In this work, a series of cerium phosphate catalysts with different cerium phosphate molar ratios have been synthesized. The prepared catalysts were characterized by means of FTIR, DTA, TGA, XRD, N₂ adsorption–desorption and SEM. Also, the acidic centers of the prepared catalysts were abundantly studied and characterized in terms of type and strength using different techniques. The characterization tools used explained the variety of acidic centers in terms of type and strength due to the variation of cerium to phosphate molar ratio. Its worthy to mentioned that the highly acidic performance of the prepared catalysts was successfully applied in the synthesis of tetrahydrocarbazoles derivatives via Borsche–Drechsel cyclization reaction. The catalysts showed great catalytic activity in the selected reaction as high product yields were obtained using a very small amount of the catalysts under mild reaction conditions. The % yield and the reaction mechanism proves the role played by Brønsted acid sites of the catalyst in indorsing the reaction. The results also demonstrated a high ability of the catalysts to be reused ten times without a significant decrease in the catalytic activity. The synthesized tetrahydrocarbazole derivatives via heterogenous acid-catalyzed Borsche–Drechsel cyclization reaction can be considered as highly efficient and eco-friendly strategy towards many other carbazoles and open a new era in green chemistry as well.

在这项工作中，合成了一系列不同磷酸铈摩尔比的磷酸铈催化剂。通过FTIR、DTA、TGA、XRD、N ₂对制备的催化剂进行表征吸附-解吸和扫描电镜。此外，使用不同技术对制备的催化剂的酸性中心进行了大量研究，并在类型和强度方面进行了表征。由于铈与磷酸盐摩尔比的变化，所使用的表征工具在类型和强度方面解释了酸性中心的多样性。值得一提的是，所制备催化剂的强酸性性能已成功应用于 Borsche-Drechsel 环化反应合成四氢咔唑衍生物。由于在温和的反应条件下使用非常少量的催化剂可以获得高产物收率，因此催化剂在所选反应中显示出很大的催化活性。% 收率和反应机理证明了催化剂的布朗斯台德酸位在反应中起到的作用。结果还表明催化剂具有很高的重复使用能力，可重复使用 10 次，而催化活性没有显着降低。通过多相酸催化的 Borsche-Drechsel 环化反应合成的四氢咔唑衍生物可以被认为是对许多其他咔唑的高效和环保策略，也开启了绿色化学的新时代。