Silica-Supported Phosphonic Acids as Thermally and Oxidatively Stable Organic Acid Sites
作者:Alexandre Charmot、Andrew Solovyov、Antonio G. DiPasquale、Alexander Katz
DOI:10.1021/acs.chemmater.6b02027
日期:2016.9.13
treated with pyridine at room temperature were strong enough acids to protonate pyridine at room temperature as exhibited by a distinct pyridinium cation band in the infrared spectrum; however, in contrast to much stronger acid sites in silica-supported phosphoric acid materials, almost all adsorbed pyridine was lost by 150 °C. Use of a stronger base for acid-site titration consisting of diisopropylamine
描述了由有机膦酸负载的二氧化硅材料C3 / SiO 2和C4 / SiO 2组成的有机无机材料,其中C3为丙烷1,2,3-三膦酸和C4是丁烷-1,2,3,4-四膦酸。使用单晶X射线衍射分析了这两种膦酸的固态结构,这些数据显示出广泛的分子间氢键且没有分子内氢键。热重分析/质谱(TGA / MS)数据表明,这些材料在低于400°C的空气中缺乏燃烧,仅释放出低于150°C的可逆有机膦酸缩合的水。合成了一系列由二氧化硅支撑的比较材料,其中包括有机膦酸CX8(代表杯芳烃大环,在上下边缘均装饰有高密度的有机膦酸取代基)和聚乙烯基磷酸(PVPA))。CX8 / SiO 2材料在空气中的热稳定性和燃烧温度均低得多,在空气中为300°C,而PVPA具有与C3和C4相当的热稳定性。TGA结合碱探针滴定法用于确定在各种覆盖率和温度下所有二氧化硅负载的膦酸的布朗斯台德酸位点密度。材料C4 / SiO 2 -37%