Organic–inorganic S-scheme heterojunction photocatalysts: Design, synthesis, applications, and challenges

Since the concept was introduced in 2019, step-scheme (S-scheme) heterojunctions have emerged as an important subclass of heterojunction technology and attracted much attention for solar energy conversion. S-scheme heterojunctions are capable of maximizing redox ability through conferring enhanced photocatalytic performance by addressing the problem of rapid electron–hole recombination. In particular, the organic–inorganic S-scheme heterojunction (OI-SHJ) can integrate atomic long-range ordered inorganic semiconductors with tailored organic materials using diverse organic molecular building blocks and integration methods, offering brilliant prospects for innovation. Here, we review the state-of-the-art progress in OI-SHJ photocatalysts by introducing their charge transfer mechanism, design criteria, preparation approaches, and applications. We also highlight the synergistic role of organic and inorganic materials in S-scheme heterojunctions and what is understood so far about their structure–activity relationship. We conclude by summarizing the existing challenges and emphasizing the current outlook for the future development of OI-SHJ photocatalysts.