Cobalt sandwich complex-based covalent organic frameworks for chemical fixation of CO

含钴夹层结构的共价有机框架用于二氧化碳的化学固定

Carbon dioxide as a notorious greenhouse gas triggers severe global warming which is threatening the balance of ecosystem. In this respect, effectively capturing and transforming CO_(2)into value-added chemicals are essential but still challenging tasks. As a kind of emerging crystalline porous material, covalent organic frameworks(COFs) have been demonstrated to be able to adsorb gases and function as catalysts to facilitate chemical transformations. Herein, we report an imine-linked, cobalt sandwich complex-based COF(Co-BD-COF) with high crystallinity and large surface area.Co-BD-COF can efficiently catalyze the transformation of CO_(2)into cyclic carbonates due to abundant metal sites and high porosity. In addition, Co-BD-COF exhibits high catalytic selectivity toward small ethylene oxide derivatives in cycloaddition reaction due to the large steric hindrance around the cobalt complexes rendered by the peripheral phenyl moieties.This new metal sandwich-type building block provides a new strategy for improving catalytic selectivity of COFs.

二氧化碳作为主要的温室气体导致了全球变暖,并威胁着生态系统的平衡.有效捕获二氧化碳并将其转化为增值化学品具有重要的意义,但也充满挑战.作为一种新兴的多孔晶态材料,共价有机框架(COFs)不仅能有效吸附气体,而且可作为化学转化催化剂.本文报道了一种由亚胺连接的含夹层钴配合物的COF(Co-BD-COF), Co-BD-COF表现出较高的结晶度和较大的比表面积. Co-BD-COF还兼具丰富的金属位点和较高的孔隙率,能有效地催化CO_(2)转化为环状碳酸酯.此外,Co-BD-COF在环加成反应中表现出对小体积的环氧乙烷衍生物的高效选择性,这种高效选择性来源于夹层钴配合物周围的苯基部分所形成的空间位阻作用.将金属夹层配合物构筑到COF骨架,为提高COFs的催化选择性提供了一种新的设计策略.