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Previous issue date: 2014-01-24 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / As redes metalorg?nicas (MOFs) s?o h?bridos, normalmente cristalinos, constitu?dos de subunidades inorg?nicas, metais ou clusters met?licos, conectados por ligantes org?nicos polit?picos de forma repetitiva originando estruturas em duas ou tr?s dimens?es, geralmente porosas. Neste trabalho foram sintetizadas MOFs com ?ons lantan?deos (La3+ e Gd3+) e ligantes tipo dicarboxilatos (?cidos isoft?lico e o tereft?lico) pelos m?todos hidrot?rmico, solvot?rmico e hidro(solvo)t?rmico. Os efeitos da rota sint?tica sobre a estrutura e propriedades das MOFs foram estudados, bem como do tipo de aquecimento, convencional ou por microondas. As amostras obtidas na forma de p?s foram caracterizadas por difra??o de raios-X, espectroscopia de infravermelho, analises t?rmicas e microscopia eletr?nica de varredura. Os resultados sugerem a necessidade de uma base, org?nica ou inorg?nica, para promover a desprotona??o do ligante, uma vez que nas amostras preparadas pelo m?todo hidrot?rmico, sem o aux?lio de uma base, n?o houve forma??o de uma rede metalorg?nica. Por outro lado, a presen?a de DMF, como solvente ou co-solvente, proporcionou a desprotona??o do ligante com consequente forma??o das MOFs. Pelo menos duas estruturas cristalinas diferentes foram identificadas para as amostras preparadas com ?cido tereft?lico. Estas amostras apresentam isoestruturas semelhantes ?s reportadas para as fases Eu(1,4-BDC)DMF e Tb(1,4-BDC)H2O. A presen?a de ?gua no meio reacional, m?todo hidro(solvo)t?rmico, direcionou o crescimento da estrutura de maneira diferente da observada quando em sua aus?ncia. Isto pode ser justificado pela diferen?a na forma de coordena??o dos ?ons lantan?deos por ?gua e por DMF. Apesar de n?o terem sido identificadas por DRX, as amostras preparadas com ?cido isoft?lico tamb?m apresentam estruturas metalorg?nicas, confirmadas pelo deslocamento da banda referente ao estiramento do grupo carbonila em rela??o a ligante puro, nos espectros de infravermelho. Este deslocamento tamb?m foi observado nas amostras preparadas com ?cido tereft?lico. As analises de microscopia eletr?nica de varredura sugerem que a morfologia dos p?s e significativamente dependente do tipo de aquecimento usado, convencional ou micro-ondas. / Metal Organic Frameworks (MOFs) are hybrids materials, often crystalline,
consisting of metal or metal clusters, connected by polytopic organic ligands
repetitively, leading to structures, usually porous. In this work, MOFs based on
lanthanide ions (La3+ and Gd3+) and dicarboxylate type of ligands (isophthalic and
terephthalic acids), were synthesized by hydrothermal, solvothermal and
hydro(solvo)thermal methods. The effects of the synthetic route as well as the type of
heating, conventional or by microwave, on the structure and properties of MOFs were
studied. The powder samples obtained were characterized by X-ray diffraction,
infrared spectroscopy, thermal analysis and scanning electron microscopy. The
results suggest that the addition of an organic or inorganic base is needed to
promote the deprotonation of the ligand, since in the samples prepared by the
hydrothermal method, without the use of a base, no formation of the metalorganic
framework was observed. On the other hand, the presence of DMF as solvent or cosolvent,
afforded the deprotonation of the ligand with the consequent formation of
MOFs. At least two different crystalline structures were identified for the samples
prepared with terephthalic acid. These samples are isostructural with those reported
for phases Eu(1,3-BDC)DMF, Eu2(1,4-BDC)3 (DMF)2 and Tb(1,4-BDC)H2O. The
presence of water in the reaction medium in the hydro(solvo)thermal method,
provoked the growth of the structure different from that observed in the absence of
water. This can be explained by the difference in the coordination mode of water and
DMF to lanthanide ions. Although not identified by XRD, the samples prepared with
isophthalic acid, also present metalorganic structures, which was confirmed by the
presence of the characteristic displacement of the carbonyl group band in their
infrared spectra, compared to the spectrum of the pure ligand. This shift was also
observed in the samples prepared with terephthalic acid. Thermal analisys shows
that the metal organic frameworks do not collapse occurs at a temperature below
430?C.The analysis of scanning electron microscopy suggests that the morphology of
powders is highly dependent on the type of heating used, conventional or by
microwave.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/20710 |
| Date | 24 January 2014 |
| Creators | Leite, Ana Karina Pereira |
| Contributors | 00735018405, http://lattes.cnpq.br/8938691250105531, Bicudo, Tatiana de Campos, 25935096862, http://lattes.cnpq.br/2712586287719863, Kulesza, Joanna Elzbieta, 70134641477, http://lattes.cnpq.br/1568423340359601, Neves, Jorge Luiz, 94131759691, http://lattes.cnpq.br/4215225925783359, Alves J?nior, Severino, Barros, Br?ulio Silva |
| Publisher | Universidade Federal do Rio Grande do Norte, PROGRAMA DE P?S-GRADUA??O EM QU?MICA, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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