Gao Hui, Zhang Hao, Zhang Jian, Lu Ning-Yue, Yu Ling, Zhang Xian-Ming
Shanxi Provincial Department-Municipal Key Laboratory Cultivation Base for Quality Enhancement and Utilization of Shangdang Chinese Medicinal Materials, School of Pharmacy, Changzhi Medical College, Changzhi, 046000, P.R. China.
Key Laboratory of Magnetic Molecules and Magnetic Information Material of Ministry of Education, School of Chemistry and Material Science, Shanxi Normal University, Taiyuan, 030006, P.R. China.
Angew Chem Int Ed Engl. 2025 Sep 2:e202512366. doi: 10.1002/anie.202512366.
The strategic modulation of proton transport kinetics and precise control of migration energy barriers in metal-organic frameworks (MOFs) are essential for developing next-generation proton conductors. Inspired by biological proton channels, this study introduces a dynamic regulation strategy by keto-enol tautomerism to reconcile the intrinsic trade-off between low activation energy (E) and sustained proton mobility. We successfully construct a hierarchical proton conductive system (denoted as FU@MOF-808-SOH) by integrating 5-fluorouracil (5-FU) molecules into sulfonic-functionalized MOF-808 through a two-step post-synthetic modification. The enol tautomer of 5-FU reconfigures hydrogen-bond networks under humidity variations, synergizing with anchored ─SOH groups to establish proton transport pathways along ordered ionic channels (─SOH···HO···5-FU) and tautomerism-driven delocalization via reversible keto-enol isomerization. The optimized compound FU@MOF-808-SOH exhibits a high proton conductivity of 7.15 × 10 S cm at 353 K and 95% RH, representing an approximate 300-fold enhancement over pristine MOF-808, a 15-fold improvement versus the 5-FU-encapsulated analogue FU@MOF-808, and the sulfonated framework MOF-808-SOH. Density functional theory (DFT) calculations elucidate an ultra-low formation energy barrier (9.05 and 1.59 kcal mol) from keto to enol conversion, attributed to sulfonic acid stabilization of protonated transition states. Furthermore, the proton conductive mechanism is visually corroborated by molecular dynamic (MD) simulation, suggesting Grotthuss-dominated proton migration within hydrated nanochannels, aligning with experimental results.
金属有机框架（MOF）中质子传输动力学的战略调控以及迁移能垒的精确控制对于开发下一代质子导体至关重要。受生物质子通道的启发，本研究引入了一种通过酮 - 烯醇互变异构的动态调节策略，以协调低活化能（E）与持续质子迁移率之间的内在权衡。我们通过两步后合成修饰将5 - 氟尿嘧啶（5 - FU）分子整合到磺酸功能化的MOF - 808中，成功构建了一种分级质子传导系统（记为FU@MOF - 808 - SOH）。5 - FU的烯醇互变异构体在湿度变化下重新配置氢键网络，与锚定的─SOH基团协同作用，沿着有序离子通道（─SOH···HO···5 - FU）建立质子传输途径，并通过可逆的酮 - 烯醇异构化实现互变异构驱动的离域。优化后的化合物FU@MOF - 808 - SOH在353 K和95%相对湿度下表现出7.15×10 S cm的高质子传导率，相较于原始的MOF - 808提高了约300倍，相较于封装5 - FU的类似物FU@MOF - 808以及磺化框架MOF - 808 - SOH提高了15倍。密度泛函理论（DFT）计算阐明了从酮到烯醇转化的超低形成能垒（9.05和1.59 kcal mol），这归因于质子化过渡态的磺酸稳定作用。此外，分子动力学（MD）模拟直观地证实了质子传导机制，表明在水合纳米通道内以Grotthuss机制为主导的质子迁移，与实验结果一致。
