The traditional vacuum activation of covalent organic framework (COF) materials typically erodes the materials’ crystallinity significantly and then reduces the surface area of isolated materials. Developing new methods for synthesizing robust COFs which could survive the duration of the vacuum activation process is of great practical significance. In this work, a robust imine-linked 2D COF TAPB-TA was creatively constructed in supercritical CO₂ (ScCO₂) with γ-valerolactone (GVL) as a cosolvent instead of previously widely reported reaction conditions. Upon vacuum activation, the as-prepared COF (denoted as Sc-COF) via this green synthesis could still possess a high surface area, while preventing the pores from undesirable collapse and the loss of material quality could be avoided successfully. Further, Sc-COF showed excellent stability toward solvent immersion–reactivation cycles. Furthermore, this method is universal and can be facilely extended to the synthesis of other imine-linked 2D COFs and is expected to be transferable to a broader range of customized COFs. Theoretic calculations imply that ScCO₂ serves to attenuate the COF–COF interactions during the activation process preventing the collapse of the structure. It decreases the viscosity of the solution as compared to pure GVL, enabling fast diffusion kinetics of monomers to the reactive sites. Moreover, thanks to the low dielectric constant, usage of the ScCO₂ solvent diminishes the energy barriers of imine bond formation, thus facilitating ordered COF growth. These insights have important implications for studying and understanding how more robust 2D COFs could form and thus greatly expand their practical applications.

中文翻译：

---

超临界二氧化碳中稳健亚胺连接的二维共价有机骨架的绿色合成

共价有机骨架 (COF) 材料的传统真空活化通常会显着侵蚀材料的结晶度，然后降低孤立材料的表面积。开发能够在真空活化过程中存活下来的稳健 COF 的合成新方法具有重要的实际意义。在这项工作中，在超临界 CO ₂ (ScCO ₂) 以 γ-戊内酯 (GVL) 作为共溶剂，而不是以前广泛报道的反应条件。在真空活化后，通过这种绿色合成制备的 COF（表示为 Sc-COF）仍然可以具有高表面积，同时防止孔隙发生意外塌陷，并且可以成功避免材料质量的损失。此外，Sc-COF 对溶剂浸泡-再活化循环表现出优异的稳定性。此外，该方法具有通用性，可以轻松扩展到其他亚胺连接的二维 COF 的合成，并有望转移到更广泛的定制 COF 中。理论计算表明 ScCO ₂用于在激活过程中减弱 COF-COF 相互作用，防止结构坍塌。与纯 GVL 相比，它降低了溶液的粘度，使单体能够快速扩散到反应部位。此外，由于介电常数低，ScCO ₂溶剂的使用降低了亚胺键形成的能垒，从而促进有序的COF生长。这些见解对于研究和理解如何形成更稳健的 2D COF 具有重要意义，从而极大地扩展了它们的实际应用。