Synthesis, characterization, and study of emission properties of discrete (0D) and extended (nD) copper(I) iodide hybrid materials (CuxIyLn)

Inorganic-organic hybrid semiconductors represent an important class of functional materials. This class of materials is both fundamentally and technologically important because of its very rich structural chemistry and its interesting, sometimes unique, properties. The integration of both inorganic and organic modules in a single crystal lattice enables the combination of the features of inorganic compounds (electronic, magnetic, optical, thermal, and mechanical properties) with those of organic molecules (structural flexibility, processability, lightweight, and functionalizability) in the resulting hybrid structures, with greatly enhanced and improved structural, chemical, and physical properties. Among them, a new hybrid material family has been recently developed: these compounds consist of covalently bonded anionic copper(I) halide (CuX, where X = F, Cl, Br, I) inorganic modules that form coordinative and ionic bonds with cationic organic ligands, designated as All-In-One (AIO) structures. Being low toxic, based on earth abundant elements, highly stable, easily processable and possessing excellent internal quantum yields (IQYs), AIO hybrid materials represent a promising class of environmental-friendly materials, overcoming many of the issues of the other inorganic-organic hybrid semiconductors. In the present work, a variety of new CuI-based hybrid materials has been synthesised and characterised, and their functional properties have been studied. Pyridine, caffeine, DABCO, and HMTA have been chosen as ligands in order to obtain at least one compound for each of the three classes of CuI hybrid materials. Functionalisation of those molecules via alkylation reaction have led to the target ligands needed for the preparation of the relative CuI-based hybrid compounds. Structural information about CuI hybrid species have been determined by XRD measurements. A variety of structural spatial groups, along with two different Cu atoms coordination geometry (distorted planar trigonal and most diffuse distorted tetrahedral) and crystal packing (given by ionic pairs, 0D clusters, and 1D linear polymeric chains), underlines how vast and peculiar this class of hybrid materials is. Depending on the choice of ligands and reaction conditions, other interactions can further stabilise CuI hybrid compound structures, ranging from π-stacking of aromatic rings to ordered disposition of inorganic modules around cationic centres of aggregation through electrostatic interactions. The preliminary luminescence properties of the obtained CuI-based hybrid materials were explored. 1D-Cu2I3(Bz-HMTA) (MM4) has been then chosen as the model catalyst for photoremediation applications. Rhodamine B (RhB) and Methylene Blue (MB) have been chosen as organic pollutants models. MM4 was activated using a 375 nm LED close to its maximum absorption peak; UV-Vis spectra were registered over time intervals in order to monitor the photodegradation of the organic dyes. Data collected on MB shows an almost total dye adsorption on MM4 powder, while data obtained on RhB denote an excellent photodegradation activity of the AIO compound. At the end of the experiments, the residual concentration of both MB and RhB was less than 10% of its initial value. The interest towards multifunctional materials has continuously increased over the last few years. Materials capable of pollutant adsorption and degradation at the same time are highly desirable for environmental remediation strategies and these new AIO CuxIyLn materials proved to be ideal candidates.