In Situ Confinement of 0D Halometallates Within Deep Eutectic Solvents: From Systematic Screening to Metal‐Tunable Luminescence for Anti‐Counterfeiting Eutectogels

ABSTRACT Despite the promising microenvrionments of deep eutectic solvents (DESs), including their charge‐rich nature, tunable polarity, and microviscosity, the role of neat DESs as photonic media has remained largely underexplored, often relying on the addition of ex situ‐synthesized luminophores to produce photoluminescence (PL). Here, we report a photostable, metal ion (M n+ )‐tunable luminescent DES platform driven by the in situ formation of zero‐dimensional (0D) halometallates stabilized within a designed hydrogen bond network. Combinatorial screening of hydrogen bond acceptors and donors identifies an efficient pair for stabilizing highly emissive 0D chloroplumbate(II) complexes under ambient conditions, achieving a PL quantum yield (PLQY) of 60.2%. Moreover, this DES matrix generates versatile emission with customizable excitation and emission wavelengths, PL lifetimes, and PLQYs…