Microkinetic insights into the role of catalyst and water activity on the nucleation, growth, and dissolution during COF-5 synthesis
Microkinetic insights into the role of catalyst and water activity on the nucleation, growth, and dissolution during COF-5 synthesis
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COF-5 合成过程中催化剂和水活性对成核、生长和溶解作用的微动力学见解
DOI：
10.1039/d2nr06685h
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发表时间：
2023
期刊：
影响因子：
6.7
通讯作者：
Singh, Meenesh R.
中科院分区：
文献类型：
--
作者：
Dighe, Anish V.;Bhawnani, Rajan R.;Podupu, Prem K.R.;Dandu, Naveen K.;Ngo, Anh T.;Chaudhuri, Santanu;Singh, Meenesh R.
合成共价有机骨架(COF)的化学途径涉及一系列复杂的反应序列，这些反应序列覆盖着涟漪般的能量格局，而现有的理论无法充分描述这一点。即使发展了最先进的实验和计算工具，识别COF成核和生长的主要机制仍然是难以捉摸的。除了经验之外，关于催化剂的组成和水的活性如何影响反应路径的动力学，我们知之甚少。在这里，我们首次使用了时间分辨的原位傅里叶变换红外光谱(FT-IR)，并结合了一个包含∼1000万个反应和超过20000个 000个物种的六参数微观动力学模型。该综合方法阐明了以前未知的催化剂PKA对COF产率的影响以及水对生长速度和粒度分布的影响。随着催化剂pKa的降低，CoF的结晶率增加，而水的作用则是降低了CoF的生长速度，拓宽了COF的尺寸分布。微观动力学模型再现了实验数据，并定量预测了温度、催化剂和前驱体浓度等合成条件对成核和生长速度的影响。此外，该模型还验证了CoF-5的二级反应机理，并预测了CoF-5晶体经典和非经典生长的活化势垒。建立的微观动力学模型可推广到不同的COF和其他多组分体系。
The chemical pathway for synthesizing covalent organic frameworks (COFs) involves a complex medley of reaction sequences over a rippling energy landscape that cannot be adequately described using existing theories. Even with the development of state-of-the-art experimental and computational tools, identifying primary mechanisms of nucleation and growth of COFs remains elusive. Other than empirically, little is known about how the catalyst composition and water activity affect the kinetics of the reaction pathway. Here, for the first time, we employ time-resolved in situ Fourier transform infrared spectroscopy (FT-IR) coupled with a six-parameter microkinetic model consisting of ∼10 million reactions and over 20 000 species. The integrated approach elucidates previously unrecognized roles of catalyst pKa on COF yield and water on growth rate and size distribution. COF crystalline yield increases with decreasing pKa of the catalysts, whereas the effect of water is to reduce the growth rate of COF and broaden the size distribution. The microkinetic model reproduces the experimental data and quantitatively predicts the role of synthesis conditions such as temperature, catalyst, and precursor concentration on the nucleation and growth rates. Furthermore, the model also validates the second-order reaction mechanism of COF-5 and predicts the activation barriers for classical and non-classical growth of COF-5 crystals. The microkinetic model developed here is generalizable to different COFs and other multicomponent systems.