Cutting COF-like C N to Give Colloidal Quantum Dots: Towards Optical Encryption and Bidirectional Sulfur Chemistry via Functional Group and Edge Effects.

Herein, we report the first synthesis of colloidal C N quantum dots (QDs) and their functional composites and explore their optical activities and edge-selective polysulfide adsorption-catalysis. As-obtained C NQDs are rich in carbonyl groups and edges, allowing good solution processability and facile assembly with other moieties for creating functionalities. While C NQDs show normal fluorescence (FL), the QD/poly(vinyl alcohol) (PVA) composites give FL/room-temperature-phosphorescence (RTP) dual-mode emission, enabling the corresponding solution to be used as an encryption ink. The QDs anchored onto carbon nanotubes can be used as a barrier layer to decorate commercial separators, endowing a Li-S cell with excellent cycling stability, high rate capability, and large areal capacity. Computation and experiment studies show that edge sites in C N favor polysulfide adsorption and catalysis and the enriched edges and carbonyl groups in QDs synergically promotecatalytic conversion of sulfur species.