Construction of Novel Coordination Polymers Based on Pyrazole Carboxylic Acid and Doping for Enhancing the Photocatalytic Property Under Visible Light

Visible-light-driven photocatalysis is a promising approach for the degradation of organic pollutants due to its effective utilization of sunlight resources. Therefore, the design and synthesis of novel coordination polymers (CPs) as photocatalysts and the regulation of photocatalytic performance have attracted considerable attention. Herein, we designed and synthesized a light absorption ligand 1-(carboxymethyl)-1H-pyrazole-4-carboxylic acid (H₂cmpc) and prepared six novel CPs with different 3d transition metal ions, named [Mn₃(cmpc)₂(μ₃-OH)₂(H₂O)₄]·2H₂O (1), [M­(cmpc)­(H₂O)₃] (M = Co (2), Ni (3), Co_0.4Ni_0.6 (4)), and [M­(Hcmpc)₂(H₂O)₄] (M = Co (5), Ni (6)). The H₂cmpc organic linker has three kinds of coordination bridging modes in the six CPs. CP 1 presents a layered structure with a channel. CPs 2–4 are isostructural and show a one-dimensional chain structure. CPs 5 and 6 are isostructural and exhibit a mononuclear structure with six-coordinated metal ions, which are connected into a 3D supramolecular structure constructed through hydrogen bonds. Photocatalytic degradation experiments of CPs 2–4 were conducted, indicating that CPs 2–4 show excellent photocatalytic performance under visible light. Furthermore, Co/Ni codoping can enhance the photocatalytic performance compared with single metal CPs. The photocatalytic degradation mechanisms of CPs 2–4 have been investigated.