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

Hydrogen-bonded organic frameworks (HOFs), self-assembled from strategically pre-designed molecular tectons with complementary hydrogen-bonding patterns, are rapidly evolving into a novel and important class of porous materials. In addition to their common features shared with other functionalized porous materials constructed from modular building blocks, the intrinsically flexible and reversible H-bonding connections endow HOFs with straightforward purification procedures, high crystallinity, solution processability, and recyclability. These unique advantages of HOFs have attracted considerable attention across a broad range of fields, including gas adsorption and separation, catalysis, chemical sensing, and electrical and optical materials. However, the relatively weak H-bonding interactions within HOFs can potentially limit their stability and potential use in further applications. To that end, this Perspective highlights recent advances in the development of chemically and thermally robust HOF materials and systematically discusses relevant design rules and synthesis strategies to access highly stable HOFs.

Structural Aspects of Rubidium Ion Selectivity by Tribenzo-21-crown-7(1)(a)

The structural origins of the selectivity of rubidium ion over other alkali metal ions by tribenzo-21-crown-7 is investigated from single-crystal X-ray diffraction: data for Cs(tribenzo-21-crown-7)(NO(3)), monoclinic, P2(1)/c, a = 9.598(2) Å, b = 23.466(3) Å, c = 23.973(5) Å, beta = 93.31(1) degrees, V = 5390(2) Å(3), Z = 8; data for [Rb(4,4'-bis-tert-butylbenzo,benzo-21-crown-7)(dioxane)(1.5)(H(2)O)(0.18)][Cl].(dioxane)1.82(H(2)O), triclinic, P&onemacr;, a = 11.687(3) Å, b = 12.800(4) Å, c = 17.680(3) Å, alpha = 75.31(2) degrees, beta = 80.01(2) degrees, gamma = 69.09(2) degrees, V = 2379.8(10) Å(3), Z = 2; data for Na(4,4'-bis-tert-butylbenzo,benzo-21-crown-7)ReO(4).0.5(i-PrOH), monoclinic, P2(1)/c, a = 24.300(5) Å, b = 14.066(3) Å, c = 22.676(5) Å, beta = 108.06(3) degrees, V = 7369(3) Å(3), Z = 8; data for and 4,4'-bis-tert-butylbenzo,benzo-21-crown-7, monoclinic, P2(1)/n, a = 16.427(2) Å, b = 11.3675(9) Å, c = 33.137(3) Å, beta = 94.469(8) degrees, V = 6169.0(10) Å(3), Z = 8. The structures reported here are the first reported for a tribenzo-21-crown-7, and the alkali metal ion complexes are the first reported structures of these ions with any 21-crown-7 ether. Different crown conformations are observed for each structure. Molecular mechanics calculations were performed on all conformers, and the results are related to the observed extraction selectivity for rubidium.