On-surface synthesis of 2D COFs on Cu(111) via the formation of thermodynamically stable organometallic networks as the template
On-surface synthesis of 2D COFs on Cu(111) via the formation of thermodynamically stable organometallic networks as the template
复制标题
通过形成热力学稳定的有机金属网络作为模板，在 Cu(111) 上表面合成二维 COF
DOI：
10.1039/c9cp01843c
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发表时间：
2019
影响因子：
3.3
通讯作者：
Liu Pei-Nian
中科院分区：
文献类型：
--
作者：
Wang Cheng-Xin;Chen Jian-Le;Shu Chen-Hui;Shi Ke-Ji;Liu Pei-Nian
模板定向聚合是一种有效的方法，用于提供规则的二维共价有机框架（COFs），因此模板的规则性对所得到的二维COFs的质量至关重要。对于Cu（111）上的Ullmann反应，芳基碘化物和溴化物在低温下被激活形成有机金属C-Cu-C结构，导致动力学捕获和不规则的有机金属网络。因此，后续退火步骤只能得到不规则的二维COFs。在本文中，4,4 " -二溴-5 ' -（4-氯苯基）-1,1 ':3 ',1 " -terphenyl分子结合了两个Br端和一个Cl端，通过Cu上的C-Br键和C-Cl键的分层活化，证明了C-Cl键和C-Br键的不同反应活性（111）。在室温下，由于C-Br键的激活，形成了锯齿状、扶手状和环状的有机金属链，形成了C-Cu-C结构，而C-Cl保持不变，说明C-Cl键比C-Br更稳定。在433 K下进一步退火，激活了C-Cl键，产生规则的有机金属网络作为热力学产物。以较简单的分子1,3,5-三（4-氯苯）苯为前驱体，在300 K的温度下，在Cu（111）上观察到完整分子的自组装，而没有激活C-Cl键。在433 K退火后，直接形成了类似的热力学稳定的有机金属网络，在510 K进一步退火后，将其作为模板生成规则的二维COFs。
Template-directed polymerization is an effective approach used to afford regular 2D covalent organic frameworks (COFs), thus the regularity of the template is crucial for the quality of the resulting 2D COFs. For the Ullmann reactions on Cu(111), aryl iodides and bromides are activated at low temperature to form organometallic C–Cu–C structures, which lead to kinetic trapping and irregular organometallic networks. Therefore, the subsequent annealing step can only afford irregular 2D COFs. In this manuscript, the molecule 4,4′′-dibromo-5′-(4-chlorophenyl)-1,1′:3′,1′′-terphenyl incorporated two Br terminals and one Cl terminal has been used to demonstrate different reactivities of a C–Cl bond and a C–Br bond via the hierarchical activation of the C–Br bond and the C–Cl bond on Cu(111). At room temperature, zigzag, armchair, and ring-like organometallic chains formed due to the activation of the C–Br bond to generate a C–Cu–C structure while C–Cl remained intact, illustrating that the C–Cl bond is more stable than C–Br. Further annealing at 433 K activated the C–Cl bond to produce regular organometallic networks as the thermodynamic product. Using the simpler molecule 1,3,5-tris(4-chlorophenyl)benzene as the precursor, the self-assembly of the intact molecules was observed on Cu(111) at 300 K without activation of the C–Cl bond. After annealing at 433 K, similar thermodynamically stable organometallic networks formed directly, which were used as a template to generate regular 2D COFs upon further annealing at 510 K.