Interfacial hydrogen bonding and quantum confinement synergistically control triplet-energy-transfer-mediated photocatalysis by perovskite nanocrystals

Triplet-energy-transfer (TET) photocatalysis by semiconductor nanocrystals (NCs) relies on short-range Dexter transfer across the NC-substrate interface, making catalytic efficiency highly sensitive to both NC photophysics and substrate organization. While lead halide perovskite NCs have recently emerged as potent triplet sensitizers, current strategies largely rely on carboxylate-mediated substrate anchoring to facilitate interfacial TET. Generalizable substrate-organization strategies and their interplay with quantum confinement in governing photocatalytic reactivity remain unresolved. Here, we demonstrate that CsPbBr₃ NCs catalyze TET-mediated [2 + 2] photocycloaddition of chalcone derivatives and reveal that interfacial hydrogen bonding and quantum confinement synergistically govern photocatalytic reactivity. Native ammonium ligands of the NCs promote substrate recognition through hydrogen-bonding interactions, organizing chalcone substrates at the NC surface without covalent anchoring. Stern-Volmer analysis and transient absorption spectroscopy reveal pronounced size-dependent TET dynamics, with quantum-confined NCs exhibiting substantially enhanced triplet sensitization. These effects translate directly into photocatalytic performance, enabling efficient intermolecular photocycloadditions of diverse chalcone derivatives and selective heterocoupling with alkene partners through preferential chalcone sensitization. Control experiments further demonstrate that efficient photocatalysis requires both interfacial hydrogen bonding and quantum confinement. This work establishes an interfacial design principle for perovskite-NC triplet photocatalysis and provides new insight into controlling energy-transfer reactions at semiconductor nanocrystal interfaces.