Nanoconfinement of Tetraphenylethylene in Zeolitic Metal-Organic Framework for Turn-on Mechanofluorochromic Stress Sensing

TL;DR

This study develops a novel AIE@MOF composite with nanoconfinement that exhibits turn-on mechanofluorochromism, significantly enhancing sensitivity and enabling stress history recording for advanced sensing and optoelectronic applications.

Contribution

It introduces the first Guest@MOF system combining AIE and MOF, demonstrating enhanced mechanofluorochromism and stress sensing capabilities through nanoconfinement effects.

Findings

Nanoconfinement boosts TPE sensitivity tenfold.

The composite exhibits permanent fluorescence after stress release.

It can record stress history due to prevention of recrystallization.

Abstract

Mechanofluorochromic materials are of great significance for the fabrication of innovative sensors and optoelectronics. However, efficient mechanofluorochromic materials are rarely explored due to the deficiency of existing design strategies. Here, we demonstrate the incarceration of aggregation-induced emission (AIE) materials within metal-organic framework (MOF) single crystals to construct a composite system with turn-on mechanofluorochromism. A new type of AIE@MOF material was designed: integrating a zeolitic MOF (ZIF-71) and tetraphenylethylene (TPE, a topical AIE material) to generate a TPE@ZIF-71 system with exceptional turn-on type mechanofluorochromism. Using terahertz vibrational spectroscopy, we show the unique fluorochromism emanates from the enhanced nanoconfinement effect exerted by ZIF-71 host on TPE guest under pressure and its permanent fluorescence after stress release. Compared with pure TPE, we demonstrate the nanoconfinement in AIE@MOF not only changes the TPE's turn-off type sensing behavior to a turn-on type, but boosts the original sensitivity markedly by tenfold. Significantly, because ZIF-71 prevents the spontaneous recrystallization of TPE upon unloading, this allows TPE@ZIF-71 to record the stress history. This is the first demonstration of the Guest@MOF system combining the concepts of AIE and MOF; its promising properties and potential engineering applications will stimulate new directions pertaining to luminescent stress sensors and smart optics.