Bifunctional Porphyrin-Based Nano-Metal–Organic Frameworks: Catalytic and Chemosensing Studies

Abstract

The use of 5,10,15,20-tetrakis(p-phenylphosphonic acid)porphyrin (H10TPPA) as a linker in the preparation of porphyrin-based metal–organic frameworks (Por-MOFs) through coordination to lanthanides cations is reported. The resulting unprecedented materials, formulated as [M(H9TPPA)(H2O)x]Cl2·yH2O [x + y = 7; M3+ = La3+ (1), Yb3+ (2), and Y3+ (3)], prepared using hydrothermal synthesis, were extensively characterized in the solid-state, for both their structure and thermal robustness, using a myriad of solid-state advanced techniques. Materials were evaluated as heterogeneous catalysts in the oxidation of thioanisole by H2O2 and as chemosensors for detection of nitroaromatic compounds (NACs). Nano-Por-MOFs 1–3 proved to be effective as heterogeneous catalysts in the sulfoxidation of thioanisole, with Por-MOF 1 exhibiting the best catalytic performance with a conversion of thioanisole of 89% in the first cycle and with a high selectivity for the sulfoxide derivative (90%). The catalyst maintained its activity roughly constant in three consecutive runs. Por-MOFs 1–3 can be employed as chemosensors because of a measured fluorescence quenching up to 70% for nitrobenzene, 1,4-dinitrobenzene, 4-nitrophenol, and phenol, with 2,4,6-trinitrophenol exhibiting a peculiar fluorescence profile.