Interpenetration Isomerism in Triptycene‐Based Hydrogen‐Bonded Organic Frameworks

We describe an example of “interpenetration isomerism” in three‐dimensional hydrogen‐bonded organic frameworks. By exploiting the crystallization conditions for a peripherally extended triptycene H₆PET, we can modulate the interpenetration of the assembled frameworks, yielding a two‐fold interpenetrated structure PETHOF‐ 1 and a five‐fold interpenetrated structure PETHOF‐ 2 as interpenetration isomers. In PETHOF‐ 1 , two individual nets are related by inversion symmetry and form an interwoven topology with a large guest‐accessible volume of about 80 %. In PETHOF‐ 2 , five individual nets are related by translational symmetry and are stacked in an alternating fashion. The activated materials show permanent porosity with Brunauer‐Emmett‐Teller surface areas exceeding 1100 m² g^?1. Synthetic control over the framework interpenetration could serve as a new strategy to construct complex supramolecular architectures from simple organic building blocks.     

Designing Hydrogen‐Bonded Organic Frameworks (HOFs) with Permanent Porosity

Designing organic components that can be used to construct porous materials enables the preparation of tailored functionalized materials. Research into porous materials has seen a resurgence in the past decade as a result of finding of self‐standing porous molecular crystals (PMCs). Particularly, a number of crystalline systems with permanent porosity that are formed by self‐assembly through hydrogen bonding (H‐bonding) have been developed. Such systems are called hydrogen‐bonded organic frameworks (HOFs). Herein we systematically describe H‐bonding patterns (supramolecular synthons) and molecular structures (tectons) that have been used to achieve thermal and chemical durability, a large surface area, and functions, such as selective gas sorption and separation, which can provide design principles for constructing HOFs with permanent porosity.     

An Ultrastable and Easily Regenerated Hydrogen‐Bonded Organic Molecular Framework with Permanent Porosity

A robust hydrogen‐bonded organic framework HOF‐TCBP (H₄TCBP=3,3′,5,5′‐tetrakis‐(4‐carboxyphenyl)‐1,1′‐biphenyl) has been successfully constructed and structurally characterized. It possesses a permanent 3D porous structure with a 5‐fold interpenetrated dia topological network. This activated HOF‐TCBP has a high BET surface area of 2066 m² g⁻¹ and is capable of highly selective adsorption and separation of light hydrocarbons under ambient conditions. It shows excellent thermal stability, as demonstrated by PXRD experiments and N₂ adsorption tests. Practical use of HOF‐TCBP is facilitated by the ease of its preparation and renewal through rotary evaporation.     

Docking Strategy To Construct Thermostable,Single‐Crystalline,Hydrogen‐Bonded Organic Framework with High Surface Area

Enhancing thermal and chemical durability and increasing surface area are two main directions for the construction and improvement of the performance of porous hydrogen‐bonded organic frameworks (HOFs). Herein, a hexaazatriphenylene (HAT) derivative that possesses six carboxyaryl groups serves as a suitable building block for the systematic construction of thermally and chemically durable HOFs with high surface area through shape‐fitted docking between the HAT cores and interpenetrated three‐dimensional network. A HAT derivative with carboxybiphenyl groups forms a stable single‐crystalline porous HOF that displays protic solvent durability, even in concentrated HCl, heat resistance up to 305 °C, and a high Brunauer–Emmett–Teller surface area [SA_(BET)] of 1288 m² g⁻¹. A single crystal of this HOF displays anisotropic fluorescence, which suggests that it would be applicable to polarized emitters based on robust functional porous materials.     

A Hydrogen‐Bonded Hexagonal Buckybowl Framework

A hydrogen‐bonded two‐dimensionally networked buckybowl architecture is presented. Two types of hexagonal network (HexNet) structures ( CPSM‐1 and CPSM‐2 ) have been achieved based on a sumanene derivative ( CPSM ) possessing 4,4′‐dicarboxy‐o ‐terphenyl groups in the periphery. CPSM‐1 has a waved HexNet structure with an alternate alignment of upward and downward bowls. CPSM‐2 has a bilayered HexNet structure composed of hamburger‐shaped dimers of the bowls. This demonstrates that non‐planar π‐systems can be networked two‐dimensionally by an appropriate supramolecular synthon to achieve structurally well‐defined unique bumpy π‐sheets. Furthermore, we revealed that CPSM‐2 undergoes anisotropic shrinking along the c axis by 11 % under high pressure conditions (970 MPa). The shrinkage is brought about by offset sliding between bumpy π‐surfaces of the bilayered HexNet sheets.     

Chirality Synchronization of Hydrogen‐Bonded Complexes of Achiral N‐Heterocycles

2,4‐Diamino‐6‐phenyl‐1,3,5‐triazines carrying a single oligo(ethylene oxide) (EO) chain form an optically isotropic mesophase composed of a conglomerate of macroscopic chiral domains with opposite sense of chirality even though the constituent molecules are achiral. This mesophase was proposed to result from the helical packing of hydrogen‐bonded triazine aggregates, providing long‐range chirality synchronization. The results provide first evidence for macroscopic achiral symmetry breaking upon conglomerate formation in an amorphous isotropic phase formed by hydrogen‐bonded associates of simple N‐heterocycles that are related to prebiotic molecules.