Abstract
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, NO(2), NH(2)) as well as MIL-125(Ti)-NH(2) as the reference Ti-MOF. Among these solids, UiO-66(Zr)-NH(2) exhibits the highest photocatalytic H(2) production, and this observation is attributed to its adequate energy level. The photocatalytic activity of UiO-66(Zr)-NH(2) 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)-NH(2) 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.