ZIF-8/Zn2GeO4nanorods with an enhanced CO2adsorption property in an aqueous medium for photocatalytic synthesis of liquid fuel

Abstract

The photoreduction of CO₂ on inorganic semiconductors has been researched for several decades, but the conversion efficiency is still low due to the recombination of photo-generated electron–hole pairs, low utilization efficiency of solar energy and weak adsorption of CO₂. Here we for the first time demonstrate that metal–organic frameworks such as ZIF-8 can effectively adsorb CO₂ dissolved in water, and promote photocatalytic activity of a semiconductor catalyst in CO₂ reduction into liquid fuels in an aqueous medium. In particular, Zn₂GeO₄/ZIF-8 hybrid nanorods were successfully synthesized by growing ZIF-8 nanoparticles on Zn₂GeO₄ nanorods. The Zn₂GeO₄/ZIF-8 nanocomposite inherits both high CO₂ adsorption capacity of ZIF-8 nanoparticles and high crystallinity of Zn₂GeO₄ nanorods. The Zn₂GeO₄/ZIF-8 hybrid nanorods containing 25 wt% ZIF-8 exhibit 3.8 times higher dissolved CO₂ adsorption capacity than the bare Zn₂GeO₄ nanorods, resulting in a 62% enhancement in photocatalytic conversion of CO₂ into liquid CH₃OH fuel. The strategy reported here is promising for developing more active photocatalysts for improving CO₂ conversion efficiency by taking advantage of excellent adsorption property of metal–organic frameworks in aqueous media.