题目 Title

Clay Edges Are Dynamic Proton-Conducting Networks Modulated by Structure and pH

期刊 Journal

Journal of Physical Chemistry Letters (IF=5.1)

作者 Author

Feng, Y. X.; Advincula, X. R.; Fang, H. W.; Schran, C.

摘要 Abstract

Montmorillonite, a ubiquitous clay mineral, plays a vital role in geochemical and environmental processes due to its chemically complex edge surfaces. However, the molecular-scale acid–base reactivity of these interfaces remains poorly understood due to the limitations of both experimental resolution and conventional simulations. Here, we employ machine learning potentials with first-principles accuracy to perform nanosecond-scale molecular dynamics simulations of montmorillonite nanoparticles across a range of pH. Our results reveal clear amphoteric behavior, with edge sites undergoing protonation in acidic environments and deprotonation in basic conditions, accompanied by pH-dependent surface charge regulation. Even at neutral pH, spontaneous and directional proton transfer events are common, proceeding via both direct and solvent-mediated pathways. These findings demonstrate that montmorillonite edges are not static arrays of hydroxyl groups but dynamic, proton-conducting networks whose reactivity and charge state are modulated by local structure and solution conditions. This work offers a molecular-level framework for understanding proton transport and buffering in clay–water systems, with broad implications for catalysis, ion exchange, and environmental remediation.

简介 Brief introduction

蒙脱石作为一种广泛存在的黏土矿物，由于其边缘表面具有复杂的化学组成，在地球化学与环境过程中发挥着重要作用。然而，受限于实验分辨率以及传统模拟方法能力，关于这类界面在分子尺度上的酸碱反应性仍缺乏清晰认识。本文采用具有第一性原理精度的机器学习势函数，对不同 pH 条件下的蒙脱石纳米颗粒开展了纳秒尺度的分子动力学模拟。结果表明，蒙脱石边缘表面呈现出明显的两性行为：在酸性环境中发生质子化，在碱性条件下发生去质子化，并伴随着随 pH 变化的表面电荷调节行为。即使在中性 pH 条件下，自发且具有方向性的质子转移也普遍存在，既可通过直接转移路径发生，也可通过溶剂介导的路径发生。上述结果表明，蒙脱石边缘表面并非羟基基团的静态排列，而是由局部结构与溶液条件共同调控反应性与电荷状态的动态质子传导网络。该工作为理解黏土–水体系中的质子传递与缓冲机制提供了分子层面的理论框架，对催化、离子交换以及环境修复等领域亦具有广泛意义。

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