2D Cu(I)-I Coordination Polymer with Smart Optoelectronic Properties and Photocatalytic Activity as a Versatile Multifunctional Material.

This work presents two isostructural Cu(I)-I 2-fluoropyrazine (Fpyz) luminescent and semiconducting 2D coordination polymers (CPs). Hydrothermal synthesis allows the growth of P-1 space group single crystals, whereas solvent-free synthesis produces polycrystals. Via recrystallization in acetonitrile, P21 space group single crystals are obtained. Both show a reversible luminescent response to temperature and pressure. Structure determination by single-crystal X-ray diffraction at 200 and 100 K allows us to understand their response as a function of temperature. Applying hydrostatic/uniaxial pressure or grinding also generates significant variations in their emission. The high structural flexibility of the Cu(I)-I chain is significantly linked to the corresponding alterations in structure. Remarkably, pressure can increase the conductivity by up to 3 orders of magnitude. Variations in resistivity are consistent with changes in the band gap energy. The experimental results are in agreement with the DFT calculations. These properties may allow the use of these CPs as optical pressure or temperature sensors. In addition, their behavior as a heterogeneous photocatalyst of persistent organic dyes has also been investigated.