Unprecedented aluminum molecular ring based-layer with tailorable optical limiting effect†

The uncontrolled assembly of Al(III) octahedra makes the synthesis of related two-dimensional (2D) compounds unpredictable, thus limiting their potential applications. In contrast to traditional synthesis methods, we propose a stepwise synthetic approach based on aluminum molecular rings. By fine-tuning the angle of the coordination unit and direction of anchoring modulation, a zero-dimensional (0D) aluminum molecular ring (AlOC-196) can be successfully preserved as a unique building block, allowing for the construction of a targeted 2D configuration (AlOC-197). Notably, the weak interlayer interactions facilitate its further exfoliation process. Moreover, compared to bulk crystals, nanosheets produced through liquid-phase exfoliation exhibit enhanced third-order nonlinear optical (NLO) properties. This coordination-driven self-assembly strategy shows promise in expanding the structural diversity and functionality of layered materials.