氮化硼纳米片负载Pd(OAc)2催化剂的制备及催化微波辅助Heck反应

以液相超声剥离的氮化硼纳米片(BNNSs)为载体, 通过表面羟基、 氨基、 席夫碱共价功能化后与Pd ²⁺配位, 制备负载型催化剂Pd@BNNSs-Schiff, 并将该催化剂应用于微波辅助的Heck反应. 通过傅里叶红外光谱(FTIR)、 激光拉曼(Raman)光谱、 X射线衍射(XRD)、 同步热分析(TGA)、 X射线光电子能谱(XPS)、 扫描电子显微镜(SEM)、 透射电子显微镜(TEM)和元素分布分析(EDS mapping)对催化剂的结构和形貌进行了表征. 结果表明, 当苯乙烯与碘苯摩尔比为1.25∶1, 溶剂为N,N-二甲基甲酰胺, 缚酸剂为三乙胺, 催化剂Pd用量为0.08%(质量分数)时, 以450 W功率微波辐射20 min收率最高为95.6%; 催化活性明显优于以相同方法制备的催化剂Pd@GO-Schiff(78.3%)(GO=氧化石墨烯); Pd@BNNSs-Schiff循环利用6次后仍具有较高的催化活性,参照催化剂在循环3次后活性明显降低, 7次后失活.

Synthesis of Boron Nitride Nanosheets Supported Pd(OAc)2 and the Catalytic Microwaves-assisted Heck Reactions

Using h-BN as starting material, BNNSs were prepared by liquid phase exfoliation, then BNNSs-Schiff were synthesized through surface hydroxylation, amination and aldimine condensation reaction. Pd@BNNSs-Schiff were obtained by complexing BNNSs-Schiff with Pd ²⁺. The structure and morphology of the catalyst were characterized by means of Fourier transform infrared spectroscopy(FTIR), laser-Raman spectrum, X-Ray diffraction(XRD), thermogravimetric analyzer(TGA), X-Ray photoelectron spectroscopy(XPS), scanning electron microscopy(SEM), transmission electron microscopy(TEM), elemental distribution analysis(EDS mapping). The Pd@BNNSs-Schiff composite was used for microwave-assisted Heck reaction and the optimized conditions were investigated. When the molar ratio of styrene and iodobenzene was 1.25∶1, the dosage of catalyst(Pd) was 0.08%, and the highest yield of 1,2-diphenylethylene was 96.5% with N,N-dimethylformamide formide as solvent, triethylamine as acid-binding agent under 450 W power microwave irradiation for 20 min. The cataly-tic activity was significantly better than the Pd@GO-Schiff(78.3%) prepared by the same method. Furthermore, the catalytic performance of Pd@BNNSs-Schiff maintained a high level after 6 cycles, but that of Pd@GO-Schiff decreased sharply after 3 cycles and was inactived after 7 cycles.