Urea-Linked Covalent Organic Frameworks

2D covalent organic frameworks (COFs) with flexible urea linkages have been synthesized by condensation of 1,3,5-triformylphloroglucinol (TFP) with 1,4-phenylenediurea (BDU) or 1,1′-(3,3′-dimethyl-[1,1′-biphenyl]-4,4′-diyl)­diurea (DMBDU). The resulting COF-117 and COF-118 undergo reversible structural dynamics within their layers, in response to inclusion and removal of guest molecules, emanating from urea CN bond rotation and interlayer hydrogen-bonding interactions. These compounds are the first urea-linked COFs, serving to expand the scope of reticular chemistry.通过1,3,5-三甲酰基间苯三酚 (1,3,5-triformylphloroglucinol，TFP) 分别与1,4-苯二脲 (1,4-phenylenediurea，BDU)、1,1′-(3,3′-二甲基-[1,1′-联苯]-4,4′-二基)二脲 (1,1′-(3,3′-dimethyl-[1,1′-biphenyl]-4,4′-diyl)diurea，DMBDU) 发生缩合反应，成功合成出带有柔性脲键连接的二维共价有机框架 (2D covalent organic frameworks，COFs)。所得到的COF-117与COF-118可在层内发生可逆结构动态变化，该变化响应客体分子的吸附与脱附过程，其机制源于脲基C-N键旋转与层间氢键相互作用。此类化合物为首例脲键连接的共价有机框架，有助于拓展网状化学 (reticular chemistry) 的研究范畴。