Molecular All-Mortise-and-Tenon Frameworks towards Luban Lock

Stacking interactions between molecules are central to the field of crystalline molecular materials. To precisely investigate the impact of structural variations on their properties, the most rational approach involves controlling the stacking of molecules with diverse substituents in an identical geometric configuration. However, this idealized scenario encounters formidable obstacles in practical synthesis. Thus, a central question revolves around the feasibility of discovering novel non-covalent or non-coordinated interactions that possess fixed connection modes, maintaining the directional assembly of molecules into identical geometric configurations. Inspired by the traditional wooden mortise and tenon structure, which combines the features of directional precision allowing for intricate wooden pieces to intertwine seamlessly and forming connections that endure rigorous use, we report the first series of crystalline and stable molecular frameworks entirely constructed by mortise-and-tenon joints (MTF-1, MTF-2, and MTF-3). Despite functional group diversity, the supramolecular assembly of MTFs remains unchanged, demonstrating their robust capability for directed assembly. A surprising revelation emerged: the ethyl groups imparted a more intricate and intriguing mortise-and-tenon joint to MTF-3. Since the ethyl groups are not coplanar with the benzene groups, they effectively introduce additional "tenons" to MTF-3. Consequently, the ethyl groups on type II mortise-and-tenon joints act as "locking pins", preventing the easy disengagement of type I mortise-and-tenon joints. This intricate structure endows MTF-3 with a fascinating Luban lock-like construction and exceptional mechanical stiffness. Additionally, ethyl groups in MTF-3 enhance intermolecular interactions, facilitating the separation and transport of photogenerated charge carriers. Ultimately, MTF-3 demonstrates superior photocatalytic H2O2 activity compared to its counterpart, MTF-2 and MTF-1. This groundbreaking discovery pioneers the molecular all mortise-and-tenon frameworks, vastly enriching the crystalline molecular material portfolio.