Dynamic Full‐Color Tuning of Organic Chromophore in a Multi‐Stimuli‐Responsive 2D Flexible MOF

Abstract

Developing universal stimuli‐responsive materials capable of emitting a broad spectrum of colors is highly desirable. Herein, we deliberately grafted a conformation‐adaptable organic chromophore into the established coordination space of a flexible metal–organic framework (MOF). In terms of the coupled structural transformations and the space confinement, the chromophore in the MOF matrix underwent well‐regulated conformational changes under physical and chemical stimuli, simultaneously displaying thermo‐, piezo‐, and solvato‐fluoro‐chromism with color tunability over the visible range. Owing to the resilient nature and the reduced dimensionality of the selected coordination space, all three color modulations behaved in a sensitive and self‐reversible manner, each following a linear correlation of the emission maximum with stimulus. Single‐crystal X‐ray diffraction of the variable‐temperature structures and solvent‐inclusion crystals elucidated the intricate color varying mechanisms.

Smart Tetraphenylethene‐Based Luminescent Metal–Organic Frameworks with Amide‐Assisted Thermofluorochromics and Piezofluorochromics

“…The absolute sensitivity of DEF ∈ ZnETTB (29.98 nm GPa −1 ) at low pressure is much higher than that of 2D perovskite materials (14.4 nm GPa −1 ), showing great potential as an ultrasensitive pressure sensor. [ 36 ] ZnETTB showed linear correlations between emission peaks and hydrostatic pressure at all tested ranges (Figure 5g). Such a linear correlation could also be observed for DEF ∈ ZnETTB with a similar slope when the pressure is above 3 GPa, indicating their similar piezofluorochromic behavior at high pressures, while DEF ∈ ZnETTB is much more sensitive to pressure change at low‐pressure range (below 3 GPa).…”

“…The piezofluorochromic behavior of DEF ∈ ZnETTB was investigated in the hydrostatic pressure experiment with a diamond anvil cell (DAC) device (Figure 5a). [35,36] With the pressure increasing from 1 atm (101 kPa) to 10.63 GPa, the crystals changed from bright blue fluorescence to dim yellowish emission under 365 nm light (Figure 5a). Solid-state emission spectra of DEF ∈ ZnETTB further confirmed the redshifted emission peaks from 463 to 586 nm along with gradually decreased brightness, upon increasing the hydrostatic pressure (Figure 5b; Figure S18a, Supporting Information).…”

“…[31] Therefore, AIEgens with twisted molecular geometry and molecular rotors shall be superb candidates to design novel luminescent MOFs with smart responsiveness. [22,23,[32][33][34][35][36] Herein, we report an amide-responsive luminescent AIE MOF (ZnETTB) built with elongated AIE ligand, and demonstrate that the incorporation of amide in framework could afford the MOF with excellent thermofluorochromic behavior and largely improved piezofluorochromic sensitivity. In specific, elongation of TPE-derived ligand from 4,4′,4″,4‴-…”

“…[ 35 ] Bu and co‐workers also reported a thermofluorochromic MOF (NKU‐128) by using tri(4‐(pyridine‐3‐yl)phenyl)amine (3‐TPPA), capable of conformational change as the ligand. [ 36 ] Recently, we also demonstrated that MOF with differently charged SBUs could be obtained with twisted AIE ligand, which exhibited specific HCl‐vapor‐induced fluorescence and magnetism switch. [ 31 ] Therefore, AIEgens with twisted molecular geometry and molecular rotors shall be superb candidates to design novel luminescent MOFs with smart responsiveness.…”

“…[ 31 ] Therefore, AIEgens with twisted molecular geometry and molecular rotors shall be superb candidates to design novel luminescent MOFs with smart responsiveness. [ 22,23,32–36 ]…”