Chemical modifications of Polyheptazine-imides : carbon-nitride-based semiconductors with improved structure and electronic properties for full photochemical water splitting and novel photocatalytic reactions

在半导体基光催化剂上将水直接分解为H2和O2是实现太阳能可持续利用的理想方法。将水分解光催化与有机转化相结合，将应用范围从燃料生产扩展到有机合成，在不消耗化石资源的情况下提供还原或氧化当量。近年来，由于无金属、低成本、稳定和可持续的人工光合作用特性，具有半导体、PI共轭电子特性的石墨化碳氮化物聚合物引起了人们的强烈研究兴趣。这一效应是由这项联合提案的两位贡献者发现的。尽管水的半裂解反应已经取得了很大的进展，但直接裂解水按化学计量释放出H2和O2的研究还很少。这主要受到放出O2的大激活势垒和过电势不足的仍不理想的半导体能带结构的限制。为了解决上述问题，实现石墨化碳氮化物的整体水分离，从热力学和动力学两个方面进行了优化。为了实现这一目标，提出了一个由中国部分和德国部分组成的联合项目，其中中国小组(Wang)专注于光催化反应的动力学控制以促进气体释放，德国小组之一(Antonietti)专注于热力学问题以促进水的分解。此外，热力学和动力学优化的催化剂还将应用于先进的有机光催化，这将由在该领域拥有广泛专业知识的第二个德国小组(König)执行。理想的互补专业知识将允许改进整体水分解以利用石墨化氮化碳光催化剂生产氢燃料，并利用所开发的光催化氧化还原有机合成与水分解反应相结合的附加值。

The direct splitting of water into H2 and O2 on semiconductor-based photocatalysts is an ideal methodology for the sustainable utilization of solar energy. Coupling water splitting photocatalysis with organic transformations expands applications beyond fuel generation to organic synthesis providing reduction or oxidation equivalents without consumption of fossil resources. Recently, the class of graphitic carbon nitride polymers with their semiconductive, Pi-conjugated electronic features has attracted intense research interests, due to its metal-free, low-cost, stable, and sustainable properties for artificial photosynthesis. This effect was discovered by two of the contributors of this joint proposal. Although significant progress on water half-splitting reactions has been made ever since, the direct water splitting releasing H2 and O2 stoichiometrically has however been rarely realized. This is mainly limited by the large activation barrier to evolve O2 and a still non-optimal semiconductor band structure with insufficient overpotentials. To address the above issues achieving overall water splitting on graphitic carbon nitride, optimizations on both thermodynamic and kinetic aspects are addressed. To achieve this goal, a joint project composed by a Chinese part and a German part is proposed, in which the Chinese group (Wang) focuses on the kinetic control of photocatalytic reactions to facilitate gas release, and one of the German groups (Antonietti) majors in the thermodynamic issues to facilitate water splitting. The thermodynamically and kinetically optimized catalysts are in addition applied to advanced organic photocatalysis, which will be performed by the second German group (König) having a broad expertise in this area. The ideal complementary expertise will allow to improving the overall water splitting to produce hydrogen fuel by graphitic carbon nitride photocatalysts and utilize the added-value of the developed catalysts for photoredox organic synthesis coupled with the water splitting reaction.