The ordered growth of semiconductor quantum dots (QDs) in confined environments remains a critical challenge in photocatalysis. Herein, Cs3Bi2Br9 (CBB) QDs were covalently anchored as single-rod nanocrystals (SRNCs) within Hf-based metal–organic framework (MOF) nanosheets (Hf12-bpy, H2bpy = 2,2′-bipyridine-5,5′-dicarboxylic acid), forming a series of host–guest photocatalysts CBB@Hf12-bpy. By modulation of the thickness of MOF nanosheets, the length of CBB SRNCs was effectively shortened to 18 nm, exhibiting strong quantum confinement effects. Mechanistic studies reveal that the bpy-CBB dual-nitrogen chelation effect induces a discrete distribution of CBB within Hf12-bpy pores, and the well-matched interlayer spacing of H2bpy (7.95 Å ≈ dBi···Bi) guides the anisotropic growth of CBB along the 001 direction into SRNCs. Such a long-range-ordered SRNC architecture significantly improves the bulk-to-surface charge separation efficiency, enabling ultrafast electron supply (average charge excitation rate: 5.320 mV). Additionally, the chelated N–Bi–N moieties work as covalent electron-transfer bridges to markedly reduce charge-transfer resistance (7.75 Ω) and interfacial charge-transfer barriers (100.5 meV), accelerating interfacial charge migration kinetics. These synergistic advantages endow CBB@Hf12-bpy(18 nm) with an exceptional electron accumulation rate (1.54 g–1·min–1) and record-breaking CO2-to-CO conversion efficiency (15,982.1 μmol·g–1·h–1) with 100% selectivity. The durability, stability, and potential photocatalytic mechanisms were also systematically investigated.
Ma et al. (Fri,) studied this question.