Unlocking Water Adsorption Mechanisms in Y-BTC MOF: Insights from XAFS and SSNMR Spectroscopy

Water plays a critical role in natural and technological processes, including atmospheric water harvesting, electrocatalysis, and biochemical reactions, all of which involve interactions between water and materials. Metal–organic frameworks (MOFs), with their tunable porosity and adsorption sites, offer significant potential in these fields. Understanding the interactions of water with MOFs is essential for optimizing their performance. This study investigates water adsorption behavior and dynamics in a yttrium-based MOF (Y-BTC) with open metal sites using X-ray absorption fine structure (XAFS) spectroscopy, solid-state nuclear magnetic resonance (SSNMR), and Monte Carlo (MC) simulations. XAFS reveals local structural changes upon coordinated water removal, producing open metal sites, while SSNMR provides insights into water mobility and adsorption site preferences under varying relative humidity (RH) conditions. MC simulations further validate these findings by mapping the water distribution within the framework. The results highlight that water adsorption in Y-BTC involves multiple adsorption sites and dynamic rearrangements, with the framework itself undergoing subtle structural evolution at lower temperatures. These findings enhance our understanding of water adsorption mechanisms in MOFs and offer valuable insights for the rational design of materials for water harvesting.