Light‐Controlled Reversible Coassembly of Hybrid Functional Nanostructures

Reversible coassembly of hybrid low‐dimensional nanostructures offers a route to tunable materials for sensing, separation, delivery, and catalysis. However, many functional nanoscale building blocks are stabilized by aromatic ligands and suffer from poor solubility, intermolecular π stacking, and limited chemical stability. Here, a light‐controlled platform is introduced that couples photoisomerizable azobenzene ligands with polycyclic aromatic hydrocarbon (PAH)‐functionalized counterparts to switch the interparticle coupling in heterogeneous mixtures. The strategy uses complementary electron‐rich and electron‐deficient sites generated on different nanocomponents, providing mild charge‐transfer interactions that drive reversible coassembly, while maintaining the balance between attractive and repulsive forces. Using this mechanism, nanocomposites are prepared including gold NPs with magnetite (Fe 3 O 4 ) NPs and gold NPs with carbon nanotubes. An external magnetic field can further direct Fe 3 O 4 ‐containing hybrids and enables noninvasive separation. This system requires no chemical additives, and produces on‐demand transitions with photo‐modulated optical and magnetic responses, advancing stimuli‐responsive assembly beyond conventional electrostatic, thermal, solvent, or redox controls.