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 using N-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 CO₂ adsorption of Cu-Mg-Al LDHs were investigated, and the kinetics of the CO₂ adsorption and the photocatalytic reduction of CO₂ were 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 CO₂ capture and adsorption. The CO₂ adsorption capacity of Cu-Mg-Al N was 1.82 mmol·g^-1 at 30 °C and a 0.1 MPa pure CO₂ atmosphere. The kinetic model confirmed that CO₂ adsorption 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 CO₂ to methanol with Cu²⁺ as an active site, which can significantly improve the CO₂ adsorption and photocatalytic conversion.