Polarity‐Evolution Control and Luminescence Regulation in Multiple‐Site Hydrogen‐Bonded Organic Frameworks

Abstract

Hydrogen-bonded organic frameworks (HOFs) have shown great potential in separation, sensing and host-guest chemistry, however, the pre-design of HOFs remains challenging due to the uncertainty of solvents' participation in framework formation. Herein, the polarity-evolution-controlled framework/luminescence regulation is demonstrated based on multiple-site hydrogen-bonded organic frameworks. Several distinct HOFs were prepared by changing bonding modes of building units via the evolution of electrostatic forces induced by various solvent polarities. High-polar solvents with strong electrostatic attraction to surrounding units showed the tendency to form cage structures, while low-polar solvents with weak electrostatic attraction only occupy hydrogen-bond sites, conducive to the channel formation. Furthermore, the conformation of optical building unit can be adjusted by affecting the solvent polarity, generating different luminescence outputs. These results pave the way for the rational design of ideal HOFs with ondemand framework regulation and luminescence properties.

Subtle Structural Variations within Solvent-Free D–A-Type Organic Crystals for Tuning Emission Wavelength up to 47 nm Shift

“…The above results indicate that we successfully achieved fluorescence modulation through solvent regulation in dense organic crystal frameworks with subtle structural variations. The maximum tuneable range of emission peaks of the four solvent-induced isomorphism dense frameworks is 47 nm, which is notably different from previous studies that relied on solvent infiltration into pore structures to modulate organic crystal luminescence. ,− …”

“…The precise control of luminescence wavelengths in organic crystal materials is of paramount importance to meet the diverse demands across various domains. − Through the careful selection of construction units, adjustment of donor–acceptor distances, − control over crystal structure, codoping, , and manipulation of external conditions, such as temperature, , pressure, and solvent type, ,− arises the precise modulation of the fluorescence wavelength . In particular, solvents usually play a significant role in determining the lattice composition of porous HOFs and can act as structure-directing agents, resulting in distinct crystal structures with different luminescent properties. − Although the luminescence regulation strategies of organic crystal materials have been extremely extensive, the control of luminescence shifts in solvent-free dense isomorphism frameworks through the manipulation of the crystallization mother liquor is exceptionally rare.…”

Recent progress in gas separation platforms based on hydrogen-bonded organic frameworks (HOFs)

“…However, the structural fragility and low stability caused by the relatively weak hydrogen bonding qualities commonly hinder the creation of strong HOFs with persistent porosity. 66–69 Few HOFs have been observed to have a porosity that persists in the solid state, and even fewer can withstand adverse circumstances. 70–72 Therefore, the development of HOFs for practical applications is severely hampered by the lack of stability and permanent porosity.…”

Hydrogen-bonded organic framework with tailored pores prepared by enlarging the core size for high-performance Xe/Kr separation

“…[17][18][19][20] The design of HOFs can be achieved by altering the combination of the cores of monomer molecules and hydrogen-bonding linkers. 21 Up to now, various H-bonding linkers have been explored for the assembly of HOFs, such as carboxylic acid, 22,23 2,4-diaminotriazine, 24,25 pyrazole, 26,27 pyridine, 28,29 aldehyde, 30,31 and benzene cyanide. 32,33 The benzene cyanide linker is currently attracting considerable attention owing to its ability to provide multiple hydrogen-bonding nodes, and to confer excellent stability and ultramicroporous environment.…”