Imidazole-Linked Crystalline Two-Dimensional Polymer with Ultrahigh Proton-Conductivity

Abstract

Proton-exchange membrane fuel cells are promising energy devices for a sustainable future due to green features, high power density, and mild operating conditions. A facile proton-conducting membrane plays a pivotal role to boost the efficiency of fuel cells, and hence focused research in this area is highly desirable. Major issues associated with the successful example of Nafion resulted in the search for alternate proton conducting materials. Even though proton carrier loaded crystalline porous organic frameworks have been used for proton-conduction, the weak host–guest interactions limited their practical use. Herein, we developed a crystalline 2D-polymer composed of benzimidazole units as the integral part, prepared by the condensation of aryl acid and diamine in polyphosphoric acid medium. The imidazole linked-2D-polymer exhibits ultrahigh proton conductivity (3.2 × 10–2 S cm–1) (at 95% relative humidity and 95 °C) in the pristine state, which is highest among the undoped porous organic frameworks so far reported. The present strategy of a crystalline proton-conducting 2D-polymer will lead to the development of new high performing crystalline solid proton conductor.

Confining H3PO4 network in covalent organic frameworks enables proton super flow

“…H 3 PO 4 @TPB-DMeTP-COF enables a proton flow that is even twofold compared to molten neat H 3 PO 4 (~1 × 10 -1 S cm -1 ) 25 . Note that the proton flow is significantly increased by 2-8 orders of magnitude higher than those of other analogues under anhydrous condition (Table 1) 3,5,6,10,21,[26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] . Meta-organic frameworks (MOFs) are hardly efficient to construct anhydrous proton-conducting systems by loading neat H 3 PO 4 into their pores.…”

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

“…A special case of the amide linkages are the imidazole linkages, which can be formed from an ortho diamine and a carboxylic acid synthesized in pyrophosphoric acid, where the highly acidic conditions ensure the reversibility of the reaction. 50 This linkage offers highly stable materials, but the harsh reaction conditions limit the substrate scope for this linkage.…”

Vertical two-dimensional layered fused aromatic ladder structure

“…2c) related to carbon (C 1 s), nitrogen (N 1 s) and oxygen (O 1 s), without any other elements. Deconvolution of the N 1 s resulted in two peaks, associated with the tertiary N and C=N-C at 400.6 and 398.5 eV, repectively 32 . This supports the formation of the benzimidazole rings again (Inset of Fig.…”