Acid–Base\nBifunctional Catalysis of the Lewis\nAcidic Isolated Co(OH)<sub>2</sub> and Basic N Anion Generated from\nCeO<sub>2</sub> and 2‑Cyanopyridine

Acid–base bifunctional catalysts,\nwhich have both\nacid and\nbase sites that are arranged at an appropriate distance, are one of\nthe effective catalyst categories and have been extensively studied\nas a simple and effective method for designing heterogeneous and homogeneous\ncatalysts in both the laboratories and industry. Recently, we found\nthat a heterogeneous–homogeneous hybrid strong base site of\nN<sup>–</sup> was constructed only by mixing 2-cyanopyridine\nand CeO<sub>2</sub> in the solution, where the N<sup>–</sup> site was formed by the covalent bonding between the lattice O atom\nof CeO<sub>2</sub> and the C atom of the CN group in 2-cyanopyridine.\nHerein, an effective acid–base bifunctional catalyst with proximal\nsites of the heterogeneous–homogeneous hybrid base site and\nmetal species-derived Lewis acid site is presented. The introduction\nof Co species into CeO<sub>2</sub> forms isolated Co(OH)<sub>2</sub> on CeO<sub>2</sub>, and further introduction of 2-cyanopyridine\ngenerates the heterogeneous–homogeneous hybrid base site of\nN<sup>–</sup> near the Co(OH)<sub>2</sub> without the interference\nof these sites. The acid–base bifunctional sites work cooperatively\nto provide about 10-fold higher activity to the hydromethoxylation\nof acrylonitrile than the heterogeneous–homogeneous hybrid\nbase site alone. Catalyst characterizations such as XRD, TEM, UV–vis,\nNO adsorption, XPS, Raman, XAS, NH<sub>3</sub>-TPD and in situ XPS,\nDFT calculations, and kinetic studies show that acrylonitrile and\nmethanol are activated by the Lewis acidic Co(OH)<sub>2</sub> and\nthe hybrid base site, respectively, and the cooperative work results\nin the large rate enhancement.