Department of Chemistry, University of Kalyani, Kalyani, Nadia, 741235, W.B., India.
Department of Chemistry, Indian Institute of Technology (IIT) Madras, Chennai 600036, India.
Org Biomol Chem. 2022 Feb 23;20(8):1707-1722. doi: 10.1039/d1ob01938d.
A simple covalent organic framework (COF) bearing β-ketoenamine units as a potential heterogeneous ligand for Zn-catalyzed fixation and transformation of CO into value-added chemicals is reported. Catalytic investigations convincingly demonstrated that the Zn-functionalized covalent organic framework (Zn@TpTta) exhibits perfect catalytic activity in the fixation of CO for diverse epoxides with various substituents under sustainable conditions. A variety of terminal epoxides and slightly more complicated disubstituted epoxides were transformed into the corresponding cyclic carbonates with satisfactory to excellent yields (, 69 to 99% yield) upon exposure to CO (1 atm) under solvent-free conditions (sustainable approach). On the other hand, this Zn-loaded covalent organic framework also displayed excellent performance in facilitating atmospheric cyclizative CO capture, which led to the formation of diverse cyclic carbamates (, 61 to 94% yield) from unsaturated amine systems using -iodosuccinimide (NIS) as an iodinating agent and PEG-400 as a biodegradable and green polymeric solvent under base-free conditions (sustainable approach). The newly synthesized COF-based catalyst, namely, Zn@TpTta, has been completely characterized by SEM (scanning electron microscopy), EDX (energy dispersive X-ray analysis), HRTEM (high-resolution transmission electron microscopy), BET (Brunauer-Emmett-Teller), PXRD (powder X-ray diffraction), XPS (X-ray photoelectron spectroscopy), ICP (inductively coupled plasma), . More intriguingly, the catalytic system could be recycled over five times without a noticeable loss of catalytic performance for both reactions. This study opens an avenue for the Zn(II) embedded COF as a promising platform for regulating regioselectivity.
报道了一种含有β-酮亚胺单元的简单共价有机框架（COF），它可以作为一种潜在的非均相配体，用于 Zn 催化的 CO 固定和转化为有价值的化学品。催化研究令人信服地表明，Zn 功能化的共价有机框架（Zn@TpTta）在可持续条件下，对具有各种取代基的各种环氧化物的 CO 固定表现出完美的催化活性。在无溶剂条件下（可持续方法），当暴露于 CO（1 atm）时，多种末端环氧化物和稍微复杂的二取代环氧化物转化为相应的环状碳酸酯，产率令人满意至优秀（，69 至 99%的产率）。另一方面，这种负载 Zn 的共价有机框架在促进大气环合 CO 捕获方面也表现出优异的性能，它使用 N-碘代琥珀酰亚胺（NIS）作为碘代试剂和 PEG-400 作为可生物降解和绿色聚合物溶剂，从不饱和胺体系中形成了多种环状氨基甲酸酯（，61 至 94%的产率）在无碱条件下（可持续方法）。新合成的基于 COF 的催化剂，即 Zn@TpTta，已通过 SEM（扫描电子显微镜）、EDX（能量色散 X 射线分析）、HRTEM（高分辨率透射电子显微镜）、BET（Brunauer-Emmett-Teller）、PXRD（粉末 X 射线衍射）、XPS（X 射线光电子能谱）、ICP（电感耦合等离子体）和. 更有趣的是，该催化体系在两种反应中可回收五次以上，而催化性能没有明显损失。这项研究为 Zn(II) 嵌入 COF 作为调节区域选择性的有前途的平台开辟了道路。
