Aminal-Linked Covalent Organic Frameworks through Condensation of Secondary Amine with Aldehyde

Abstract

New linkage chemistry will endow covalent organic frameworks (COFs) with not only structural diversity but also fascinating properties. However, to develop a new type of linkages has been a great challenge. We herein report the first two COFs using aminal as the linkages. These two COFs have been synthesized by condensation of secondary amine and aldehyde. They crystallize in cpi net, which is a new topology for COFs. The aminal linkage is found to favor reservation of photophysical property of the monomers due to its tetrahedral geometry and nonconjugated feature. These aminal-COFs exhibit good thermal stability and high chemical stability under neutral and basic conditions.

Solving the COF trilemma: towards crystalline, stable and functional covalent organic frameworks

“…41 A special case of the imine condensation is the formation of an aminal-linked COF by the use of a secondary rather than a primary amine and an aldehyde. 42 As the piperazine molecules connect two adjacent aldehyde moieties, this type of COF linkage can also be considered to be the first example of a one dimensional secondary building unit, a feature frequently encountered in metal organic frameworks but not in COFs. 43 Instead of a typical amine, an urea functional group can be used in combination with an ortho hydroxy aldehyde, leading to COFs with good stability towards acids.…”

Unravelling Crystal Structures of Covalent Organic Frameworks by Electron Diffraction Tomography

“…As the major maturing field of reticular chemistry, [ 1 ] covalent organic frameworks (COFs) are constructed by reticulating organic building units entirely through strong covalent bonds into extended 2D [ 2 ] and 3D [ 3 ] networks (Figure 1a), as well as 1D molecular weaving structures, [ 4 ] which can be considered as covalent chemistry extended into 3D space with unprecedented molecular precision. [ 5 ] Up to date, COF chemistry has shown generality of covalent linkages, [ 2,6‐20 ] diversity of pore engineering, [ 21‐23 ] and versatility in functional applications. [ 16,21,24‐34 ] Based on properties of large specific surface area, low density and tunable structures, it shows promising applications in fields of molecule storage and separation, [ 35‐39 ] catalysis, [ 40‐46 ] energy storage, [ 20,35,47‐49 ] optoelectronics, [ 50‐54 ] and so on.…”

Aminal/Schiff‐Base Polymer to Fabricate Nitrogen‐Doped Porous Carbon Nanospheres for High‐Performance Supercapacitors

“…Figure S1 shows the solid‐state 13 C NMR spectrum of the polymer. In general, the peaks at 171 ppm and 45 ppm are assigned to the carbon of imine group (C=N) and carbon covalently linked to secondary amine (−NH−CH−NH−) leading to aminal structure . Moreover, the peak at 193 ppm corresponds to the residual aldehyde end group (C=O) from terminal p‐phthalaldehyde unit in the polymer and the signals between 116–149 ppm are assigned to the aromatic carbon .…”

“…On the other hand, evolving new nitrogen‐containing linkage polymer is still one of the driving forces to push the field forward. Aminal‐linkage and the N, N‐acetal are strong enough in the polymer structure . To best of our knowledge, few of reported data has applied it into carbon precursor.…”