Correlating Nanomechanical Behavior and Adsorption Performance in a Serendipitously Assembled Two-Dimensional Hydrogen-Bonded Organic System

Hydrogen-bonded organic systems (<b>HBOS</b>) combine facile synthesis, solution processability, regenerability, and water stability, making them attractive for the design of functional materials. Motivated by the limited report on chiral <b>HBOS</b>, we explored the hydrothermal assembly of melamine (<b>M</b>) and l-glutamic acid (<b>L-GA</b>) and unexpectedly yielded a crystalline 2D melamine-cyanuric acid (<b>M-CA</b>) adduct. In this transformation, <b>L-GA</b> served both as an acid catalyst promoting partial in situ hydrolysis of <b>M</b> to cyanuric acid (<b>CA</b>), and as a structure-directing agent, facilitating the <b>M-CA</b> self-assembly. Nanoindentation revealed that <b>M-CA</b> exhibits significantly higher penetration depths than those of <b>M</b> and <b>CA</b>, consistent with its layered packing and presence of hollow hexagonal channels. In contrast, <b>M</b> displayed the highest elastic modulus and hardness due to its rigid herringbone packing. Energy framework analysis linked the nanomechanical behavior of the crystals to the differences in hydrogen-bonding strength and topology. Functionally, <b>M-CA</b> demonstrated superior guest adsorption (rhodamine B 96.75 mg g^-1 and methyl orange 102.50 mg g^-1) with excellent recyclability over multiple cycles, outperforming both <b>M</b> and <b>CA</b> by ∼4-fold. These results establish a correlation between the structure of <b>HBOS</b>, nanomechanical properties, and adsorption performance, offering insights into the design of hydrogen-bonded functional materials.