Highly thermally stable heterogeneous catalysts: study of 0D and 3D porphyrinic MOFs

Abstract

Heterogeneous catalysts are a great bet for green chemistry in many industrial processes and, in the past decade, promising results have been achieved in order to improve the catalytic activity of Metal Organic Frameworks (MOFs). Accordingly, porphyrins make possible to design new coordination polymers with better properties, taking into account the important functions they develop in nature. In this sense, porphyrin-based MOFs are becoming very relevant in heterogeneous catalysis. Thus, the aim of this work was obtaining metalloporphyrinic MOFs exhibiting catalytic activity. Studying the effect of dimensionality on the MOF properties (including thermal stability and catalytic activity), in this work we study two catalysts with different dimensionalities, 3D [Ni5(H2TCPP)2O(H2O)4]•nS (1) and 0D [Cu(H4TCPP)]•6DMF (2) (where H6TCPP is meso-tetra(4-carboxyphenyl)porphyrin, DMF is N,N-dimethylformamide and S is the solvent). The structural features of both compounds, combined with their high thermal stability and accessible networks, are responsible for the excellent behaviour as heterogeneous catalysts. It is worth mentioning that significant reduction in reaction time compared to other reported catalysts has been observed. The recyclability of one of the herein studied porphyrin-based MOFs is outstanding. Further structural and thermal characterization has been carried out by means of single crystal X-ray diffraction, IR spectroscopy, thermogravimetry (TG), powder X-ray diffraction (XRD) and transmission electron microscopy (TEM).