Porphyrins are selected as building units to synthesize porphyrin‐based covalent organic polymers (COPs), which can combine the excellent properties of covalent organic polymers with the fantastic catalytic effect of porphyrin to obtain a heterogeneous catalyst with excellent catalytic activity. In this work, the novel benzimidazole‐linked porphyrin COPs MPp‐BTA (M = 2H, Zn, Co) were synthesized using a new porphyrin with aldehyde group peripherally MPp (M = 2H, Zn, Co) and 1,2,4,5‐tetraminobenzene tetrahydrochloride (BTA) as monomers. The synthesized MPp‐BTA were carefully characterized by FT‐IR, UV–vis, SEM, TEM, TG, and PXRD. As heterogeneous catalyst, MPp‐BTA (M = Zn, Co) shows the high catalytic activity and stability for cycloaddition of CO2 with phenyl glycidyl ether (PGE) under mild conditions (80°C, 0.1 MPa CO2), and the yield of cyclocarbonate can reach 95% and 92% respectively. In addition, the recycling stability of ZnPp‐BTA was investigated, and the yield of cyclocarbonate was still remained at 86% after five cycles. Furthermore, MPp‐BTA (M = 2H, Zn, Co) can be used directly as heterogeneous photocatalysts for selective oxidation of thioanisole to methyl phenyl sulfoxide. To our delight, H2Pp‐BTA shows satisfactory photocatalytic performance, and the yield of methyl phenyl sulfoxide can reach 93% in 4 h.
Two porphyrins, named H2TEtImP and H2DEtImP, with the four and two N‐ethylated imidazole groups, respectively, as well as their metalloporphyrins, M‐TEtImP (M = Zn, Mn, Co, Mg) and Zn‐DEtImP, were synthesized and characterized by ultraviolet–visible (UV–Vis), mass spectrometry (MS), proton nuclear magnetic resonance (1H NMR), and Fourier transform infrared (FTIR) successfully. The catalytic activity of these newly synthesized porphyrins with metal centers and halogen ions as variables on the cycloaddition reaction between carbon dioxide (CO2) and epoxides was investigated under solvent‐free conditions. The experimental results strongly verified that both halogen ions and metal centers were indispensable active sites. The metal catalytic activity increased in the order Co < Mn < Mg < Zn. The turnover frequency (TOF) of Zn‐TEtImP for the cycloaddition reaction of CO2 and epichlorohydrin was as high as 2213 h−1 (120°C, 1 MPa CO2, 6 h). Moreover, the wide applicability of Zn‐TEtImP to this reaction was demonstrated by substrate extension experiments, and the excellent recyclability of Zn‐TEtImP was confirmed. Finally, the synergistic catalytic mechanism of Lewis acid (metal center) and nucleophile (Br−) was proposed based on the catalytic results.
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