Preparation Of P-Aminobenzoic Acid Grafted TiO_x Semiconductive Aerogels For Photocatalytic Reduction Of CO₂ To Methanol

Large emission of CO₂ have a serious impact on the environment.The use of sustainable solar energy to convert CO₂ into fuel such as methanol is a hot research topic.Organic-inorganic hybrid materials have attracted extensive attention in photocatalysis.For Metal Organic Framework materials and organic sensitized TiO₂ materials,organic functional groups can act as photosensitizers to absorb visible light and generate charge transfer from ligand to metal ion（LMCT）,however,the ratio of ligand to metal ion is usually fixed.Inspired by organic-inorganic hybrid materials used as catalysts,we prepared p-aminobenzoic acid（PABA）grafted TiO_x semiconductor aerogels with adjustable ratios of organic ligands to metal ions.In addition,2-Aminoterephthalic Acid was used as ligand to prepare grafted aerogel and NH₂-MIL-125（Ti）materials for comparison.In this work,the p-aminobenzoic acid was used as ligand and Ti Cl₄ as metal ion precursor,p-aminobenzoic acid（PABA）grafted TiO_x semiconductive aerogels were successfully prepared by sol-gel method under the condition of freeze drying and characterized by N₂ physisorption,FT-IR,SEM,TG,XPS,UV-Vis DRS,PL and etc.The aerogels show a strong absorption of visible light and the large surface area.The absorption edges of the aerogel gradually red shifted with the increase of the grafting amount of the PABA,the band gap of aerogels decreased to 2.06e V.Meanwhile,the porosity of the aerogel was also changeable with the composition.When the molar ratio of the grafted PABA to Ti was 0.56,the aerogel had a BET surface area of was 264.1 m²g^-1,the average pore size was 7.7 nm,and the pore volume was 0.46 cm³g^-1.Correspondingly,the aerogel had a narrow band gap of 2.07 e V with a low PL intensity.Photocatalytic reduction of CO₂ was carried out in 150 m L of 0.2 M ethylenediamine（EDA）aqueous solution under irradiation by a 300 W Xe lamp.The methanol yield reached 4090μmol/g-cat for 4 hours of reaction time.Comparatively,2-Aminoterephthalic acid（NH₂-BDC）was used as the organic ligand to prepare the grafted TiO_xaerogel and NH₂-MIL-125（Ti）.