(602e) Graphimine - ? New Imine-Linked, Two-Dimensional Covalent Organic Framework

Graphimine is a member of a new class of two-dimensional polymers composed of hexa-substituted benzene nodes within a two-dimensional covalent organic framework (2D COF). Imine-linked and nitrogen containing COFs are emerging as a highly desirable class of materials due to their permeant porosity, periodic structure, thermal and chemical stability, making them desirable for number of applications including separations, energy storage, sensor development, and gas absorption. Graphimine was synthesized from a novel hexa-substituted monomer, 2,4,6-triaminobenzene-1,3,5-tricarbaldehyde (TABTCA). TABTCA was derived from a high yielding, three-step, synthetic pathway, utilizing a substitution reaction with anhydrous ammonia and 2,4,6-tribromobenzene-1,3,5-tricarbaldehyde. Nuclear magnetic resonance spectroscopy was used to successfully confirm its chemical structure, and mass spectrometry verified its molecular weight. Polymerization of TABTCA into graphimine is conducted using reversible, acid-catalyzed polycondensation, that results in imine linkage formation, and structural re-organization via transimination to achieve the 2D COF. Graphimine is analyzed with FTIR, to determine conversion of aldehyde and amine functionalities to imine-linkages; PXRD, to analyze the resulting crystalline structure; and atomic force microscopy, to examine interlayer stacking and morphological structure. Furthermore, graphimine can be oxidized to its amide-linked counterpart, graphamide, which could allow for improved strength and thermal resilience through the formation of interlayer hydrogen bonding networks. Graphimine and graphamide are fabricated into films using techniques such as drop casting, spin-coating, and doctor blading, for applications that require extended sheets or films. These results provide evidence for the first successful production of a highly compacted imine- and amide- linked two-dimensional polymers.