A Non-Centrosymmetric Dual-Emissive Metal–Organic Framework with Distinct Nonlinear Optical and Tunable Photoluminescence Properties

A novel dual-emissive metal–organic framework [Pb3(BPT)2(phen)2]·phen (1) has been obtained by hydrothermal reactions of biphenyl-3,4′,5-tricarboxylic acid (H3BPT), phen, and lead nitrate in aqueous solution. It consists of a main right-handed helix and three left-handed helical chains with the three left-handed helical chains sharing the same helical axis and further enwinding the main right-handed helical chain alternately. The BPT3– ligands join the 1D helical chains into 2D layers with the terminal phen liands extending upward and downward, which are further interdigitated into a 3D packing supramolecular architecture through π–π interactions between the phen molecules of neighbor layers. The second harmonic generation (SHG) measurement reveals that 1 is nonlinear optical active with SHG efficiency approximately equivalent to that of the standard potassium dihydrogen phosphate (KDP), and photoluminescent investigation displays that complex 1 exhibits distinct tunable yellow-to-violet photoluminescence by varying the excitation light.