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

Hydrogen-bonded organic systems (HBOS) 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 HBOS, we explored the hydrothermal assembly of melamine (M) and l-glutamic acid (L-GA) and unexpectedly yielded a crystalline 2D melamine-cyanuric acid (M-CA) adduct. In this transformation, L-GA served both as an acid catalyst promoting partial in situ hydrolysis of M to cyanuric acid (CA), and as a structure-directing agent, facilitating the M-CA self-assembly. Nanoindentation revealed that M-CA exhibits significantly higher penetration depths than those of M and CA, consistent with its layered packing and presence of hollow hexagonal channels. In contrast, M 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, M-CA 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 M and CA by ∼4-fold. These results establish a correlation between the structure of HBOS, nanomechanical properties, and adsorption performance, offering insights into the design of hydrogen-bonded functional materials.