In 2005, Yaghi and co-workers developed new crystalline porous organic polymers known as covalent organic frameworks (COFs). These materials are built from covalent-bonding of organic building units consisting only of light elements and present remarkable characteristics such as low density, large surface area and a versatile combination of building units. During the last years, several advances have been made in the synthesis and development of new COFs. However, besides their potential of application in different areas like gas storage and development of new materials with optical and electrical properties, there are only few reports in the literature correlating the properties of COFs with practical applications. COF-300 is one of these interesting structures, which was described as the first time in 2009. It is a nanostructured material, with a crystalline arrangement and a high surface area (1400-1500 m2/g). Its synthesis is based on the condensation of the tetrakis-(4-aminobenzyl)carbon with terephtalaldehyde, yielding a basic structure containing imine functions. Aiming to take advantage of the outstanding properties of this material, we envisioned the development of a new heterogeneous catalyst for cross coupling reactions trough insertion of Pd(OAc)2 into COF-300 structure. Basically, Pd(OAc)2 was incorporated into the COF-300 pores by the impregnation technique. After fully characterization, its catalytic potential was explored in Heck, Suzuki and Sonogashira cross coupling reactions with more than sixty subtracts.  The reactions were carried out in mild conditions and moderated to excellent yields were obtained. In addition to the fact that it is a heterogeneous catalyst, which allows its reutilization and minimizes the amount of palladium in the products, the nanomeric ambient avoids palladium aggregation to form palladium black, which is inactive. Furthermore, the porous structure leads to a pre-organization of the reactants, what is beneficial for the reaction due to the probable decrease in the entropy of activation.

Cross-coupling reactions catalyzed by palladium caged into covalent organic framework nanopores

248th National Meeting (2014)

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