Excitation dependent multicolour luminescence and colour blue-shifted afterglow at room-temperature of europium incorporated hydrogen-bonded multicomponent frameworks

Fascinating multicoloured luminescence and long-lived afterglow have attracted tremendous interests due to their potential applications in display, information encryption, and organic electronics. Herein, room-temperature colour blue-shifted afterglow and excitation wavelength dependent multicoloured luminescence are developed based on an europium-doped hydrogen-bonded multicomponent framework built out of melamine and two aromatic carboxylic acids unit (MIT:Eu). The MIT:Eu material has been specially designed to yield multicolour luminescence including blue, green, and red emission. By altering the excitation wavelength from 254 to 365 nm, it displays colour tunable luminescence spanning from red to blue as a result of the independent activation of the three emission bands. The blue, red, and green emission characteristic lifetimes fall in distinctly different orders of magnitude of 10-9, 10-4, and 100 seconds respectively, which gives rise to a remarkable colour blue-shifted afterglow. Moreover the luminescence properties of these hydrogen-bonded frameworks can be further modulated by altering the water and europium content. On the basis of these unique multi-stimuli responsive emission properties, the application of MIT:Eu in multilevel information encryption is explored.