Site Spacing Reconstruction Toward Perfect Hydrogen-Bond Network for Fast Proton Transport

Proton-conducting materials are essential to electrochemical energy storage, conversion and sensing, yet their performance is restricted by structural limitations. A key structural constraint is the architecture-imposed separation between hydrophilic sites, which prevents the formation of fully developed, continuous hydrogen-bond networks and imposes a persistent bottleneck on proton transport. Here, we propose a site spacing reconstruction strategy to strengthen the hydrogen-bond network and validate its effectiveness using a hydrogen-bonded organic framework built from 1,3,5-tris(4-carboxyphenyl)benzene (HOF-BTB) and its Na⁺-modified analogue (Na-HOF-BTB) as a model system. Through electrostatic self-assembly, strongly hydrophilic sites are introduced to shorten the intersite distance and convert long-range water bridges into short-range ones, thereby lowering the energetic barrier for hydrogen-bond network formation. At 97% relative humidity, Na-HOF-BTB exhibits a markedly strengthened hydrogen-bond network, leading to a substantial enhancement of proton conductivity relative to pristine HOF-BTB. The Na-HOF-BTB device achieves a switching ratio of up to approximately 7000, corresponding to a 182-fold improvement over the pristine HOF-BTB device. We further show the generality of this strategy in other HOF systems and demonstrate their representative applications in fruit spoilage surveillance, health management, and pharmaceutical preservation. This work provides a new design principle for high-performance proton-conducting materials.