Rational Design of a Metal-Organic Framework for Water Capture via Linkers with Embedded Hydrophilic Atoms

Water scarcity remains a critical global challenge, driving the need for efficient technologies that can capture water directly from the atmosphere. Among various adsorbents, metal-organic frameworks (MOFs) have shown great promise for water capture owing to their tunable pore structures and chemical functionalities. In this work, a linker functionalization strategy incorporating embedded hydrophilic atoms was employed to design a new MOF, LMRC-2 (LMRC = Lanzhou Magnetic Resonance Center). LMRC-2 exhibits over a 10-fold increase in water uptake at low relative humidity (RH) compared to that of its hydrophobic parent MOF, while maintaining a comparable total capacity at high RH. Solid-state NMR spectroscopy provided direct evidence that the pyrrolic nitrogen atoms in the linker act as strong water adsorption sites. These results highlight the effectiveness of rational linker modification for tuning the hydrophilicity of MOFs and demonstrate that solid-state NMR can be a powerful probe for elucidating water adsorption mechanisms in porous materials.