2D-Covalent Organic Frameworks with Interlayer Hydrogen Bonding Oriented through Designed Nonplanarity

• Published in: Journal of the American Chemical Society Vol. 142; no. 30; pp. 12987 - 12994
• Main Authors: Alahakoon, Sampath B, Tan, Kui, Pandey, Haardik, Diwakara, Shashini D, McCandless, Gregory T, Grinffiel, Daniel I, Durand-Silva, Alejandra, Thonhauser, Timo, Smaldone, Ronald A
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 29.07.2020; Amer Chemical Soc; American Chemical Society (ACS)
• Subjects: Amides; Chemistry; Chemistry, Multidisciplinary; Covalent organic frameworks; Crystallinity; Layers; MATERIALS SCIENCE; Noncovalent interactions; Physical Sciences; Science & Technology; POLYMERS; PLANARITY; COVALENT; STABILITY; GROWTH; CRYSTALLINE; INSIGHT; INFRARED TEMPERATURE
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.0c03409

We report the synthesis and characterization of a new class of 2D-covalent organic frameworks, called COFamides, whose layers are held together by amide hydrogen bonds. To accomplish this, we have designed monomers with a nonplanar structure that arises from steric crowding, forcing the amide side groups out of plane with the COF sheets orienting the hydrogen bonds between the layers. The presence of these hydrogen bonds provides significant structural stabilization as demonstrated by comparison to control structures that lack hydrogen bonding capability, resulting in lower surface area and crystallinity. We have characterized both azine and imine-linked versions of these COFs, named COFamide-1 and -2, respectively, for their surface areas, pore sizes, and crystallinity. In addition to these more conventional characterization methods, we also used variable temperature infrared spectroscopy methods and van der Waals density functional calculations to directly observe the presence of hydrogen bonding.