Preparation of p-aminobenzoic acid grafted TiOx semiconductive aerogels for photocatalytic reduction of CO2 to methanol

Abstract

Organic–inorganic hybrid materials have attracted extensive attention in photocatalysis. In this work, p-aminobenzoic acid (PABA) grafted TiO_x semiconductive aerogels were successfully prepared and characterized by N₂ physisorption, FT-IR, SEM, TG, XPS, UV-vis DRS, PL, etc. The aerogels showed strong absorption of visible light. The absorption edges of the aerogels gradually red shifted with the increase of the grafting amount of PABA. Meanwhile, the porosity of the aerogels could also be changed with the composition. When the molar ratio of the grafted PABA to Ti was 0.56, the aerogel had a BET surface area of 264.1 m² g⁻¹, the average pore size was 7.7 nm, and the pore volume was 0.46 cm³ g⁻¹. Correspondingly, the aerogel had a narrow band gap of 2.07 eV with a low PL intensity. Its conductivity was 0.0085 μS mm⁻¹. Photocatalytic reduction of CO₂ was carried out in 150 mL of 0.2 M ethylenediamine (EDA) aqueous solution under irradiation by a 300 W Xe lamp. The methanol yield reached 4090 μmol g-cat⁻¹ within 4 h of irradiation. Comparatively, the methanol yield over the NH₂-MIL-125(Ti) 2040 μmol g-cat⁻¹.