In this study, carbon dots coated with diluted polyethylene imine was prepared from the carbonization of citric acid (CA) with branched polyethylene imine (BPEI) at temperature (200 °C), designated as BPEI-CDs. The solid catalyst was characterized by various techniques including X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR), atomic force microscopy (AFM), high resolution transmission electron microscopy (HRTEM). The obtained BPEI-CDs are spherical graphite nanocrystals (averaging 5–10 nm). It was found that it could be used as heterogeneous catalyst for Knoevenagel condensation of aromatic aldehydes with malononitrile at 60 °C in ethanol. The Knoevenagel aromatic products were obtained with a moderate to excellent conversion within 2 h. The BPEI-CDs as catalyst was easily isolated from the reaction mixtures by simple filtration and reused for three times without significant loss of catalytic activity. There was also no contribution from the leached active species and conversion was only being possible in the presence of the prepared modified carbon dots.

在这项研究中，用柠檬酸（CA）与支链聚乙烯亚胺（BPEI）在温度（200°C）下碳化，制备了涂有稀释聚乙烯亚胺的碳点，称为BPEI-CD。固体催化剂通过各种技术进行表征，包括X射线粉末衍射（XRD），傅立叶变换红外（FT-IR），原子力显微镜（AFM），高分辨率透射电子显微镜（HRTEM）。获得的BPEI-CD是球形石墨纳米晶体（平均5-10 nm）。已发现它可以用作芳香醛与丙二腈在60°C乙醇中的Knoevenagel缩合反应的非均相催化剂。获得了Knoevenagel芳香族产品，在2小时内转化率中等至优异。通过简单的过滤，很容易从反应混合物中分离出作为催化剂的BPEI-CDs，并重复使用了3次，而没有明显的催化活性损失。浸出的活性物质也没有贡献，并且仅在制备的改性碳点存在下才可能进行转化。