单层ZIF67纳米颗粒修饰的C3N4在可见光下光催化降解有机污染物

C3N4 modified with single layer ZIF67 nanoparticles for efficient photocatalytic degradation of organic pollutants under visible light

随着全球工业化水平的提高,有机污染物引起的水环境问题也日益严重.针对有机污染物表现出的持久性和难降解性等问题,全球科研工作者提出了不同的方法去治理相关环境问题.其中利用光催化降解有机污染物作为一种新兴技术,因处理成本低、污染物降解效率高、光催化剂可回收利用等优点受到越来越多的关注.在诸多的光催化剂中,氮化碳(C3N4)拥有2.7 eV的能带宽度,且其合成简单,价格低廉,环境友好,以及在可见光下即可催化降解污染物等特点而被广泛研究.但是,比表面积小和易与光激发电荷载流子结合等缺点也制约C3N4的广泛应用.针对上述问题,本文将具有巨大比表面积的金属骨架材料ZIF67引入到C3N4之中,合成了均匀分布的单层ZIF67衍生的C3N4(ZIF67-C3N4),并将其应用于可见光下的亚甲基蓝(MB)光催化降解.结果表明,所制得的ZIF67-C3N4的最大比表面积可达541.392 m^2/g,远高于未加工的C3N4的97.291 m^2/g.ZIF67-C3N4光催化活性结果表明,2.57 g ZIF67和0.3 g C3N4即ZIF67-C3N4(0.3)表现出优异的光催化活性.加入0.01 g的ZIF67-C3N4(0.3)可以在70 min内降解90%以上的浓度为10 mg/L的亚甲基蓝,而原C3N4在同等条件下处理相同浓度的亚甲基蓝所需的时间超过140 min.同时,本文还考察了溶液的pH值,亚甲基蓝的初始浓度和ZIF67-C3N4复合材料中C3N4的含量等因素对亚甲基蓝光催化降解的影响.结果显示,ZIF67-C3N4(0.3)在碱性条件下降解亚甲基蓝的效率高于中性条件.在pH=12的情况下,ZIF67-C3N4(0.3)可以在10 min内完全降解100 mL的浓度为10 mg/L的亚甲基蓝.此外,在酸性条件下亚甲基蓝的降解效果很差,说明ZIF67-C3N4(0.3)在酸性条件下容易失活.通过对亚甲基蓝初始浓度对光催化反应的研究显示,当亚甲基蓝的初始浓度为20 mg/L时,经140 min反应后,亚甲基蓝的去除率小于90%;当亚甲基蓝的浓度降至15 mg/L时,其在120 min的降解效率超过92%;而10 mg/L的亚甲基蓝可在120 min内完全降解.对制备的五种催化剂对亚甲基蓝的降解效果分析得出ZIF67-C3N4(0.3)比其他四种催化剂的效果更好.为了揭示ZIF67-C3N4(0.3)在可见光条件下催化降解亚甲基蓝的反应机理,本文利用叔丁醇、甲酸以及对苯醌进行淬灭实验.结果表明,光致空穴(h^+)和超氧自由基(O2-·)是降解亚甲基蓝的主要活性物质.

Uniformly distributed single layer of ZIF67-derived C3N4(ZIF67-C3N4)was synthesized and applied to the photocatalytic degradation of methylene blue(MB)under visible light.Results indicated that the obtained ZIF67-C3N4 has a maximum specific surface area of 541.392 m^2/g,which is much larger than that of raw C3N4 of 97.291 m^2/g.The investigation of C3N4 amount involved in ZIF67-C3N4 on the photoactivity revealed that 2.57 g ZIF67 with 0.3 g C3N4,which named ZIF67-C3N4(0.3)exhibited superior photocatalytic activities.More than 90%of MB at 10 mg/L was degraded within 70 min with the addition of 0.01 g ZIF67-C3N4(0.3),while this time required for raw C3N4 was over 140 min.The effects of pH of solution,initial concentration of MB and dosage of C3N4 in ZIF67-C3N4 composites on the photocatalytic efficiency for MB degradation were also evaluated.Quenching experiments indicated that the photo-induced holes(h^+)and superoxide radicals(O2-·)were mainly responsible for MB degradation.It is anticipated that the insertion of ZIF67 nanoparticles not only increases the adsorption capacity of C3N4 but also promotes the generation and migration of the photo-induced active species.