Marco Lombardo

In the past century, significant advancements in synthetic chemistry undeniably contributed to the wellness of mankind, from the development of new drugs to the design of materials for energy production and storage. However, this technological progress has also brought forth significant challenges, emphasizing the urgent need to rethink chemistry for more environmentally friendly approaches. In this Review a critical and comprehensive analysis of the sustainability in the preparation of commonly used photocatalysts is performed, by employing mass‐based metrics. Additionally, a comparative evaluation is made between some selected photocatalytic protocols and traditional reactions not relying on light. The objective is to quantitatively evaluate claims of sustainability and greenness commonly associated with photocatalysis, by exploring the real impact of photocatalytic procedures on waste generation. This quantitative approach provides insights into the broader concept of sustainable processes, challenging assumptions and encouraging a more rigorous evaluation of green claims in catalysis. Furthermore, the toxicity of the involved species and the availability of the required chemical elements is commented on to provide a global perspective on the sustainability of the analyzed transformations. The results shed light on the true environmental footprint of photocatalysis and reveal that the notion of green chemistry can sometimes be overstated.