Boosting CO2 photoreduction via a ternary plasmonic ZIF-8/Au NPs/TiO2 nanocomposite with synergistic plasmonic and adsorptive effects

The photocatalytic conversion of CO 2 into solar fuels presents a sustainable approach to alleviate climate change and address energy crisis. To address the limitations of conventional photocatalysts, such as their restricted visible-light response and rapid charge recombination, we have developed a ternary nanocomposite consisting of zeolitic imidazolate framework-8 (ZIF-8), plasmonic gold nanoparticles (Au NPs), and titanium dioxide (TiO 2 ). In this system, ZIF-8 provides high-density CO 2 adsorption sites, enhancing the local concentration of CO 2 and facilitating its subsequent reduction. The incorporation of Au NPs induces a strong localized surface plasmon resonance (LSPR) effect, significantly broadening the visible-light harvesting capability of the composite and promoting efficient charge transfer between TiO 2 and ZIF-8. TiO 2 serves as a stable photocatalytic platform, enabling effective charge separation and transfer. Comprehensive characterization verifies the uniform integration of the three components and the formation of close interfacial contacts. The ternary nanocomposite demonstrates significantly improved visible-light absorption, reduced charge recombination, and enhanced photogenerated carrier separation and transfer, as supported by UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL), electrochemical impedance spectroscopy (EIS), and photocurrent measurements. Under simulated sunlight, the ZIF-8/Au/TiO 2 photocatalyst achieves CO 2 -to-fuel conversion rates of 1.56 μmol g −1  h −1 for methane (CH 4 ) and 4.65 μmol g −1  h −1 for carbon monoxide (CO). This enhancement is attributed to the synergistic effects of plasmonic sensitization by Au nanoparticles and CO 2 adsorption enrichment by ZIF-8, which collectively enhance photon utilization, reactant concentration, and interfacial charge transfer dynamics.