Photocatalytic Hydrogen Production from Glycerol Aqueous Solutions as Sustainable Feedstocks Using Zr-Based UiO-66 Materials under Simulated Sunlight Irradiation

There is an increasing interest in developing cost-effective technologies to produce hydrogen from sustainable resources. Herein we show a comprehensive study on the use of metal-organic frameworks (MOFs) as heterogeneous photocatalysts for H-2 generation from photoreforming of glycerol aqueous solutions under simulated sunlight irradiation. The list of materials employed in this study include some of the benchmark Zr-MOFs such as UiO-66(Zr)-X (X: H, NO2, NH2) as well as MIL-125(Ti)-NH2 as the reference Ti-MOF. Among these solids, UiO-66(Zr)-NH2 exhibits the highest photocatalytic H-2 production, and this observation is attributed to its adequate energy level. The photocatalytic activity of UiO-66(Zr)-NH2 can be increased by deposition of small Pt NPs as the reference noble metal co-catalyst within the MOF network. This photocatalyst is effectively used for H-2 generation at least for 70 h without loss of activity. The crystallinity of MOF and Pt particle size were maintained as revealed by powder X-ray diffraction and transmission electron microscopy measurements, respectively. Evidence in support of the occurrence of photoinduced charge separation with Pt@UiO-66(Zr)-NH2 is provided from transient absorption and photoluminescence spectroscopies together with photocurrent measurements. This study exemplifies the possibility of using MOFs as photocatalysts for the solar-driven H-2 generation using sustainable feedstocks.

Automated summary

This study demonstrates the possibility of using metal-organic frameworks (MOFs) as heterogeneous photocatalysts for hydrogen generation from sustainable resources. Among the MOFs tested, UiO-66(Zr)-NH2 exhibited the highest photocatalytic activity due to its suitable energy level. The photocatalytic activity of UiO-66(Zr)-NH2 can be further enhanced by incorporating small Pt nanoparticles as co-catalysts. The results provide evidence of photoinduced charge separation with Pt@UiO-66(Zr)-NH2, suggesting the potential of MOFs as photocatalysts for solar-driven hydrogen generation.