Abstract
Controlled assembly of two-dimensional (2D) supramolecular organic frameworks (SOFs) has been demonstrated through a binary strategy in which 1,4-bis-(4-(3,5-dicyano-2,6-dipyridyl)pyridyl)naphthalene (2), generated in situ by oxidative dehydrogenation of 1,4-bis-(4-(3,5-dicyano-2,6-dipyridyl)dihydropyridyl)naphthalene (1), is coupled in a 1:1 ratio with terphenyl-3,3′,4,4′-tetracarboxylic acid (3; to form SOF-8), 5,5′-(anthracene-9,10-diyl)diisophthalic acid (4; to form SOF-9), or 5,5′-bis-(azanediyl)-oxalyl-diisophthalic acid (5; to form SOF-10). Complementary O–H···N hydrogen bonds assemble 2D 63-hcb (honeycomb) subunits that pack as layers in SOF-8 to give a three-dimensional (3D) supramolecular network with parallel channels hosting guest DMF (DMF = N,N′-dimethylformamide) molecules. SOF-9 and SOF-10 feature supramolecular networks of 2D → 3D inclined polycatenation of similar hcb layers as those in SOF-8. Although SOF-8 suffers framework collapse upon guest removal, the polycatenated frameworks of SOF-9 and SOF-10 exhibit excellent chemical and thermal stability, solvent/moisture durability, and permanent porosity. Moreover, their corresponding desolvated (activated) samples SOF-9a and SOF-10a display enhanced adsorption and selectivity for CO2 over N2 and CH4. The structures of these activated compounds are well described by quantum chemistry calculations, which have allowed us to determine their mechanical properties, as well as identify their soft deformation modes and a large number of low-energy vibration modes. These results not only demonstrate an effective synthetic platform for porous organic molecular materials stabilized solely by primary hydrogen bonds but also suggest a viable means to build robust SOF materials with enhanced gas uptake capacity and selectivity.
Highlights
Porous organic molecular solids have been proposed as a new platform of chemical materials
Supramolecular organic frameworks (SOFs),[11−18] which are structurally mimetic of the well-known metal organic frameworks (MOFs),[19−23] define porous crystalline molecular solids built from organic constituents assembled through supramolecular interactions
We have demonstrated a rational design strategy to prepare 2D binary supramolecular organic framework (SOF) materials assembled via complementary hydrogen bonding interactions
Summary
Porous organic molecular solids have been proposed as a new platform of chemical materials. The importance of dimensionality and well-defined in-plane crystallinity of two-dimensional (2D) materials is well established,[28,29] and structural diversity of 2D molecular networks comes from the molecular assembly and from the different packing arrangements possible for these nets.[29,33] In contrast to 3D SOFs,12−18 2D SOFs assembled solely through hydrogen bonds rarely exhibit both structural robustness and significant adsorption capacity in the solid state With this in mind, we sought to construct thermally and chemically stable 2D SOF materials for selective adsorption of carbon dioxide (CO2) using a new binary strategy. (w), 1418 (w), 1393 (m), 1269 (s), 1114 (w), 1061 (w), 1022 (w), Crystal Growth & Design
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