Stable 2D Heteroporous Covalent Organic Frameworks for Efficient Ionic Conduction

Abstract

Two‐dimensional (2D) covalent organic frameworks (COFs) feature open and ordered one‐dimensional column nanochannels which offer immense possibilities for incorporation of various guests for specific functions. However, the relatively low chemical stability of most COFs originating from the dynamic covalent linkages hinders their practical application. In this work, a highly crystalline and heteroporous dibenzo[g,p]chrysene‐based COF (DBC‐2P) was synthesized and served as a host material for ionic conduction. DBC‐2P exhibits excellent stability both in strong acid and base due to the large conjugated DBC‐based knot that reinforces the interlayer interactions. Subsequent encapsulation of linear polyethylene glycol (PEG) and PEG‐LiBF4 salt into the nanochannels of DBC‐2P affords a hybrid material with a high ionic conductivity of 2.31×10−3 S cm−1. This work demonstrates an efficient post‐synthetic strategy for the development of new COF–polymer composites with intriguing properties.

Dibenzochrysene enables tightly controlled docking and stabilizes photoexcited states in dual-pore covalent organic frameworks

“…This strongly decreased stacking distance (by almost 1.0 Å) for each DBC-containing COF is attributed to the more planar (gently curved) shape of the chrysene building block compared to the more sterically demanding ETTA node. 45 The influence of the linear dialdehyde on the stacking distance is apparently less dominant, though being still detectable.…”

“…This is in excellent agreement with a parallel report illustrating the high crystallinity of Biph-DBC COF. 45,51 Transmission electron microscopy (TEM) micrographs show the highly crystalline nature of the COFs (Fig. S2 †).…”

“…These findings are in line with the reported dihedral angles for ETTA and DBC. 45 As a result, the π-stacking distance between adjacent COF layers is expected to be reduced while the existing DBC torsion angle is still sufficient to enable specific docking effects for the successive layers. This is expected to enable defined π-π-interactions in the stacks and improved π-orbital overlap within the individual layers allowing for extended electron delocalization.…”

“…44 Therefore, the incorporation of DBCTA into a framework is expected to drastically reduce the steric constraints for stacking, allowing for more closely packed molecular assemblies. 45 In addition, the DBC core and its derivatives exhibit attractive photophysical properties and charge carrier mobilities. 44,46,47 This combination of properties is promising for the realization of highly ordered materials based on the DBC nodes with encoded features for optoelectronic applications.…”

Structural Approaches to Control Interlayer Interactions in 2D Covalent Organic Frameworks

“…Chen and co‐workers have explored D 2h ‐symmetric dibenzo[ g,p ]chrysene (DBC) monomers in imine‐linked COFs (DBC–TIM, Figure ). [ 48 ] DBC is a fused analog of the propeller‐shaped ETTA monomer, [ 28 ] which is slightly twisted as the result of steric congestion of its cove edges. The transamination reaction of DBC–TIM and 4,4′‐biphenyldicarbaldehyde produced a highly crystalline imine‐linked COF (DBC‐2P) with excellent stability in strong base and acid, which was attributed to the tight packing (3.6 Å).…”