Methane hydrate and shale gas are predicted to have substantial reserves, far beyond the sum of other fossil fuels. Using methane instead of crude oil as a building block is, thus, a very attractive strategy for synthesizing valuable chemicals. Because methane is so inert, its direct conversion needs a high activation energy and typically requires harsh reaction conditions or strong oxidants. Photocatalysis, which employs photons operated under very mild conditions, is a promising technology to reduce the thermodynamic barrier in direct methane conversion and to avoid the common issues of overoxidation and catalyst deactivation. In this Review, we cover the development of photocatalysts and co-catalysts, including the use of inorganic materials and polymeric semiconductors, and explain how the use of batch or flow reaction systems affects the reaction kinetics and product selectivity. We also discuss efforts to understand the underlying reaction mechanisms from both a photophysical and a chemical perspective. Finally, we present our view of the challenges facing this field and suggest potential solutions.

预计甲烷水合物和页岩气的储量将远远超过其他化石燃料的总和。因此，使用甲烷代替原油作为合成原料是一种非常有吸引力的合成有价值化学品的策略。由于甲烷非常惰性，其直接转化需要很高的活化能，通常需要苛刻的反应条件或强氧化剂。光催化在非常温和的条件下使用光子，是一种很有前途的技术，可以减少直接甲烷转化中的热力学障碍，避免常见的过氧化和催化剂失活问题。在这篇评论中，我们介绍了光催化剂和助催化剂的发展，包括无机材料和聚合物半导体的使用，并解释间歇或流动反应系统的使用如何影响反应动力学和产物选择性。我们还讨论了从光物理和化学角度理解潜在反应机制的努力。最后，我们提出了我们对该领域面临的挑战的看法，并提出了潜在的解决方案。