Guest-Regulated Luminescence and Force-Stimuli Response of a Hydrogen-Bonded Organic Framework

Abstract

Guest molecules may endow porous materials with new or enhanced properties as well as functions. Here, a porous hydrogen-bonded organic framework (HOF) constructed from a three-armed triphenylamine derivative is used to investigate how guests regulate photoluminescence and trigger force-stimuli response. It was found that guest solvents in pores might regulate HOF's luminescence. Interestingly, acetic acid as a guest endowed HOF materials with longer emission wavelengths and triggered the responses to mechanical force stimuli. Under shear force, an obvious blueshift in emission spectra was observed because of the loss of free guests and the conversion of πstacking model. Further blue-shifted emission appeared while the bound guests were completely removed by heating. Mechanofluorochromic HOF materials could be regenerated through recrystallization and adsorbing guest. Conversely, HOFs with other guests and activated HOFs only resulted in a slight change in their fluorescence behaviors after force stimuli.

Design Rules of Hydrogen-Bonded Organic Frameworks with High Chemical and Thermal Stabilities

“…Through the rational design of organic building blocks with geometric symmetry, planar molecules with diverse π-conjugated systems can coordinate to each other through intermolecular H-bonding interactions to form a single layer, and multiple layers pack together through strong π–π-stacking interactions to form a 3D framework with one-dimensional (1D) channels throughout the structure. HOFs that contain large, π-conjugated aromatic molecules as building blocks exhibit significantly enhanced thermal stabilities and increased chemical resistance to organic solvents and acidic or basic aqueous solutions due to the inert reactivity of the tectons (Figure ) (see refs , , , , , , − , − , − , , , , , , , − , , , , , − , , , − ). Several groups have independently demonstrated that HOFs with shape-fitted π–π-stacking interactions not only show type III stability upon desolvation but also become even more stable as the effective π–π-stacking areas become larger (Table ).…”

Luminescent organic porous crystals from non-cyclic molecules and their applications

“…8a) to investigate how guests regulate photoluminescence and trigger force-stimuli response. 73 In the crystals, double H-bonds between DAT units firstly help molecules to form 2D H-bonded framework layers with two kinds of pores, and then the 2D layers were linked by intermolecular hydrogen bonds and π-stacking to form the HOF, X-HOF-1, with 1D wave-shaped channels along the c axis (Fig. 8b).…”

“…Insets are the photos of samples under UV light. (d) Photos of HOFs with HOAc after grinding and heating under UV light.Reprinted with permission 73. Copyright 2021 American Chemical Society.…”

Reversible On–Off Switching of Excitation-Wavelength-Dependent Emission of a Phosphorescent Soft Salt Based on Platinum(II) Complexes

“…Under different external stimuli, such as light, − mechanical force, − vapor, − electric field, − or temperature, − materials that can exhibit a reversible change in their optical properties have huge application potentials within various optoelectronic fields. Among these types of optical materials, excitation-wavelength-dependent (Ex-De) luminophores have attracted particular interest. − This is due to the facile, fast, and noninvasive manipulation of their luminescence color by varying the excitation energy; such systems demonstrate great promise in bioimaging and anticounterfeiting applications .…”