Porphyrin-based metal-organic frameworks loaded with Ag nanoparticles and their nanofibrous filters for the photocatalytic reduction of Cr(VI)

Irresponsible discharge of industrial wastewater containing hexavalent chromium (Cr(VI)) is a serious envi-ronmental problem and poses a great threat to human health. In this work, the 4,4,4,4-(porphyrin-5,10,15,20-tetrayl) tetrakis (benzoic acid) (TCPP) ligand was introduced into UiO-66-NH2 through one-pot synthesis to form Zr-TCPP. The introduction of TCPP expands the visible light absorption range of the material, which is of great significance for photocatalysts. To further improve the photocatalytic performance, subsequently, Zr-TCPP with different loading of Ag NPs (AZTx, x = 1,3,5,10) were prepared by in situ reaction under UV light. Compared with bare Zr-TCPP, the prepared AZTx exhibited enhanced photocatalytic activity for the Cr(VI) photoreduction reaction. Among the hybrid photocatalysts, Ag NPs:Zr-TCPP at 5 % mass ratio (AZT5) prompted 94.1 % Cr(VI) reduction within 30 min in a solution with Cr(VI) concentration of 10 mg/L. In addition, the nanofibrous filters of catalyst and polyacrylonitrile (PAN) were fabricated using Electrospinning technology, performing significant photocatalytic reduction of Cr(VI) in the circulation system with easy recovery. This work provides insights into photocatalyst reconstruction strategies while broadening the application of traditional powder photocatalysts in photocatalysis, which paves the way for the design of efficient photocatalysts for environmental applications.