Room temperature synthesis of a luminescent crystalline Cu-BTC coordination polymer and metal-organic framework

Synthesis of crystalline materials is elemental in the field of coordination chemistry towards optical applications. In the present work, coordination between copper and benzene-1,3,5-tricarboxylic acid (BTC) is controlled by adjusting the pH scale of the reaction mixture at room temperature to synthesize two crystalline structures: metal-organic framework HKUST-1 and coordination polymer Cu(BTC)·3H₂O. The post-synthesis transformation of HKUST-1 into Cu(BTC)·3H₂O is further demonstrated. Single crystals of both structures are studied by multi-laser Raman and luminescence spectroscopy. It is found that both crystals exhibit photoluminescence in the range of 700-900 cm^-1 within the optical gap of the bulk materials, which can be associated with crystallographic defects. This work gives impetus for the synthesis of large metal-organic crystals based on which optical properties can be studied in depth.