Small-Molecule Photocatalytic Activation Through Noncovalent Interactions.

Supramolecular chemistry explores how noncovalent interactions enable the association of multiple molecular components into structurally defined and functionally active assemblies, with molecular recognition arising from geometric, electronic, and chemical complementarity. Integrating these principles with photocatalysis is reshaping organic synthesis by introducing adaptive control over reactivity under visible light. Through Hbonding (hydrogen bonding), π-π stacking, host-guest encapsulation, charge-transfer complexation, hydrophobic effects, and σ-hole interactions (cation-π, anion-π, and halogen bonding), supramolecular photocatalysts dynamically organize substrates and modulate excited-state properties, thereby influencing reaction pathways and selectivity. Such assemblies can respond to changes in substrate identity, aggregation state, or irradiation conditions, enabling tunable and metal-free photochemical transformations. Inspired by biological photosystems, spatial confinement and electronic communication within supramolecular architectures further unlock unconventional reactivity beyond classical photocatalysis. This review article summarizes recent mechanistic insights and design strategies, positioning supramolecular photocatalysis as a versatile and sustainable platform for next-generation catalytic synthesis.