In Situ Fabrication of TiO2 Nanoparticles/2D Porphyrin Metal-Organic Frameworks for Enhancing the Photoreduction of CO2 to CO

Abstract

Developing photocatalysts for CO2 reduction with high efficiency and selectivity in a photocatalytic system remains urgent yet challenging. Herein, we report photocatalyzed highly selective reduction of CO2 to CO by in-situ growth of ultrafine TiO2 nanoparticles on an ultrathin two-dimensional (2D) porphyrin metal-organic framework (Al-MOF@TiO2). Al-MOF and TiO2 nanoparticles are connected by 4, 4-bipyridine (BPY), and the pyridine nitrogen atom in the structure of BPY on the one hand coordinates with the metal aluminum in Al-MOF and on the other hand coordinates with TiO2 to form Ti-O-N bond. The ultrathin 2D architecture of the Al-MOF ensures improved dispersibility and stability of TiO2 under prolonged light illumination. Additionally, the interfacial Ti-O-N covalent bond promotes charge carrier transfer and separation along with rapid migration of charge carriers to the surface toward the selective reduction of CO2 to CO. The hybrid photocatalyst demonstrated excellent capability in reducing CO2 to CO with a selectivity of 94.1%, producing 1901 μmol•g⁻¹ of CO, which is 8 times higher than that of Al-MOF alone. Furthermore, the Al-MOF@TiO2 photocatalyst exhibited superior stability, maintaining its structural integrity in an aqueous reaction system. This work provides an effective strategy for improving the stability and charge separation property of metallic oxide modified photocatalyst toward efficient photocatalytic CO2 reduction.