Polycatenated 2D Hydrogen-Bonded Binary SupramolecularOrganic Frameworks (SOFs) with Enhanced Gas Adsorption and Selectivity

摘要

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 adsorptionand selectivity for CO2 over N2 and CH4. The structures of these activated compounds are well describedby quantum chemistry calculations, which have allowed us to determinetheir mechanical properties, as well as identify their soft deformationmodes and a large number of low-energy vibration modes. These resultsnot only demonstrate an effective synthetic platform for porous organicmolecular materials stabilized solely by primary hydrogen bonds butalso suggest a viable means to build robust SOF materials with enhancedgas uptake capacity and selectivity.