National Nanotechnology Center, National Science and Technology Development Agency , Phaholyothin road, Patumthani 12120, Thailand.
ACS Appl Mater Interfaces. 2017 Apr 12;9(14):12812-12822. doi: 10.1021/acsami.7b03910. Epub 2017 Apr 3.
Polyhedral oligomeric silsesquioxane (POSS)-based materials, poly-POSS-T [n = 8 (1), 10 (2), 12 (3), and mix (4)], were prepared in high yields via free radical polymerization of corresponding pure forms of methacrylate-functionalized POSS monomers, MMA-POSS-T (n = 8, 10, 12), and the mixture form, MMA-POSS-T. Powder X-ray diffraction (XRD) spectra and BET analysis indicate that 1-4 are amorphous materials with high surface areas (683-839 m g). The surface areas and total pore volumes follow the trend: poly-POSS-T > poly-POSS-T > poly-POSS-T > poly-POSS-T. In addition, on the basis of Barrett-Joyner-Halenda (BJH) analysis, poly-POSS-T contains the highest amount of mesopores. The Pd nanoparticles immobilized on poly-POSS-T [n = 8 (5), 10 (6), 12 (7), and mix (8)] are well dispersed with 4-6 wt % Pd content and similar average particle sizes of 6.2-6.5 nm, according to transmission electron microscopy-energy dispersive X-ray analysis (TEM-EDX) and microwave plasma-atomic emission spectroscopy (MP-AES). At 90 °C, the stabilized Pd nanoparticles in 5-8 catalyzed aerobic oxidation of benzyl alcohol to benzaldehyde in 72-100% yields at 6 h using a mixture of a HO/Pluronic (P123) solution. The PdNp@poly-POSS-T catalyst (5) exhibited the lowest catalytic activity, as a result of its lowest surface areas, total pore volumes, and amounts of mesopores. With the catalyst 8, various benzyl alcohol derivatives were converted to the corresponding aldehydes in good to excellent yields. However, with alcoholic substrates featuring electron-withdrawing substituents, high conversions were achieved with 1 equiv of KCO additive and longer reaction times.
多面体低聚倍半硅氧烷（POSS）基材料，聚-POSS-T [n = 8（1）、10（2）、12（3）和混合（4）]，通过相应的纯甲基丙烯酰氧基功能化 POSS 单体 MMA-POSS-T（n = 8、10、12）和混合形式 MMA-POSS-T 的自由基聚合以高产率制备。粉末 X 射线衍射（XRD）谱和 BET 分析表明 1-4 是无定形材料，具有高比表面积（683-839 m2/g）。比表面积和总孔体积遵循以下趋势：聚-POSS-T > 聚-POSS-T > 聚-POSS-T > 聚-POSS-T。此外，基于 Barrett-Joyner-Halenda（BJH）分析，聚-POSS-T 含有最多的中孔。根据透射电子显微镜-能量色散 X 射线分析（TEM-EDX）和微波等离子体原子发射光谱（MP-AES），负载在聚-POSS-T [n = 8（5）、10（6）、12（7）和混合（8）]上的钯纳米粒子具有良好的分散性，钯含量为 4-6wt%，平均粒径为 6.2-6.5nm。在 90°C 下，在 6 小时内使用 HO/Pluronic（P123）溶液的混合物，稳定的 Pd 纳米粒子在 5-8 中催化苄醇有氧氧化生成苯甲醛，产率为 72-100%。PdNp@poly-POSS-T 催化剂（5）表现出最低的催化活性，这是由于其比表面积、总孔体积和中孔数量最低。对于 8 号催化剂，可以将各种苄醇衍生物转化为相应的醛，产率良好至优秀。然而，对于具有吸电子取代基的醇类底物，在添加 1 当量 KCO 和延长反应时间的情况下，可实现高转化率。
