Single‐Pore versus Dual‐Pore Bipyridine‐Based Covalent–Organic Frameworks: An Insight into the Heterogeneous Catalytic Activity for Selective CH Functionalization
Harsh Vardhan, Abdullah M. Al‐Enizi, Ayman Nafady, Yanxiong Pan, Zhongyu Yang, Humberto R. Gutiérrez, Xiaolong Han, Shengqian Ma
Abstract
Abstract Exponential growth in the field of covalent–organic frameworks (COFs) is emanating from the direct correlation between designing principles and desired properties. The comparison of catalytic activity between single‐pore and dual‐pore COFs is of importance to establish structure–function relationship. Herein, the synthesis of imine‐linked dual‐pore [(BPyDC)] x % ‐ETTA COFs ( x = 0%, 25%, 50%, 75%, 100%) with controllable bipyridine content is fulfilled by three‐component condensation of 4,4′,4″,4′″‐(ethene‐1,1,2,2‐tetrayl)tetraaniline (ETTA), 4,4′‐biphenyldialdehyde, and 2,2′‐bipyridyl‐5,5′‐dialdehyde in different stoichiometric ratio. The strong coordination of bipyridine moieties of [(BPyDC)] x % ‐ETTA COFs with palladium imparts efficient catalytic active sites for selective functionalization of sp 2 CH bond to CX (X = Br, Cl) or CO bonds in good yield. To broaden the scope of regioselective CH functionalization, a wide range of electronically and sterically substituted substrates under optimized catalytic condition are investigated. A comparison of the catalytic activity of palladium decorated dual‐pore frameworks with single‐pore imine‐linked Pd(II) @ Py‐2,2′‐BPyDC framework is undertaken. The finding of this work provides a sporadic example of chelation‐assisted CH functionalization and disclosed an in‐depth comparison of the relationship between superior catalytic activity and core properties of rationally designed imine linked frameworks.