post-synthetic modification with acetylacetone followed by Cr-III complexation. The latter metal ion extends the absorption from the ultraviolet to the visible light region (band gap 2.21 eV). The photogenerated holes migrate from the MOF's valence band to the Cr-III valence band, promoting the separation of holes and electrons and increasing the recombination time. Moreover, it is shown that the MOF's photocatalytic activity is also much improved by doping with Ag nanoparticles, formed in situ by the reduction of Ag+ with the acetylacetonate pendant groups (the resulting MOF band gap is 2.09 eV). Presumably, the Ag nanoparticles are able to accept the MOF's photogenerated electrons, thus avoiding electron-hole recombination. Both, the Cr-and Ag-bearing materials are stable under photocatalytic conditions. These findings open new avenues for improving the photocatalytic activity of MOFs.
palavras-chave
METAL-ORGANIC FRAMEWORKS; VISIBLE-LIGHT PHOTOCATALYSIS; CARBON-DIOXIDE CAPTURE; METHYLENE-BLUE; DRUG-DELIVERY; TIO2; MOFS; SEMICONDUCTOR; OXIDATION; CATALYSIS
categoria
Chemistry
autores
Abdelhameed, RM; Simoes, MMQ; Silva, AMS; Rocha, J
nossos autores
João Rocha
Prof. Catedrático
Reda Mohamed Abdelhameed Ahmed
Bolseiro de pós-Doutoramentoagradecimentos
This work was developed in the scope of the projects CICECO-Aveiro Institute of Materials (Ref. FCT UID/CTM/50011/2013) and Organic Chemistry Research Unit (QOPNA; Ref. UID/QUI/00062/2013), financed by national funds through the FCT/MEC and when applicable co-financed by FEDER under the PT2020 Partnership Agreement. We also thank the Portuguese National NMR Network (RNRMN) and (RMA) FCT for the PhD research grant (SFRH/BD/51269/2010).