The polyoxometalates anchored onto three-dimensional carbon foam for efficient removal of water pollutants

Polyoxometalates are regarded as electron sponges in catalytic processes due to the capability of accommodating and releasing multiple electrons. However, the aggregation and high solubility in water pose challenges in reuse during the photocatalytic degradation of organic pollutants. Herein, we designed a large-scale preparable carbon foam support with three-dimensional porous structure and used the sol-gel method to tightly anchor cobalt-substituted Keggin-type polyoxometalates onto it. The composite (CoSiW11O39-CF-X) was characterized using SEM, FT-IR, Raman, XPS, etc. CoSiW11O39-CF-0.2 exhibits excellent photocatalytic degradation ability towards the MB with a rate constant of 8.62 × 10-3 min−1. The addition of carbon foam enhanced the separation and migration rate of photo-induced charges, thereby improving the photocatalytic efficiency. Additionally, the composite demonstrated excellent stability and reusability in four cyclic experiments. Meanwhile, The free radical capture experiments reveal that h+ and O2– were identified as the main active species contributors. Based on the energy band theory, a reasonable Z-scheme heterojunction mechanism has been proposed to explain the process of photocatalytic degradation.