The synergistic effects involving surface adsorption and photocatalytic degradation commonly play significant roles in the removal of persistent synthetic organics from wastewater in the case of porous semiconductors. Inspired by the visible-light harvesting advantages of porphyrin-based MOFs, a capsule-like bimetallic porphyrin-based MOF (PCN-222(Ni/Hf)) has been successfully constructed through a facile hydrothermal method. In which, the Hf (IV) ions were exactly bonded to the carboxyl groups substituted on the porphyrin rings, meanwhile the Ni (II) ions were finely bonded to the −N inside the porphyrin rings. The adsorption/photocatalytic performances were assessed by using four persistent dyes including rhodamine B (RhB), basic violet 14 (BV14), crystal violet, and acid black 210 (AB210) as the target substances, and enhanced total removal efficiency was obtained by the bimetallic PCN-222(Ni/Hf) in comparison with that of single PCN-222(Hf). The electrochemical analyses and the sacrificial agent capture experiments were carried out to elucidate the photocatalytic mechanism, and the adsorption/photocatalytic stability of PCN-222(Ni/Hf) is also investigated. The work has broadened the applications of porphyrin-based MOFs in the removal of organics by combining their excellent surface adsorption capacity and photocatalytic activities.
Desen Zhou,Xuan Zhang,Zheng Li,Jun Zhang,Tielin Wang,Shaowen Cao
Photocatalytic conversion of CO 2 to usable fuels provides a new strategy for solving energy problems and the greenhouse effect. Porphyrin-based metal-organic frameworks (MOFs) are promising in photocatalysis due to their remarkable light harvesting ability, and the metal active site and its coordination environment can be further adjusted to achieve the high activity. In this work, g-C 3 N 4 /PCN-222 composites with different porphyrin metal centers were fabricated and the g-C 3 N 4 /PCN-222(Fe III ) catalyst showed the highest photocatalytic CO 2 reduction performance than that of g-C 3 N 4 /PCN-222(Fe II ) and other g-C 3 N 4 /PCN-222( M , M = Co, Ni, Cu, Zn) composites. Experimental studies and theoretical calculations showed that the axial coordination in g-C 3 N 4 /PCN-222(Fe III ) distorts the square planar field (Fe-N4) to quasi-octahedral coordination, which led to the moderate adsorption ability of CO 2 reduction intermediate (*CO), resulting in the high photocatalytic activity.
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