Pyridine-amide-based hetero-copper iodide for the photocatalytic degradation of dyes and aerosol discolouration of VOC gases

Abstract

Rare-earth-free copper iodide coordination polymers (CPs) are a versatile class of semiconductor light-emitting materials, which are of great interest for their narrow optical band gaps, long fluorescence lifetime and high photoluminescence quantum efficiency. In this article, we synthesized two new copper iodide CPs, namely [(CuI)(4-dpye)_0.5]_n (CP 1) and {[(Cu₄I₄)(3-bpah)₂]·3CHCl₃·MeCN}_n (CP 2), where 4-dpye = N,N′-bis(4-pyridinecarboxamide)-1,2-ethane and 3-bpah = N,N′-bis(3-pyridinecarboxamide)-1,2-cyclohexane, respectively, and the double-chain [CuI]_n ladder and [Cu₄I₄] tetramer nodes self-assembled with the ligands to form two kinds of two-dimensional (2D) frameworks. These two as-synthesized CPs were direct band gap semiconductors with optical band gaps of 2.68 eV and 2.45 eV, respectively, and the long fluorescence lifetime of CPs due to the slow carrier complexation caused by the triplet state luminescence of the CPs, which results in both fluorescence and good photocatalytic activity of the CPs and the photocatalytic degradation of Congo red (CR) can reach 98% within 240 min. Through the capture experiments, it was verified that the hole is the main active substance for the photocatalytic degradation of the CPs. This work reveals the feasibility of copper iodide clusters for wastewater purification. Due to the unique structure of the pyridine amide group, the gas chromism of CP 2 combined with volatile organic compound (VOC) gases occurs, which allows the hybrid cuprous iodide to be used for the rapid detection of VOC gases with low concentration by the naked eye. Combined with electrospinning technology, CPs were doped into polyacrylonitrile (PAN) to obtain a functionalized luminescent nanofiber composite membrane, which expanded the development of new fluorescent fabrics and new photochemical sensors.