Accelerating Nickel-Based Molecular Construction via DFT Guidance for Advanced Photocatalytic Hydrogen Production

Understanding the nickel-based molecular catalyst structure and functional relationship is crucial for catalytic hydrogen production in aqueous solutions. Density functional theory (DFT) provides mature theoretical knowledge for efficient catalyst design, significantly reducing catalyst synthesis time and energy consumption. In the present work, three molecular catalysts, Ni(qbz)(pys)₂ (qbz = 2-quinoline benzimidazole) (NQP 1), Ni(qbo)(pys)₂ (qbo = 2-quinoline benzothiazole) (NQP 2), and Ni(pbz)(pys)₂ (pbz = 4-chloro-2,2-pyridylbenzimidazole) (NQP 3) (pys = 2-mercaptopyridine), were designed and synthesized and exhibit a high performance for H₂ generation in aqueous solution with a lamp (λ ≥ 400 nm) under visible light irradiation. Under the optimal conditions, a H₂ evolution rate as high as 1190 μmol h^-1 can be obtained over 25 mg of NQP 1 with the best catalytic performance. DFT has been adopted in this study to unveil the relationship between the ligand qbz and catalyst NQP 1─an efficient step in the design of catalysts with an excellent catalytic performance. We show that, in addition to the presence of the triphenyl ring increasing the overall electron density, rapid electron transfer (ET) from excited fluorescein (Fl) to NQP 1 significantly improves the chance of photogenerated electrons transferring to the active site, ultimately increasing the catalytic activity for H₂ production. This work on understanding the correlation between structures and properties of complexes provides a new idea for manufacturing high-performance photocatalysts.