Precise control over the isomorphic self-assembly of nanocluster superstructures via weak interactions remains a fundamental challenge in materials science, primarily due to the lack of directional guidance. Inspired by the ancient mortise-and-tenon joint, we herein report a series of crystalline nanocluster superstructures (MTC-1 and MTC-2) that were exclusively assembled by such molecular joints, representing the first paradigm of its kind. Despite alterations in functional groups (methyl and ethyl), the supramolecular packing motif remains invariant, underscoring the robustness of this directed assembly strategy. Notably, the ethyl groups in MTC-2 serve as “locking pins”, resulting in MTC-2 a fascinating Luban lock-like construction. This ingenious design endows MTC-2 with enhanced photogenerated charge migration and superior O₂ adsorption capability, achieving a record-high photocatalytic H₂O₂ production rate (19,978 μmol·g⁻¹·h⁻¹) among all isolated crystalline cluster-based materials, an order-of-magnitude enhancement over existing benchmarks. This work not only presents a record-breaking photocatalyst but also establishes a general assembly strategy, the mortise-and-tenon joint, which is expected to guide the rational design of functional superstructures across diverse nanocluster systems.