Hydrogen-bonded porous organic crystals are promising candidates for functional organic materials due to their easy construction and flexibility arising from reversible bond formation-dissociation. However, it still remains challenging to form porous materials with void spaces that are well-controlled in size, shape, and multiplicity because even well-designed porous frameworks often fail to generate pores within the crystal due to unexpected disruption of hydrogen bonding networks or interpenetration of the frameworks. Herein, we demonstrate that a series of C3-symmetric π-conjugated planar molecules (Tp, T12, T18, and Ex) with three 4,4'-dicarboxy-o-terphenyl moieties in their periphery can form robust hydrogen-bonded hexagonal networks (H-HexNets) with dual or triple pores and that the H-HexNets stack without interpenetration to yield a layered assembly of H-HexNet (LA-H-HexNet) with accessible volumes up to 59%. Specifically, LA-H-HexNets of Tp and T12 exhibit high crystallinity and permanent porosity after desolvation (activation): SABET = 788 and 557 m(2) g(-1), respectively, based on CO2 sorption at 195 K. We believe that the present design principle can be applied to construct a wide range of two-dimensional noncovalent organic frameworks (2D-nCOFs) and create a pathway to the development of a new class of highly porous functional materials.

Smaller can be better: The first example of meta-quinodimethane embedded in an indenofluorene framework has been synthesized. 10,12-Dimesitylindeno[2,1-b]fluorene exhibits extremely low-energy light absorption, despite the small conjugation space of the molecule, which consists of only 20 π electrons.

The construction and precise control of the face-to-face π-stacked arrangements of anthracene fluorophores in the crystalline state led to a remarkable red shift in the fluorescence spectrum due to unprecedented excited oligomer formation. The arrangements were regulated by using organic salts including anthracene-1,5-disulfonic acid (1,5-ADS) and a variety of aliphatic amines. Because of the smaller number of hydrogen atoms at the edge positions and the steric effect of the sulfonate groups, 1,5-ADS should prefer face-to-face π-stacked arrangements over the usual edge-to-face herringbone arrangement. Indeed, as the alkyl substituents were lengthened, the organic salts altered their anthracene arrangement to give two-dimensional (2D) edge-to-face and end-to-face herringbone arrangements, one-dimensional (1D) face-to-face zigzag and slipped stacking arrangements, a lateral 1D face-to-face arrangement like part of a brick wall, and a discrete monomer arrangement. The monomer arrangement behaved as a dilute solution even in the close-packed solid state to emit deep blue light. The 1D face-to-face zigzag and slipped stacking of the anthracene fluorophores caused a red shift of 30-40 nm in the fluorescence emission with respect to the discrete arrangement, probably owing to ground-state associations. On the other hand, the 2D end-to-face stacking induced a larger red shift of 60 nm, which is attributed to the excimer fluorescence. Surprisingly, the brick-like lateral face-to-face arrangement afforded a remarkable red shift of 150 nm to give yellow fluorescence. This anomalous red shift is probably due to excited oligomer formation in such a lateral 1D arrangement according to the long fluorescence lifetime and little shift in the excitation spectrum. The regulation of the π-stacked arrangement of anthracene fluorophores enabled the wide modulation of the fluorescence and a detailed investigation of the relationships between the photophysical properties and the arrangements.

The first example of a porous molecular crystal containing rotors is presented. The permanently porous crystal architecture is sustained by rotor-bearing molecular rods which are connected through charge-assisted hydrogen bonds. The rotors, as fast as 10(8) Hz at 240 K, are exposed to the crystalline channels, which absorb CO2 and I2 vapors at low pressure. The rotor dynamics could be switched off and on by I2 absorption/desorption, showing remarkable change of material dynamics by the interaction with gaseous species and suggesting the use of molecular crystals in sensing and pollutant management.