Mechanochromic Luminescence Behavior in Multivariate Metal–Organic Frameworks Based on Linker Effects

Abstract

Mechanochromic luminescence molecules show great appeal in the realm of intelligent luminescent materials but face great challenges from aggregation-caused quenching and/or amorphization during mechanical processing. Integrating aggregation-induced emission (AIE) luminogens into the architecture of highly crystalline metal–organic frameworks (MOFs) could potentially address these issues. In this work, two isomorphic Zn-MOFs ({[Zn(TCPE)_0.5(L_x)_0.5]·guests}_n, where H₄TCPE = 1,1,2,2-tetra(4-carboxylphenyl)ethylene, L₁ = triethylenediamine, and L₂ = piperazine) are synthesized via a multiligand assembly approach. The mechanochromic luminescence behaviors observed in these Zn-MOFs have been thoroughly analyzed, with a focus on the influence of linker effects. Under mechanical grinding, the lattice contraction of Zn-MOFs is accompanied by the distortion of the benzene rings within TCPE^4–, leading to altered intramolecular twisted charge transfer within the Zn-MOFs, which subsequently changes their luminescence properties. The potential application of this luminescence behavior in light-emitting diodes was preliminarily explored.