Preparation of Amine-Modified Cu-Mg-Al LDH Composite Photocatalyst

Cu-Mg-Al layered double hydroxides (LDHs) with amine modification were prepared by an organic combination of an anionic surfactant-mediated method and an ultrasonic spalling method usingN-aminoethyl-γ-aminopropyltrimethoxysilane as a grafting agent. The materials were characterized by elemental analysis, XRD, SEM, FTIR, TGA, and XPS. The effects of the Cu2+content on the surface morphology and the CO2adsorption of Cu-Mg-Al LDHs were investigated, and the kinetics of the CO2adsorption and the photocatalytic reduction of CO2were further analyzed. The results indicated that the amine-modified method and appropriate Cu2+contents can improve the surface morphology, the increase amine loading and the free-amino functional groups of the materials, which were beneficial to CO2capture and adsorption. The CO2adsorption capacity of Cu-Mg-Al N was 1.82 mmol·g−1at 30 °C and a 0.1 MPa pure CO2atmosphere. The kinetic model confirmed that CO2adsorption was governed by both the physical and chemical adsorption, which could be enhanced with the increase of the Cu2+content. The chemical adsorption was suppressed, when the Cu2+content was too high. Cu-Mg-Al N can photocatalytically reduce CO2to methanol with Cu2+as an active site, which can significantly improve the CO2adsorption and photocatalytic conversion.