Decoupled rigid–flexible synergistic assembly in robust hydrogen-bonded organic frameworks for directional proton transport

Abstract

Developing proton-conducting materials that simultaneously exhibit high conductivity and robust structural stability remains a central challenge for clean energy technologies such as proton exchange membrane fuel cells. Hydrogen-bonded organic frameworks (HOFs) provide a versatile platform owing to their designable hydrogen-bond networks, yet precise regulation of proton-transport pathways without sacrificing framework robustness is still limited. Herein, we report a decoupled rigid–flexible synergistic assembly strategy for constructing robust HOFs with directional proton-transport behavior. By combining a rigid tetraaniline-based building unit with linear disulfonate components of different flexibility, two HOFs, HOF-FJU-356 and HOF-FJU-357, were successfully constructed. Structural analyses reveal that both frameworks possess well-defined one-dimensional channels stabilized by charge-assisted N–H⁺⋯⁻O–S hydrogen bonds, while variations in the flexible components lead to distinct channel environments and water-organization modes. As a result, HOF-FJU-356 exhibits a more developed hydrogen-bonded network and delivers a proton conductivity of 1.22 × 10⁻² S cm⁻¹ at 70 °C and 98% relative humidity, which is approximately one order of magnitude higher than that of HOF-FJU-357. Both materials demonstrate excellent chemical and thermal stability under harsh conditions. This work highlights the effectiveness of design-level decoupling of rigidity and flexibility in regulating channel environments, water organization, and proton-transport behavior, offering a general strategy for the development of stable and efficient proton-conducting HOFs.