Reducing the excition binding energy of covalent-organic frameworks via spatial-confined NiCo-NC as internal nanoreactors for photocatalytic hydrogen evolution

Abstract

COFs (covalent-organic frameworks) are regarded as ideal photocatalyst for hydrogen-evolution, due to their structural controllability, but they possess poor electrical conductivity and high exciton binding energy, which limits their photocatalytic activity. Here, the NiCo-ZIF-67 derived NiCo-nitrogen-doped carbon (NiCo-NC) with superior conductivity and high light-absorption capacity was spatially confined in the channels of TP-BD COF (TP: 2, 4, 6-triformylphloroglucino; BD: 4, 4′-biphenylenediamin) by constructing hydrogen bonds to form NiCo-NC@TP-BD COF core@shell heterojunctions and NiCo-NC acts as internal highly active nanoreactor, which could accelerate the photocatalytic efficiency. Specifically, the optimal catalyst [email protected] (NT-0.6) exhibits the maximum H₂ evolution rate of 78.97mmol g⁻¹ h⁻¹ without Pt cocatalyst, which is approximately 395 times higher than that of bare TP-BD COF. Systematic investigations imply that the NiCo-NC as a high active nanoreactor was stably encapsulated in the pore of TP-BD by hydrogen bonds and formed a close interfacial contact, which is revealed by Fourier-transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (¹H NMR). Meanwhile, the charge transfer and Hydrogen Evolution Reaction (HER) are revealed by the density functional theory (DFT) calculation. This work offers a promising strategy to reduce the high excitation binding energy of COFs-based catalysts in photocatalytic H₂ evolution.