Síntese e funcionalização de Metal-Organic Frameworks (MOFs) visando aplicação como catalisadores heterogêneos em reações de conversão de CO2
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Data
2017-05-03
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Universidade Estadual Paulista (Unesp)
Resumo
Neste projeto foram sintetizados e caracterizados materiais porosos conhecidos como Metal-Organic Frameworks (MOFs) que abrangem uma área da química que tem experimentado um crescimento muito grande nas duas últimas décadas. MOFs são compostos cristalinos contendo espaços potencialmente vazios (poros) construídos a partir de íons ou clusters metálicos interconectados por espaçadores orgânicos. Além da diversidade estrutural e topológica, estes materiais têm enorme potencial para muitas aplicações. Dentro desse contexto, o objetivo central do trabalho foi a preparação de MOFs de cobre(II) e zinco(II) e investigação da potencialidade de aplicação em catálise heterogênea. Dentre outros materiais, a MOF MOF-INZ foi preparada pela primeira vez a partir da funcionalização da HKUST-1 via processo PSM (Pos-Synthetic Modification) pela coordenação da isoniazida nos centros coordenativamente insaturados (CUSs) do íon cobre(II) do material precursor ativado. A utilização desse material como catalisador em reações de cicloadição de CO2 frente ao epóxido de propileno resultou em 95% de conversão do reagente em carbonato de propileno (após 72 horas, em presença de TBAI). A última etapa do trabalho consistiu na preparação das MOFs ZIF-8 e HKUST-1 em escala nanométrica, usando moduladores de concentração, e no desenvolvimento de uma técnica muito elegante para a formação de filmes finos sobre nanotubos de dióxido de titânio (com diâmetros da ordem de 50-100 nm). Os materiais híbridos preparados foram então submetidos a reações foto- e fotoeletrocatalíticas de redução de CO2. As MOFs adsorvidas nos eletrodos nanoestruturados mostraram atividades significativamente mais altas em comparação com o eletrodo não modificado. Sob irradiação de luz e na presença de ácido ascórbico, o compósito Ti/TiO2-ZIF-8 gerou cerca de 30 mmol/L de etanol e 2 mmol/L de metanol em fase gasosa, enquanto que reações fotoeletrocatalíticas de redução de CO2 produziram 104 mmol/L e 17 mmol/L desses mesmos produtos, respectivamente. Do que seja do nosso conhecimento, essa é a primeira vez que a redução fotoeletrocatalítica desse importante gás causador do efeito estufa é realizada sobre materiais baseado em MOFs e abre uma frente de pesquisa bastante promissora no que tange a introdução dessa importante classe de materiais porosos no design de fotoeletrocatalisadores para reações gasosas.
In this project, porous materials known as Metal-Organic Frameworks (MOFs) were synthesized and characterized, which cover a chemistry area that has experienced a very large growth in the last two decades. MOFs are crystalline compounds containing potentially empty spaces (pores) constructed from ions or metal clusters interconnected by organic spacers. In addition to structural and topological diversity, these materials have enormous potential for many applications. In this context, the main objective of the work was the preparation of copper (II) and zinc (II) MOFs and the investigation of the potentiality of application in heterogeneous catalysis. Among other materials, MOF MOF-INZ was prepared for the first time from the functionalization of HKUST-1 via PSM (Post-Synthetic Modification) process by the coordination of isoniazid to the coordinated unsaturated (CUSs) centers of the copper (II) activated precursor. The use of this material as a catalyst in CO2-cycloaddition reactions to propylene epoxide resulted in 95% conversion of the reactant into propylene carbonate (after 72 hours in the presence of TBAI). The last stage of the work consisted in the preparation of the ZIF-8 and HKUST-1 MOFs at nanoscale using concentration modulators and the development of a very elegant technique for the formation of thin films on titanium dioxide nanotubes (with diameters in the order of 50-100 nm). The prepared hybrid materials were then submitted to photo- and photoelectrocatalytic CO2 reduction reactions. The MOFs adsorbed on the nanostructured electrodes showed significantly higher activities compared to the unmodified electrode. Under light irradiation and in the presence of ascorbic acid, the Ti / TiO2-ZIF-8 composite generated about 30 mmol / L of ethanol and 2 mmol / L of methanol in the gas phase, while photoelectrocatalytic CO2 reduction reactions produced 104 Mmol / L and 17 mmol / L of these same products, respectively. To our knowledge, this is the first time that the photoelectrocatalytic reduction of this important greenhouse gas is carried out on materials based on MOFs and opens a very promising research front regarding the introduction of this important class of porous materials in the design of photoelectrocatalysts for gaseous reactions.
In this project, porous materials known as Metal-Organic Frameworks (MOFs) were synthesized and characterized, which cover a chemistry area that has experienced a very large growth in the last two decades. MOFs are crystalline compounds containing potentially empty spaces (pores) constructed from ions or metal clusters interconnected by organic spacers. In addition to structural and topological diversity, these materials have enormous potential for many applications. In this context, the main objective of the work was the preparation of copper (II) and zinc (II) MOFs and the investigation of the potentiality of application in heterogeneous catalysis. Among other materials, MOF MOF-INZ was prepared for the first time from the functionalization of HKUST-1 via PSM (Post-Synthetic Modification) process by the coordination of isoniazid to the coordinated unsaturated (CUSs) centers of the copper (II) activated precursor. The use of this material as a catalyst in CO2-cycloaddition reactions to propylene epoxide resulted in 95% conversion of the reactant into propylene carbonate (after 72 hours in the presence of TBAI). The last stage of the work consisted in the preparation of the ZIF-8 and HKUST-1 MOFs at nanoscale using concentration modulators and the development of a very elegant technique for the formation of thin films on titanium dioxide nanotubes (with diameters in the order of 50-100 nm). The prepared hybrid materials were then submitted to photo- and photoelectrocatalytic CO2 reduction reactions. The MOFs adsorbed on the nanostructured electrodes showed significantly higher activities compared to the unmodified electrode. Under light irradiation and in the presence of ascorbic acid, the Ti / TiO2-ZIF-8 composite generated about 30 mmol / L of ethanol and 2 mmol / L of methanol in the gas phase, while photoelectrocatalytic CO2 reduction reactions produced 104 Mmol / L and 17 mmol / L of these same products, respectively. To our knowledge, this is the first time that the photoelectrocatalytic reduction of this important greenhouse gas is carried out on materials based on MOFs and opens a very promising research front regarding the introduction of this important class of porous materials in the design of photoelectrocatalysts for gaseous reactions.
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Palavras-chave
Metal-Organic Frameworks (MOFs), Catálise heterogênea, Cicloadição de CO2, Fotocatálise, Fotoeletrocatálise de redução de CO2