Dipole polarization modulating of vinylene-linked covalent organic frameworks for efficient photocatalytic hydrogen evolution  

通过偶极极化调制乙烯键连接的共价有机框架以实现高效光催化析氢

作　　者：Ming Wang Yaling Li Dengxin Yan Hui Hu a Yujie Song Xiaofang Su Jiamin Sun Songtao Xiao Yanan Gao 王日明;李亚玲;严登鑫;胡慧;宋玉洁;苏晓芳;孙佳敏;肖松涛;高艳安(海南大学热带岛屿资源先进材料教育部重点实验室,海南海口570228;根特大学化学技术实验室,比利时根特;中国原子能科学研究院,北京102413)

机构地区：[1]Key Laboratory of Ministry of Education for Advanced Materials in Tropical Island Resources,Hainan University,Haikou 570228,Hainan,China [2]Laboratory for Chemical Technology,Ghent University,Technologiepark 125,9052 Gent,Belgium [3]China Institute of Atomic Energy,Beijing 102413,China

出　　处：《Chinese Journal of Catalysis》2024年第10期103-112,共10页催化学报（英文）

基　　金：海南省重点研发计划(ZDYF2024GXJS005);海南省重大科技计划(ZDKJ202016);国家自然科学基金(21965011,22105053).

摘　　要：Photocatalytic hydrogen(H_(2))evolution using covalent organic frameworks(COFs)is an attractive and promising avenue for exploration,but one of its big challenges is low photo-induced charge separation.In this study,we present a straightforward and facile dipole polarization engineering strategy to enhance charge separation efficiency,achieved through atomic modulation(O,S,and Se)of the COF monomer.Our findings demonstrate that incorporating atoms with varying electronegativities into the COF matrix significantly influences the local dipole moment,thereby affecting charge separation efficiency and photostability,which in turn affects the rates of photocatalytic H_(2) evolution.As a result,the newly developed TMT-BO-COF,which contains highly electronegative O atoms,exhibits the lowest exciton binding energy,the highest efficiency in charge separation and transportation,and the longest lifetime of the active charges.This leads to an impressive average H_(2) production rate of 23.7 mmol g^(−1) h^(−1),which is 2.5 and 24.5 times higher than that of TMT-BS-COF(containing S atoms)and TMT-BSe-COF(containing Se atoms),respectively.A novel photocatalytic hydrogen evolution mechanism based on proton-coupled electron transfer on N in the structure of triazine rings in vinylene-linked COFs is proposed by theoretical calculations.Our findings provide new insights into the design of highly photoactive organic framework materials for H_(2) evolution and beyond.利用太阳辐照直接从水中制备氢气被认为是一种环保的、可持续的氢气生产方式.共价有机框架(COFs)因在光催化析氢反应中表现出良好的性能,而成为研究热点。在众多COFs类型中,亚胺键连接的COFs因其独特的结构特性而得到了广泛关注.然而,亚胺键的存在往往伴随着稳定性不足和共轭性较弱的问题,限制了其光催化性能.相比之下,乙烯键连接的COFs由于具有稳固的连接键,显示出更高的稳定性。此外,局域偶极极化效应能够通过内置电场作用,有效提升电子-空穴对的分离效率,是优化光催化性能的重要途径之一然而,目前关于乙烯键连接的COFs在局域偶极极化光催化方面的研究较少.本文主要考察了光催化析氢反应中乙烯键连接的COFs的设计、合成及其性能研究.首先,以具有光活性的2,4,6-三甲基-1,3,5-三嗪(TMT)为构筑基元,分别与4,4'-(苯并呋咱-4,7-二基)二苯甲醛(BO)、4,4'-(苯并噻二唑-4,7-二基)二苯甲醛(BS)和4,4-(苯并硒二唑-4,7-二基)二苯甲醛(BSe)进行羟醛缩合反应,成功合成了三种乙烯键连接的COFs,即TMT-BO-COF,TMT-BS-COF和TMT-BSe-COF.粉末X射线衍射、高分辨透射电镜和N,吸脱附结果表明,三种COFs均具有高结晶性和比表面积.傅里叶红外光谱、固体核磁和X射线光电子能谱进一步证实了三种COFs材料的成功合成.在性能测试中发现,这些COFs在可见光区域具有强吸收能力,且其光学带隙与导带位置适宜,预示着可能具有较好的光催化析氢活性。进一步研究表明,局域偶极矩对光催化析氢效率有重要影响.通过局域偶极矩计算和光催化析氢实验研究发现,TMT-BO-COF因其结构中高电负性氧原子的存在,展现出最大的局域偶极矩(3.8992D),有效促进了电子-空穴对分离,实现了高效的光催化析氢。其产氢速率高达23.7mmol g^(-1)h^(-1),远高于TMT-BS-COF(9.45mmol g^(-1)h^(-1))和TMT-BSe-COF(0.96mmol g^(-1)h^(-1))为了深�

关 键 词：Covalent organic framework Vinylene linkage ELECTRONEGATIVITY Dipole polarization Photocatalytic hydrogen evolution 

分 类 号：O62[理学—有机化学]