Functionalization of Cu3BTC2@IL composites with Pd(II) for catalytic applications

Abstract

Metal-organic frameworks could be excellent supports for active catalytic species in order to obtain heterogeneous and reusable catalysts, easily removable from the reaction media.[1,2] Additionally, the presence of unsaturated metal centres in their pores provides a superb opportunity to tackle with reactions that requires more than one type of metal centre.[3] In order to obtain heterometallic catalyst we have immobilized Pd(II) into the pores of the well studied Cu3BTC2 MOF (BTC= benzene-1,3,5-tricarboxilate) with the help of imidazolium derivated ionic liquids (IL). The preparation of the catalyst was made in two steps. Firstly, the Cu3BTC2 was charged with [BMIM][BF4] and [BMIM][PF6] ionic liquids(BMIM= 1-Butyl-3-methylimidazolium). The stability of the composite materials, both chemical and thermal, was studied. Then, the insertion of palladium was made in basic media. By means of EDX the presence of Pd into the structural pores was proved and the quantification was made by ICP-AES. The powder DRX of the Cu3BTC2@[BMIM][Cation]-Pd samples show no structural changes with respect to the pristine Cu3BTC2. The functionalized material was tested as heterogeneous catalyst for Suzuki-Miyaura coupling reactions. The reactions were made in methanol at 70 ºC and using K2CO3 as base. The Pd:substrate molar ratio was set at 0.1 %. The activity was firstly studied using 4-bromotoluene and phenylboronic acid as reagents. The total conversion of the reaction reached 91 % in 1.5 hours with a selectivity towards the cross-coupling product of 67 %. Afterwards, other substrates were tested to study the scope of the reaction. When using 4-bromoanisole and phenylboronic acid, 67% of conversion was reached after 4 hours with a 100 % of selectivity towards the cross-coupling product. References: [1] P. Valvekens, F. Vermoortele and D. D. Vos, Catal. Sci. Technol., 2013, 3, 1435–1445. [2] E. S. Larrea, R. Fernández de Luis, J. Orive, M. Iglesias and M. I. Arriortua, Eur. J. Inorg. Chem., 2015, 2015, 4699–4707. [3] D. Saha, R. Sen, T. Maity and S. Koner, Langmuir, 2013, 29, 3140–3151.