Breaking the Single-Turnover Limit of Photoinduced Ligand Displacement on 2D Semiconductor Nanoplatelets

On zero-dimensional (0D) colloidal quantum dots, photoinduced ligand dissociation is fundamentally capped at one event per photoexcited particle: once a ligand leaves as a radical anion, Coulombic repulsion with the residual hole blocks a second electron transfer. Here, we show that two-dimensional (2D) CdSe nanoplatelets (NPLs) overcome this single-turnover limit. NPL excitation delivers multiple electrons to coordinated perylene bisimide (PBI) ligands, sequentially ejecting more than one PBI radical anion per nanocrystal and raising the photodisplacement yield 7-fold over 0D analogues. Transient-absorption, flash-photolysis, and assembly-resolved experiments identify the [100] basal plane as the active facet and show that efficiency is set by the number of PBI ligands that fall within the NPL exciton diffusion range─a reaction volume that can be tuned through lateral size and ligand coverage rather than through thermodynamic driving force or shell permeability. The result reframes 2D semiconductor NPLs as tunable multielectron photoreactors for programmable surface chemistry.