CO ₂ Reduction to Methanol in the Liquid Phase: A Review

Excessive carbon dioxide (CO2 ) emissions have been subject to extensive attention globally, since an enhanced greenhouse effect (global warming) owing to a high CO2 concentration in the atmosphere could lead to severe climate change. The use of solar energy and other renewable energy to produce low-cost hydrogen, which is used to reduce CO2 to produce bulk chemicals such as methanol, is a sustainable strategy for reducing carbon dioxide emissions and carbon resources. CO2 conversion into methanol is exothermic, so that low temperature and high pressure are favorable for methanol formation. CO2 is usually captured and recovered in the liquid phase. Herein, the emerging technologies for the hydrogenation of CO2 to methanol in the condensed phase are reviewed. The development of homogeneous and heterogeneous catalysts for this important hydrogenation reaction is summarized. Finally, mechanistic insight on CO2 's conversion into methanol over different catalysts is discussed by taking the available reaction pathways into account.