Photocatalytic Hydrogen Production from Glycerol Aqueous Solutions as Sustainable Feedstocks Using Zr-Based UiO-66...

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 H₂ 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 H₂ 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 H₂ 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 H₂ generation using sustainable feedstocks.