Xie Shuailei, Liu Ruoyang, Liu Nengyi, Xu Hetao, Chen Xiong, Wang Xinchen, Jiang Donglin
Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Binhai NewCity, Fuzhou, 350207, China.
Department of Chemistry, Faculty of Science, National University of Singapore, 3 Science Drive 3, Singapore, 117543, Singapore.
Angew Chem Int Ed Engl. 2025 Jan 21;64(4):e202416771. doi: 10.1002/anie.202416771. Epub 2024 Nov 19.
Covalent organic frameworks with unique π architectures and pores could be developed as photocatalysts for transformations. However, they usually form π-stacking layers, so that only surface layers function in photocatalysis. Here we report a strategy for developing vertically expanded frameworks to expose originally inaccessible active sites hidden in layers to catalysis. We designed covalently linked two-dimensional cobalt(II) porphyrin layers and explored coordination bonds to connect the cobalt(II) porphyrin layers with bidentate ligands via a three-component one-pot polymerization. The resultant frameworks expand the interlayer space greatly, where both the up and down faces of each cobalt(II) porphyrin layer are exposed to reactants. Unexpectedly, the vertically expanded frameworks increase skeleton oxidation potentials, decrease exciton dissociation energy, improve pore hydrophilicity and affinity to water, and facilitate water delivery. Remarkably, these positive effects work collectively in the photocatalysis of water oxidation into oxygen, with an oxygen production rate of 1155 μmol g h, a quantum efficiency of 1.24 % at 450 nm, and a turnover frequency of 1.39 h, which is even 5.1-fold as high as that of the π-stacked frameworks and ranks them the most effective photocatalysts. This strategy offers a new platform for designing layer frameworks to build various catalytic systems for chemical transformations.
具有独特π结构和孔隙的共价有机框架可被开发用作转化反应的光催化剂。然而，它们通常会形成π堆积层，使得只有表面层在光催化中发挥作用。在此，我们报道了一种开发垂直扩展框架的策略，以将原本隐藏在层内无法触及的活性位点暴露于催化反应中。我们设计了共价连接的二维钴（II）卟啉层，并通过三组分一锅法聚合探索了配位键，以将钴（II）卟啉层与双齿配体连接起来。所得框架极大地扩展了层间空间，其中每个钴（II）卟啉层的上表面和下表面都暴露于反应物中。出乎意料的是，垂直扩展框架提高了骨架氧化电位，降低了激子解离能，改善了孔隙亲水性和对水的亲和力，并促进了水的输送。值得注意的是，这些积极效应在水氧化成氧气的光催化反应中协同作用，产氧速率为1155 μmol g⁻¹ h⁻¹，在450 nm处的量子效率为1.24%，周转频率为1.39 h⁻¹，甚至是π堆积框架的5.1倍，使其成为最有效的光催化剂。该策略为设计层状框架以构建用于化学转化的各种催化体系提供了一个新平台。
