In Situ Synthesis of Iron-Based Porphyrin Metal–Organic Frameworks for the Baeyer–Villiger Oxidation Using Air as an Oxidant

Iron-based porphyrin metal–organic frameworks (PMOFs) are a new type of material with good stability, catalytic activities, and reusability, which have broad application prospects. However, the synthesis of iron-based PMOFs with different metalloporphyrin units requires a considerable amount of reagents and time. Herein, an in situ synthesis method was developed to simplify the synthetic process of iron-based PMOFs. A series of highly stable iron-based PMOFs (M_situ-PMOF-3(Fe) (M = Fe, Co, Ni, Cu, Pd)) were synthesized in one pot without the preparation of metalloporphyrin ligands in advance. This synthesis method is simpler and more efficient, saving considerable time and material costs. The resultant M_situ-PMOF-3(Fe) exhibits a high tolerance to aqueous solutions with pH ranging from 0 to 11, as well as various organic solvents. The catalytic experiments show that both Fe_situ-PMOF-3(Fe) and Co_situ-PMOF-3(Fe) can catalyze the Baeyer–Villiger oxidation of cyclohexanone using air as an oxidant at 35 °C. Moreover, when the mixtures of Fe_situ-PMOF-3(Fe) and Co_situ-PMOF-3(Fe) were employed as catalyst, they can exert a cooperative catalysis effect, resulting in a significantly enhanced catalytic activity compared to a single component. The mild reaction condition, high catalytic efficiency, and excellent selectivity endow this catalytic system with a good application prospect. This work not only provides a new approach for the synthesis of iron-based PMOFs but also offers guidance for the Baeyer–Villiger oxidation reactions using air under mild conditions.