Solar-Driven CO2 Conversion: A Review of Long-Chain Products

The solar-driven conversion of CO2 into long-chain (C3+) products offers a sustainable pathway to mitigate climate change, produce carbon-neutral fuels and value-added chemicals. Over the past few decades, significant advances have been achieved in CO2 photoreduction; however, most systems still favor C1 products (CO, CH4) or C2 intermediates. However, the synthesis of C3+ products poses a formidable challenge due to the complex multi-electron transfer steps required for C–C bond formation. This review provides a concise overview of recent progress in solar-driven photocatalytic and photothermal CO2 reduction, with a specific focus on the formation of C3+ products. The fundamental principles are discussed, including the critical role of C–C coupling mechanisms and the stepwise reaction pathways for C3+ products. It highlights how the extended carbon chain length significantly increases the complexity and reduces selectivity, with the suppression of side reactions being a primary research objective. Key catalytic strategies, such as the use of copper-based materials, are examined for their unique ability to facilitate these demanding transformations. Finally, the major challenges are outlined, and a future outlook for this field is provided, with an emphasis on the need for advanced catalyst design and in situ characterization to unlock the potential of solar fuels.