文献类型：期刊文献

英文题名：Thiadiazole/Triazole-based covalent organic frameworks for efficient photocatalytic reduction of U(VI): Isomeric effect and delocalization degree

作者：Zhong, Xin[1];Ji, Zhehong[1];Xu, Jing[1]

机构：[1]Shaoxing Univ, Sch Life & Environm Sci, Huancheng West Rd 508, Shaoxing 312000, Peoples R China

年份：2025

卷号：367

外文期刊名：SEPARATION AND PURIFICATION TECHNOLOGY

收录：SCI-EXPANDED(收录号：WOS:001465279600001)、、EI(收录号：20251518195820)、Scopus(收录号：2-s2.0-105001925664)、WOS

基金：Financial support from the Research Fund Program of National Natural Science Foundation of China (No. 22106107) , and Natural Science Foundation of Zhejiang Province (LY23B070003) .

语种：英文

外文关键词：COFs; U(VI); Adsorption; Photocatalyst; Photoreduction

外文摘要：In this work, we synthesized the thiadiazole-containing isomeric COFs (TpTD1 and TpTD2) via heteroatom-tuned strategy, which had the identical molecular formula and similar unit cells, except for the position of the S atom in the five-membered ring of the thiadiazole. Despite bearing the same molecular formula, TpTD1 and TpTD2 exhibited different photoelectrochemical properties. Specifically, the adsorption energy between TpTD2 and UO22+ ion was-11.65 eV which was much lower than that of TpTD1 (-5.26 eV). Under visible light irradiation, the U(VI) photoreduction rate of the asymmetric TpTD2(2.67 x 10-3 min-1) was six times higher than that of the symmetric isomer TpTD1(4.1 x 10-4 min-1). The reason could be attributed to the fact that the dipole moment of TpTD1 was larger than that of TpTD2, which strengthened the electric field polarization and promoted the charge separation and electron transport, and the NBO charge analysis revealed that the electronegativity of N atoms in the thiazole structure of TpTD2 was obviously lower than that of TpTD1, which reinforced the electrostatic adsorption with UO22+ ion. Further, we fabricated D-it-A and D-it-A-A COFs containing triazole (N atoms replacing S atoms, TpDT) and bis(triazole) molecules (Tp-DBT) to extend the it-conjugated system for improving the photocatalytic performance. Due to the stretching of the it-conjugated system, the forbidden bandwidth was shortened from 2.38 (TpDT) to 1.85 eV (Tp-DBT), and the photocurrent was elevated and electrochemical impedance was reduced. Electrostatic potential (ESP) analysis revealed that the electronegativity of N atoms in the triazole of TpDT was noticeably lower than that in Tp-DBT, which was favorable for the adsorption of UO22+ ion. In the meantime, the charge difference between Tp and DT/DBT molecules was 0.069|e-|(TpDT) and 0.027| e-|(Tp-DBT), respectively, suggesting that the built-in electric field strength of TpDT was significantly higher than that of Tp-DBT, which effectively inhibited the photogenerated carrier complexation. Thus, the combined effect resulted in the rate of photocatalytic reduction of U(VI) by TpDT (1.45 x 10-3 min-1) that was approximately twice that of Tp-DBT (1.14 x 10-3 min-1).