Cheng Yuan-Zhe, Yang Dong-Hui, Ji Wenyan, Hao Peng-Yuan, Ma Pengtao, Wang Jingping, Niu Jingyang, Ding Xuesong, Zhang Lizhi, Han Bao-Hang
CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
J Am Chem Soc. 2024 Aug 21;146(33):22959-22969. doi: 10.1021/jacs.4c01836. Epub 2024 Aug 6.
The vinylene-linked covalent organic frameworks (viCOFs) have been generally synthesized in the presence of homogeneous catalysts such as KOH or trifluoroacetic acid. However, highly ordered viCOFs cannot always be obtained due to the uncommitted growth of viCOF layers in the homogeneous system with ubiquitous catalysts. Here, we propose a scalable protocol to restrict the growth of viCOFs along the two-dimensional (2D) plane by introducing a heterogeneous catalyst, polyoxometalates (POMs). With the unique Brønsted alkalinity and catalytic surface, POMs induce the growth of 2D viCOF layers along the surface of the catalytic substrate and restrain the generation of out-of-plane branches. Based on this protocol, six typical 2D viCOFs with high crystallinity and porosity were synthesized within a shorter reaction time as compared with the reported works using the common homogeneous catalysts for viCOF synthesis. On the basis of the density functional theory calculations and experimental results, a bottom intercalation growth pattern of viCOFs was revealed during the heterogeneous reaction. The unique growth pattern greatly promotes the orderly assembly of monomers, thus shortening the reaction time and improving the crystallinity of viCOFs. Furthermore, this heterogeneous catalysis strategy is suitable for the gram-scale preparation of 2D viCOFs. These results provide a novel avenue for the synthesis of high-quality viCOFs and may bring new insights into the synthetic methodology of COFs.
亚乙烯基连接的共价有机框架（viCOFs）通常是在氢氧化钾或三氟乙酸等均相催化剂存在的情况下合成的。然而，由于在使用无处不在的催化剂的均相体系中viCOF层的无规生长，往往无法获得高度有序的viCOFs。在此，我们提出了一种可扩展的方法，通过引入多金属氧酸盐（POMs）这种非均相催化剂来限制viCOFs沿二维（2D）平面的生长。凭借其独特的布朗斯台德碱性和催化表面，POMs诱导二维viCOF层沿着催化底物的表面生长，并抑制平面外分支的产生。基于此方法，与使用常见均相催化剂合成viCOF的已报道工作相比，在更短的反应时间内合成了六种具有高结晶度和孔隙率的典型二维viCOFs。基于密度泛函理论计算和实验结果，揭示了非均相反应过程中viCOFs的底部插层生长模式。这种独特的生长模式极大地促进了单体的有序组装，从而缩短了反应时间并提高了viCOFs的结晶度。此外，这种非均相催化策略适用于二维viCOFs的克级制备。这些结果为高质量viCOFs的合成提供了一条新途径，并可能为COFs的合成方法带来新的见解。
