Computationally engineering optoelectronic properties and photocatalytic performance in graphene quantum dot/platinum(II) complex photocatalysts

[Display omitted] •Utilizes density functional theory to elucidate structure–function relationships in GQD/platinum photocatalytic nanocomposites.•Reveals substituent selection strategies to optimize light absorption, charge dynamics, reactivity and energy conversion efficiency.•GQD incorporation amplifies substituent effects through additional charge transfer pathways.•Provides guidance for computational engineering of efficient visible-light photocatalysts. This study delves into the impact of various substituents on bipyridyl Pt(II) bisstilbenylacetylide complexes when attached to Graphene quantum dots (GQDs), a material with promising photocatalytic potential. Using density functional theory calculations, the research uncovers that the substituents significantly alter properties of the resulting nanocomposites. These include the geometric and electronic structures, optical absorption profiles, charge transfer configurations, and chemical reactivity. Electron-withdrawing groups cause blueshifts in absorption peaks, while electron-donating ones induce redshifts. These shifts are more pronounced when the complexes are attached to GQDs. The attachment of GQDs also impacts the molecular orbital structure, stabilizing the highest occupied molecular orbital (HOMO), but destabilizing the lowest unoccupied molecular orbital (LUMO). Furthermore, the incorporation of GQDs into the composite enhances overall stability while diminishing reactivity. The formation of the nanocomposite reduces the energetic favorability of electron injection and regeneration processes. Interestingly, the substituents affect the charge transfer length more significantly for nanocomposites compared to isolated complexes. Overall, this study provides valuable insights into fine-tuning optoelectronic and photocatalytic properties of GQD hybrid photocatalysts, useful in applications like solar energy conversion and pollutant degradation. These findings significantly advance the understanding of the structure–function relationship in GQD nanocomposites for photocatalysis.