Photocatalytic water reduction into hydrogen using solar energy is an ideal way for the storage of renewable energy. Currently, a great number of photocatalysts with high activity and stability have been developed for hydrogen evolution. The use of metal components is commonly indispensable for highly efficient hydrogen evolution, and the catalytic mechanism at the molecular level remains ambiguous for heterogeneous systems. We report here a pyridine-terminated organic small molecular photocatalyst with superior hydrogen-evolution activity under visible-light irradiation in non-acidic aqueous media, with a turnover number of 281 being achieved in 28 h. Combined experimental and theoretical studies suggest that the water reduction occurs via a homolytic elimination of two pyridine-hydrogen radicals generated by multistep light-induced proton-coupled electron transfer processes. The success of this small molecular organic photocatalyst with both structural integration and functional separation for light harvesting and catalysis opens a revolutionary prospect for simple and low-cost solar energy utilization.

利用太阳能光催化将水还原为氢气是存储可再生能源的理想方式。目前，已经开发出大量具有高活性和稳定性的光催化剂用于析氢。金属组分的使用对于高效析氢通常是必不可少的，并且对于非均相系统，分子水平的催化机制仍然不明确。我们在此报道了一种吡啶封端的有机小分子光催化剂，在非酸性水介质中的可见光照射下具有优异的析氢活性，28小时内的周转数达到281。实验和理论相结合的研究表明，水的减少是通过多步光诱导质子耦合电子转移过程产生的两个吡啶氢自由基的均裂消除而发生的。这种具有结构集成和功能分离的小分子有机光催化剂在光捕获和催化方面的成功，为简单、低成本的太阳能利用开辟了革命性的前景。