Deutsches Museum, Museumsinsel 1, 80538 Munich, Germany.
ACS Nano. 2011 Dec 27;5(12):9737-45. doi: 10.1021/nn2032616. Epub 2011 Nov 10.
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.
提出了两种不同的简单合成方法，用于在惰性、无催化活性的石墨表面上制造共价有机框架（COF）的长程有序单层。硼酸缩合（脱水）被用作聚合反应。在第一种方法中，单体通过简单的热处理预聚合成长程有序的 COF 纳米晶前体。然后通过滴铸将前体沉积在石墨基底上，并通过扫描隧道显微镜（STM）进行表征。虽然在预聚物中单体已经共价连接成最终的 COF 结构，但所得的畴尺寸仍然相当小。我们表明，在可逆反应条件下进行热处理有助于表面熟化，同时畴尺寸显著增加。尽管这种第一种方法允许研究聚合的不同阶段，但直接聚合，即不需要前面的反应步骤，是理想的。我们证明，即使对于相对较小的二硼酸单体，也可以通过直接热激活聚合来实现扩展的 COF 单层。
