A one-stone-two-birds strategy for enhancing quantum yield and designing dual-emission AIE MOFs

Abstract

Enhancing the quantum yield of aggregation-induced emission (AIE) species (AIEgens) and revealing the emission mechanisms are challenging. Herein, we design and prepare metal-organic frameworks (MOFs) with an AIE ligand (2,3,5,6-tetrakis(4-carboxyphenyl) pyrazine) (TCPP) and Zr4+ metal cluster. The resulting Zr-TCPP exhibits enhanced blue emission, which is attributed to coordination-induced restriction of intramolecular rotation. Furthermore, Salicylalazine (SA) with AIE characteristic is encapsulated within the porous Zr-TCPP host. The restriction effect of channel transforms SA from colourless to bright yellow emission. Consequently, encapsulation-induced emission (EIE) is proposed as an additional evidence of AIE mechanism. The EIE strategy not only increases the quantum yield of SA@Zr-TCPP to 11.62% but also introduces a new fluorescence emission site within the AIE MOFs. To verify the EIE mechanism, high concentration of ClO- was selected as the target analytes, which disrupt the restriction effect of channel and unlock the molecule rotors of SA. The optical behaviors of the dual-emission SA@Zr-TCPP validates the proposed EIE mechanism and realized the ratiometric fluorescent detection of ClO-.