Bifunctional solid acid photocatalyst TiO2/AC/SO3H with high acid density for pure green photosynthesis of 2-quinoline carboxamide

• High acid density TiO2/AC/SO3H bifunctional solid acid photocatalyst was prepared.
• Pure green photosynthesis of 2-quinoline carboxamide was realized.
• The maximum yield of 2-quinoline carboxamide of 39% was obtained.
• AC is not only the solid acid but also the supporter for TiO2.
• The yield of 2-quinoline carboxamide was correlated with the acid density of catalyst.

Quinoline ramifications possess a wide range of biological activities and potential pharmacological activities. Here, a concept of bifunctional solid acid photocatalyst TiO2/AC/SO3H with high acid density is firstly purposed for efficiently pure green synthesis of 2-quinoline carboxamide under ultraviolet-visible light irradiation. After sulfonation, the acid density of TiO2/AC is markedly larger than that of sole TiO2 or AC, and the maximum yield of 2-quinoline carboxamide of 39% is obtained when the acid density of catalyst reaches 1.55 mmol/g. The new concept of bifunctional catalysis using solid acid and photocatalyst is potential for industrial application and instructive in green organic synthesis reactions which need radical and acid simultaneously.

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