Synthesis,Structure Regulation And Properties Of Pyrene-based Covalent Organic Frameworks

Covalent organic frameworks(COFs)are a class of crystalline porous materials,in which the building blocks are connected by covalent bonds through reversible polymerization to achieve the rational synthesis of COFs.Benefiting from the diversity of synthetic routes combined with abundant possibilities of post-synthesis,COFs are outstanding functional materials to fulfill multi-demands,such as carbon dioxide and ammonia capture,gas separation,proton conduction,catalysis,energy conversion/storage,sensing,optoelectronics and biomedicine.Meanwhile,targeted synthesis of COFs according to the structural and functional demands is highly feasible.Taking full advantage of reticular chemistry,COFs with desirable frameworks can be constructed through varying the selections of building knots,linkages and their connection types.In this paper,pyrene derivatives are selected as building nodes to synthesize a series of COFs.The detailed contents are presented as following:1.Two highly crystallized and stable mesoporous COFs,Azo-COF and Tp-COF,are synthesized for the separation of large-size molecules,and their pore size differences less than 4 (?) are obtained via elaborate selection of pyrene knots and amino linkages.The tandem utilization of these two COFs exhibits efficiently size-selective separation ability towards low MW proteins cytochrome c and myoglobin with small MW difference of 2 k Da,in which protein adsorption processes are verified by computational calculations together with confocal laser scanning microscopy.Furthermore,a simple COFs-based separation device is designed and prepared to achieve effective and low-consumption proteins separation.In addition,Azo-COF achieve β2-MG separation from the real urine.This work has offered an optimized synthetic strategy for fine-tuned mesoporous COFs and expanded their applications on macromolecules separation.2.Thiophene derivatives are selected as building blocks to synthesize pyrene-based COFs ORR catalysts.Th-COF and BTh-COF with different numbers of thiophenes in the framework are synthesized.The experimental results show that Th-COF and BTh-COF have following characteristics as effective electrocatalyst for ORR:(1)The COFs is highly tunable so that the number of active sites in the frameworks can be precisely regulated by selecting different thiophene derivatives,which can directly affect their catalytic activity;(2)The synthesis of COFs catalysts is mild.This work makes COFs as an emerging platform for electrocatalysis,which provides theoretical and experimental guidance for the development of metal-free ORR catalysts.3.In order to improve the catalytic performance,thiazole groups are introduced into the frameworks by in-situ synthesis.TP-COF,TTh-COF and TBTh-COF are synthesized by the connection type of thiazole.The experimental results showed that both thiophene and thiazole groups are as effective electrocatalytic active sites in the frameworks.The more catalytically active groups in COFs,the better ORR play.In addition,the half-wave potential of TBTh-COF with the most catalytic sites is 0.724V(vs.reversible hydrogen electrode [RHE]),which indicates that the functionalities of COFs can be effectively regulated by connection type.This work offers a new idea about the construction of metal-free ORR catalysts.