LAUSR

In this study, an effective route is presented for the preparation of boron–nitrogen (BN) codoped carbon nanospheres using the reaction of urea, boric acid, and glucose (as carbon, boron, and nitrogen sources), followed by the surface modification with ascorbic acid and immobilization of Zr(IV) and Ni(II) (BN‐CNS/Zr(IV), Ni(II)) through mild conditions. In addition to B and N elements, which have catalytic roles, the immobilization of Zr(IV) and Ni(II) on the BN‐CNS surfaces created the special bifunctional acid–base catalyst. The prepared catalyst was identified by various characterization techniques, and the efficiency of the catalyst for the synthesis of benzo[g]pyrimido[4,5‐b]quinolinetetraon derivatives was explored in water media at 80°C. High to excellent yield of products, easy recovery of the catalyst, and green reaction conditions are some of the merits of the presented method.