Covalent organic frameworks writ large Covalent organic framework (COF) materials have been difficult to characterize structurally and to exploit because they tend to form powders or amorphous materials. Ma et al. studied a variety of three-dimensional COFs based on imine linkages (see the Perspective by Navarro). They found that the addition of aniline inhibited nucleation and allowed the growth of crystals large enough for single-crystal x-ray diffraction studies. Evans et al. describe a two-step process in which nanoscale seeds of boronate ester–linked two-dimensional COFs can be grown into micrometer-scale single crystals by using a solvent that suppresses the nucleation of additional nanoparticles. Transient absorption spectroscopy revealed superior charge transport in these crystallites compared with that observed in conventional powders. Science, this issue p. 48, p. 52; see also p. 35 The addition of aniline enables the growth of single crystals of imine-based covalent organic framework materials. The crystallization problem is an outstanding challenge in the chemistry of porous covalent organic frameworks (COFs). Their structural characterization has been limited to modeling and solutions based on powder x-ray or electron diffraction data. Single crystals of COFs amenable to x-ray diffraction characterization have not been reported. Here, we developed a general procedure to grow large single crystals of three-dimensional imine-based COFs (COF-300, hydrated form of COF-300, COF-303, LZU-79, and LZU-111). The high quality of the crystals allowed collection of single-crystal x-ray diffraction data of up to 0.83-angstrom resolution, leading to unambiguous solution and precise anisotropic refinement. Characteristics such as degree of interpenetration, arrangement of water guests, the reversed imine connectivity, linker disorder, and uncommon topology were deciphered with atomic precision—aspects impossible to determine without single crystals.

中文翻译：

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共价有机骨架的单晶 X 射线衍射结构

共价有机骨架写大 共价有机骨架 (COF) 材料难以在结构上表征和开发，因为它们倾向于形成粉末或无定形材料。马等人。研究了基于亚胺键的各种三维 COF（参见 Navarro 的观点）。他们发现加入苯胺会抑制成核，并允许晶体生长足够大以进行单晶 X 射线衍射研究。埃文斯等人。描述了一个两步过程，其中硼酸酯连接的二维 COF 的纳米级种子可以通过使用抑制额外纳米粒子成核的溶剂生长成微米级单晶。与在常规粉末中观察到的相比，瞬态吸收光谱显示这些微晶中的电荷传输更优。科学，这个问题 p。48 页。52; 另见第。35 添加苯胺可以生长亚胺基共价有机骨架材料的单晶。结晶问题是多孔共价有机骨架 (COF) 化学中的一个突出挑战。它们的结构表征仅限于基于粉末 X 射线或电子衍射数据的建模和解决方案。尚未报道可用于 X 射线衍射表征的 COF 单晶。在这里，我们开发了一种通用程序来生长三维亚胺基 COF（COF-300、COF-300、COF-303、LZU-79 和 LZU-111 的水合形式）的大型单晶。高质量的晶体允许收集分辨率高达 0.83 埃的单晶 X 射线衍射数据，导致明确的解决方案和精确的各向异性细化。诸如互穿程度、水客体排列、反向亚胺连接、链接器无序和不常见拓扑结构等特征以原子精度破译——如果没有单晶就无法确定这些方面。