Sigmoidally hydrochromic molecular porous crystal with rotatable dendrons

Open-[60]fullerenols with water adsorbed both inside and outside

The water affinity on [60]fullerenols was found to be governed by surface electrostatic potential while water aggregation is initiated by the hydroxy groups attached on the carbon surface. The molecular water adsorption at the internal sphere caused a significnat inhibition of water adsorption at the external carbon surface.

Paper-Derived Millimeter-Thick Yarn Supercapacitors Enabling High Volumetric Energy Density

Solid-state supercapacitors have shown extraordinary promise for flexible and wearable electronics. To date, they are still limited by relatively poor energy volumetric performances, which are largely determined by the pore structures and physicochemical properties of electrode materials. Moreover, the poor mechanical properties afforded because of the intrinsic shortcomings of electrode materials need to be resolved. Herein, we designed a flexible and solid-state yarn electrode with high porosity and high affinity toward electrolytes using poly(3,4-ethylenedioxythiophene) (PEDOT) and Korean heritage paper (KHP). To maximize the volumetric capacitive energy storage, PEDOT-loaded conductive KHP sheets (two-dimensional) were transformed into a biscrolled yarn (one-dimensional) via simple twisting. The volumetric capacitance of the biscrolled yarn supercapacitors with 1 mm cell diameter exhibited a volumetric specific capacitance of ∼6576 mF/cm³ at a scan rate of 25 mV/s, which is attributable to the high mass loading of PEDOT as a conductive support and increased packing density. Moreover, multiple optimized yarn supercapacitors can be connected to yield a total length of 1 m, demonstrating enormous potential as a portable and wearable power supply for operating smartwatches.

Tunable Fluorescence in Two-Component Hydrogen-Bonded Organic Frameworks Based on Energy Transfer

A dumbbell-shaped compound (TPAD) with four 2,4-diaminotriazine moieties as H-bond units and a benzene ring as a bridge group was found to form hydrogen-bonded organic frameworks (HOFs) with strong cyan fluorescence. An energy acceptor, 6,6',6″,6‴-(((benzo[c][1,2,5]thiadiazole-4,7-diylbis-(4,1-phenylene))bis(azanetriyl))tetrakis(benzene-4,1-diyl))tetrakis(1,3,5-triazine-2,4-diamine) (BTAD), with the same molecular skeleton as TPAD and a longer emission wavelength could homogeneously distribute within the framework of TPAD through occupying the locations of TPAD. As a result, two-component HOFs (TC-HOFs) were formed. The nonradiative energy transfer from TPAD as the donor to BTAD as the acceptor happens within frameworks owing to the efficient spectral overlap between the emission of TPAD and the absorption of BTAD. Moreover, the emission wavelengths and colors of TC-HOFs could be easily and continuously modulated by the content of the acceptor. The fluorescence color changed from cyan to orange when the content of BTAD gradually increased. This finding affirms that TC-HOFs with continuously adjustable composition can be constructed from two molecules with the same molecular skeleton, and highly efficient nonradiative energy transfer may happen in porous TC-HOFs. To the best of our knowledge, these TC-HOFs are the first example of TC-HOFs involved in energy transfer.

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

Organic porous crystals from small and non-cyclic organic molecules can be constructed by various intermolecular weak interactions. Owing to their precise stacking types, intermolecular interaction and pore microstructure, the relationship...

Solvophobicity-directed assembly of microporous molecular crystals

Dense packing is a universal tendency of organic molecules in the solid state. Typical porous crystals utilize reticular strong intermolecular bonding networks to overcome this principle. Here, we report a solvophobicity-based methodology for assembling discrete molecules into a porous form and succeed in synthesizing isostructural porous polymorphs of an amphiphilic aromatic molecule Py₆Mes. A computational analysis of the crystal structure reveals the major contribution of dispersion interaction as the driving force for assembling Py₆Mes into a columnar stacking while the columns are sterically salient and form nanopores between them. The porous packing is facilitated particularly in solvents with weak dispersion interaction due to the solvophobic effect. Conversely, solvents with strong dispersion interaction intercalate between Py₆Mes due to the solvophilic effect and provide non-porous inclusion crystals. The solvophobicity-directed polymorphism is further corroborated by the polymorphs of Py₆Mes-analogues, m-Py₆Mes and Ph₆Mes.

Vapochromism of Organic Crystals Based on Macrocyclic Compounds and Inclusion Complexes

Vapochromic materials, which change color and luminescence when exposed to specific vapors and gases, have attracted considerable attention in recent years owing to their potential applications in a wide range of fields such as chemical sensors and environmental monitors. Although the mechanism of vapochromism is still unclear, several studies have elucidated it from the viewpoint of crystal engineering. In this mini-review, we investigate recent advances in the vapochromism of organic crystals. Among them, macrocyclic molecules and inclusion complexes, which have apparent host–guest interactions with analyte molecules (specific vapors and gases), are described. When the host compound is properly designed, its cavity size and symmetry change in response to guest molecules, influencing the optical properties by changing the molecular inclusion and recognition abilities. This information highlights the importance of structure–property relationships resulting from the molecular recognition at the solid–vapor interface.