摘要：在此，作者报道了一种具有独特[4 + 2]互穿结构的三维共价有机框架，即COF-308的合成。这种互穿模式不仅没有引起不必要的结构动态变化和表面积的显著下降，反而增强了结构刚性并实现了理想的表面积。通过分辨率为0.95 Å的单晶X射线衍射（SCXRD）分析，揭
本文要点：
在此，作者报道了一种具有独特[4 + 2]互穿结构的三维共价有机框架，即COF-308的合成。这种互穿模式不仅没有引起不必要的结构动态变化和表面积的显著下降，反而增强了结构刚性并实现了理想的表面积。通过分辨率为0.95 Å的单晶X射线衍射（SCXRD）分析，揭示了这种互穿结构。观察到相邻框架中四面体形状的构建单元以“面对面”的方式堆积，这种堆积方式锁定了滑动并扭曲了分子运动。通过原位小角X射线散射技术，结合气体吸附和解吸过程，进一步评估了结构的刚性和永久孔隙率。在整个等温线范围内研究了气体的分布，揭示了COF-308内部孔道的各向异性。这种各向异性非常适合气体存储和分离，其特性源于这种新的互穿模式，其中构建单元的“面对面”堆积被证明是关键的控制因素。Figure 1. A subtle change in the packing mode of building blocks leads to the precise control of interpenetration in the COF.
Figure 2. Fixation of framework dynamics in COF-308 single crystals. (A) Schematic illustration for the synthesis of COF-308 single crystals and the corresponding optical image. Scale bar: 100 μm. (B) Comparison of “unlocked” and “locking” frameworks with “edge-to-edge” and “face-to-face” packing modes of TAM building blocks in COF-300 and COF-308, respectively. C, N, O, and H atoms are labeled gray, blue, red, and purple, respectively.
Figure 3. Analysis of [4 + 2] interpenetration in COF-308. (A) The overall structure is dissected into two sets of frameworks, Net I with 4-fold interpenetration marked in blue and Net II with 2-fold, in red. These nets are capable of structure dynamics as separate frameworks; however, they keep the overall structure rigidity when integrated. (B) Interpenetration mode is viewed from a- and b-axes, respectively. Unit cells are displayed in gray. The key rotation axis and screw axis are also displayed.
Figure 4. Gas adsorption crystallography on COF-308. (A) N2 isotherm of COF-308 and COF-300 measured at 77 K, in black and gray dots, respectively. (B) SAXS profiles were measured along the entire adsorption process with 10 selected gas pressure points, corresponding to the points on the isotherm displayed in the same color. Si is used as an internal standard. (C) N2 distribution is presented in 2D electron density maps along the [010] direction at these points. (D) Detailed analysis of the channels in COF-308 viewed along the [010] direction, where the aperture sizes of three types of channels are compared. (E) The position, pore size and, chemical environment of the 4 types of pores in CIII, viewed along [010] direction. The blue arrows outline the orientation of −OMe groups.
来源：华算科技