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

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_<i>x</i>)_0.5]·guests}_<i>n</i>, 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.