Optimization of the time and temperature of the microwave-assisted amination of phenylene-PMO


In this paper we report a study on the optimization of the amination of periodic mesoporous phenylene-silica (PMO) using microwave heating. The optimization was carried out for two key steps in the reaction, namely, (1) nitration of the bissilylated phenylene bridge, and (2) reduction of the nitro group to a primary amine. The temperatures of both reaction steps were varied between 37, 60, 75 and 90 degrees C. The reaction times studied were between 15 to 360 minutes. Microwave heating lead to significant reduction in the reaction times needed to achieve the maximum degree of nitration and amination compared to conventional means. After 15 minutes of reaction at 60 degrees C, a nitrogen density similar to that obtained for the same material synthesized conventionally was observed, and after 240 minutes of reaction time at 60 degrees C the nitrogen density was exceeded. A complete reduction of the nitro to the amine groups was observed after 15 minutes of reaction at 60 degrees C, which demonstrates the great potential of microwave irradiation in enhancing the kinetics of the post-synthesis functionalization of PMO materials, while preserving the molecular and mesoporous orders.



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Lourenco, MAO; Gomes, JRB; Ferreira, P

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This work was financed by FEDER funds through Programa Operacional Factores de Competitividade - COMPETE and by National Funds from FCT (Fundacao para a Ciencia e Tecnologia) in the framework of the CICECO project with reference FCOMP-01-0124-FEDER-037271 (Ref. FCT PEst-C/CTM/LA0011/2013) and FCOMP-01-0124-FEDER-015644 (PTDC/QUI-QUI/113678/2009) JRBG and PF thank FCT for Programa Investigador FCT and MAOL thanks FCT for the PhD. grant with ref. SFRH/BD/80883/2011. The authors thank the National Network of electron microscopy and University of Aveiro Project REDE/1509/RME/2005. The authors acknowledge also Alichandra Castro for the support in the SEM analyses.

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