Anion-Directed Stacking Engineering in 2D Metal-Organic Frameworks Built From Silver(I) and Propeller-Chiral...

Precise control over interlayer stacking in two-dimensional (2D) materials is a powerful strategy for modulating functional properties. Yet how racemic assemblies of enantiopure layers influence the full spectrum of AA, AB, and ABC stacking patterns has remained unexplored. Here, we uncover this missing link with a family of cationic 2D metal-organic frameworks, MOF-CC-2(X), built from a propeller-chiral, tris-triazole click-cage ligand (CC-2), and Ag(I)-triazole coordination. The ligand's dual 1,3,5-triphenyltriazine faces offer orthogonal π-surfaces that respond to the identity and interactions of charge-balancing anions (X = PF₆ ^-, OTf^-, NO₃ ^-). Systematic anion substitution directs the formation of eclipsed AA, paired AABBCC, or fully alternating ABC stacking, further assisted by modulation of π···π interactions. In particular, the solvated NO₃ ^- anions disrupt triazine stacking and reduce interlayer cohesion, enabling exfoliation into ultrathin nanosheets (≤ 5 nm) that preserve chiral registry between homochiral layers. These positively charged, π-rich nanosheets show rapid, selective uptake of sulfonated dyes in water, demonstrating Langmuir-type adsorption and excellent recyclability. This study establishes (1) counteranion identity as a primary driver of stacking in 2D MOFs, (2) racemic layer chirality as a structural design element, and (3) propeller cages as versatile modules for programmable exfoliation and water remediation.