Synthesis of Well-Ordered COF Monolayers: Surface Growth of Nanocrystalline Precursors versus Direct On-Surface Polycondensation
Synthesis of Well-Ordered COF Monolayers: Surface Growth of Nanocrystalline Precursors versus Direct On-Surface Polycondensation
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DOI：
10.1021/nn2032616
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发表时间：
2011-12-01
期刊：
影响因子：
17.1
通讯作者：
Lackinger, Markus
中科院分区：
文献类型：
--
作者：
Dienstmaier, Juergen F.;Gigler, Alexander M.;Lackinger, Markus
提出了两种不同的直接合成方法来制备共价有机骨架(COF)在惰性、催化非活性的石墨表面上的长程有序单分子膜。聚合反应采用硼酸缩合(脱水)。在第一种方法中，单体仅通过热处理预聚成纳米晶前驱体COF。然后将前驱体滴铸到石墨衬底上，并用扫描隧道显微镜(STM)对其进行表征。虽然在前体中，单体已经共价连接到最终的COF结构中，但得到的结构域尺寸仍然相当小。我们发现，在可逆反应条件下的热处理促进了表面的成熟，并伴随着微区尺寸的显着增加。虽然第一种方法允许研究聚合的不同阶段，但直接聚合是可取的，也就是说，不需要预先的反应步骤。我们证明，即使对于相对较小的二硼酸单体，也可以直接热激活聚合成扩展的COF单分子层。
Two different straightforward synthetic approaches are presented to fabricate long-range-ordered monolayers of a covalent organic framework (COF) on an inert, catalytically inactive graphite surface. Boronic acid condensation (dehydration) is employed as the polymerization reaction. In the first approach, the monomer is prepolymerized by a mere thermal treatment into nanocrystalline precursor COFs. The precursors are then deposited by drop-casting onto a graphite substrate and characterized by scanning tunneling microscopy (STM). While in the precursors monomers are already covalently interlinked into the final COF structure, the resulting domain size is still rather small. We show that a thermal treatment under reversible reaction conditions facilitates on-surface ripening associated with a striking increase of the domain size. Although this first approach allows studying different stages of the polymerization, the direct polymerization, that is, without the necessity of preceding reaction steps, is desirable. We demonstrate that even for a comparatively small diboronic acid monomer a direct thermally activated polymerization into extended COF monolayers is achievable.