Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany.
Faraday Discuss. 2017 Sep 8;201:247-264. doi: 10.1039/c7fd00051k.
Organic solids such as covalent organic frameworks (COFs), porous polymers and carbon nitrides have garnered attention as a new generation of photocatalysts that offer tunability of their optoelectronic properties both at the molecular level and at the nanoscale. Owing to their inherent porosity and well-ordered nanoscale architectures, COFs are an especially attractive platform for the rational design of new photocatalysts for light-induced hydrogen evolution. In this report, our previous design strategy of altering the nitrogen content in an azine-linked COF platform to tune photocatalytic hydrogen evolution is extended to a pyridine-based photocatalytically active framework, where nitrogen substitution in the peripheral aryl rings reverses the polarity compared to the previously studied materials. We demonstrate how simple changes at the molecular level translate into significant differences in atomic-scale structure, nanoscale morphology and optoelectronic properties, which greatly affect the photocatalytic hydrogen evolution efficiency. In an effort to understand the complex interplay of such factors, we carve out the conformational flexibility of the PTP-COF precursor and the vertical radical anion stabilization energy as important descriptors to understand the performance of the COF photocatalysts.
有机固体，如共价有机框架（COFs）、多孔聚合物和碳氮化物，作为新一代光催化剂引起了人们的关注，它们在分子水平和纳米尺度上都具有可调谐的光电特性。由于其固有多孔性和有序的纳米级结构，COFs 是合理设计用于光诱导析氢的新型光催化剂的一个特别有吸引力的平台。在本报告中，我们之前改变嗪键 COF 平台中氮含量的设计策略被扩展到基于吡啶的光催化活性框架中，其中在芳环的外围取代氮会使极性与之前研究的材料相反。我们展示了分子水平上的简单变化如何转化为原子尺度结构、纳米形貌和光电特性的显著差异，这极大地影响了光催化析氢效率。为了了解这些因素的复杂相互作用，我们将 PTP-COF 前体的构象灵活性和垂直自由基阴离子稳定能作为理解 COF 光催化剂性能的重要描述符。
