Metal-free β-ketoenamine-based conjugated microporous polymers: rational design of robust photocatalysts for efficient organic pollutant degradation

IF 6.3 3区工程技术 Q1 ENGINEERING, CHEMICAL

Journal of the Taiwan Institute of Chemical Engineers Pub Date : 2025-09-29 DOI:10.1016/j.jtice.2025.106434

Mohamed Gamal Mohamed , Yang‐Chin Kao , Shi-Quan Hong , Aya Farouk Farghal , Shiao-Wei Kuo

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引用次数: 0

Abstract

Background

The rapid growth of industrialization has led to increased discharge of dye-laden wastewater, posing serious threats to aquatic ecosystems and water sustainability. Synthetic dyes like rhodamine B (RhB) and methylene blue (MB), known for their stable conjugated structures, resist biodegradation and persist in the environment. Their accumulation in water bodies harms aquatic life and can indirectly impact human health.

Methods

A series of metal-free β-ketoenamine-based conjugated microporous polymers (CMPs) was synthesized via Schiff-base polycondensation of an amine-terminated azobenzene monomer (AZO-2NH₂), 2,4,6-triformylphloroglucinol (TFP), and a diamino-substituted dibenzothiophene dioxide monomer (DBTD-2NH₂) under solvothermal conditions. By varying the molar feed ratio of AZO-2NH₂:TFP:DBTD-2NH₂ (2:2:1, 1.5:2:1.5, and 1:2:2), three CMP (AZO₂-TFP₂-DBTD₁, AZO_1.5-TFP₂-DBTD_1.5, AZO₁-TFP₂-DBTD₂) with tunable porosity, electronic structure, and morphology were obtained. Comprehensive spectroscopic characterization confirmed the complete formation of β-ketoenamine linkages, the successful incorporation of azo and DBTD motifs, and high chemical purity.

Significant Findings

Thermogravimetric analysis of AZO-TFP-DBTD CMPs revealed outstanding thermal stability (T_d10 up to 461 °C, char yield up to 60.8 wt%). Nitrogen sorption studies demonstrated that our AZO-TFP-DBTD CMPs exhibited hierarchical micro- and mesoporosity, with Brunauer–Emmett–Teller (BET) surface areas ranging from 110 to 125 m² g⁻¹ and dominant pore diameters of 1.7-2.0 nm. Ultraviolet photoelectron spectroscopy (UPS) and Tauc plot analyses of AZO-TFP-DBTD CMPs revealed a progressive deepening of the highest occupied molecular orbital (HOMO) level and a narrowing of the optical bandgaps (2.12-2.19 eV) as the DBTD content increased, thereby enhancing visible-light absorption. Photocatalytic evaluation using methylene blue (MB) and rhodamine B (RhB) as model dyes under visible irradiation revealed that AZO₁-TFP₂-DBTD₂ outperformed its counterparts, achieving greater than 98% degradation within 60 min and pseudo-first-order rate constants of up to 0.067 min⁻¹. Mechanistic studies identified singlet oxygen and photo-generated electrons as the primary reactive species. Recyclability tests of AZO₁-TFP₂-DBTD₂ confirmed excellent stability over three cycles with <10% loss in activity. This work highlights the effectiveness of molecular engineering and monomer stoichiometry in optimizing AZO-TFP-DBTD CMP photocatalysts for water remediation.

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无金属β-酮胺基共轭微孔聚合物：高效降解有机污染物的稳健光催化剂的合理设计

工业化的快速发展导致含染料废水的排放量增加，对水生生态系统和水的可持续性构成严重威胁。合成染料如罗丹明B （RhB）和亚甲基蓝（MB），以其稳定的共轭结构而闻名，抗生物降解并在环境中持续存在。它们在水体中的积累危害水生生物，并间接影响人类健康。方法以氨基端偶氮苯（AZO-2NH2）、2,4,6-三甲酰间苯三酚（TFP）和二氨基取代二苯并噻吩（DBTD-2NH2）为单体，在溶剂热条件下采用席夫碱缩聚法合成了一系列无金属β-酮胺胺基共轭微孔聚合物（cmp）。通过改变AZO-2NH2:TFP:DBTD-2NH2的摩尔投料比（2:2:1,1.5:2:1.5和1:2:2），得到了3种孔隙度、电子结构和形貌均可调节的CMP （AZO2-TFP2-DBTD1, AZO1.5-TFP2-DBTD1.5, AZO1-TFP2-DBTD2）。全面的光谱表征证实了β-酮胺键的完整形成，偶氮基序和DBTD基序的成功结合，化学纯度高。热重分析显示AZO-TFP-DBTD CMPs具有出色的热稳定性（Td10高达461°C，炭收率高达60.8 wt%）。氮吸附研究表明，我们的AZO-TFP-DBTD cmp具有分层的微孔和介孔，其比表面积为110至125 m2 g−1，主要孔径为1.7-2.0 nm。紫外光电子能谱（UPS）和Tauc图分析显示，随着DBTD含量的增加，AZO-TFP-DBTD CMPs的最高已占据分子轨道（HOMO）水平逐渐加深，光学带隙（2.12-2.19 eV）逐渐缩小，从而增强了可见光吸收。在可见光照射下，以亚甲基蓝（MB）和罗丹明B （RhB）为模型染料进行光催化评价，结果表明azo1 - tff2 - dbtd2的降解效果优于同类染料，在60 min内达到98%以上的降解效果，伪一级速率常数高达0.067 min−1。机理研究确定单线态氧和光生电子是主要的反应物质。AZO1-TFP2-DBTD2的可回收性试验证实，在三次循环中，AZO1-TFP2-DBTD2具有优异的稳定性，活性损失为10%。这项工作强调了分子工程和单体化学计量学在优化AZO-TFP-DBTD CMP光催化剂用于水修复中的有效性。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Journal of the Taiwan Institute of Chemical Engineers 工程技术-工程：化工

CiteScore

9.10

自引率

14.00%

发文量

362

审稿时长

35 days

期刊介绍： Journal of the Taiwan Institute of Chemical Engineers (formerly known as Journal of the Chinese Institute of Chemical Engineers) publishes original works, from fundamental principles to practical applications, in the broad field of chemical engineering with special focus on three aspects: Chemical and Biomolecular Science and Technology, Energy and Environmental Science and Technology, and Materials Science and Technology. Authors should choose for their manuscript an appropriate aspect section and a few related classifications when submitting to the journal online.