Photocatalytic Performance of Perovskite and Metal-Organic Framework Hybrid Material for the Reduction of N to Ammonia.

The orthorhombic phase of KNbO perovskite has been applied for nitrogen (N) photoreduction to ammonia (NH). However, this material suffers from a low surface area and low ammonia production efficiency under UV light irradiation. To eliminate these barriers, we used a metal-organic framework (MOF), named as TMU-5 ([Zn(OBA)(BPDH)]·1.5DMF, where HOBA = 4,4'-oxybis(benzoic acid) and BPDH = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene), for the synthesis of the KNbO@TMU-5 hybrid material. KNbO@TMU-5 achieved a NH production rate of 39.9 μmol·L·h·g upon UV light irradiation, as compared to 20.5 μmol·L·h·g recorded for KNbO under similar experimental conditions. Using different characterization techniques especially gas adsorption, cyclic voltammetry, X-ray photoelectron spectroscopy, photocurrent measurements, and Fourier transform infrared spectroscopy, it has been found that the higher photoactivity of KNbO@TMU-5 in ammonia production is due to its higher surface area, higher electron-hole separation efficiency, and higher density of negative charges on Nb sites. This work shows that hybridization of conventional semiconductors (SCs) with photoactive MOFs can improve the photoactivity of the SC@MOF hybrid material in different reactions, especially kinetically complex reactions like photoconversion of nitrogen to ammonia.