载体和轴向配体对八正丁硫基含硫四氮杂钴卟啉光催化活性的影响

将八正丁硫基四氮杂钴卟啉(CoPz(BuS)8)分别负载到载体Al2O3和SiO2@Fe3O4以及与配体叠氮轴向配位,并在模拟太阳光的氙灯照射下通入空气,通过降解水中染料罗丹明B(RhB)来评估其光催化活性.载体Al2O3有高的比表面积和好的化学惰性,其表面还存在一些氧空位以促进氧化反应中活性氧的流动;虽然磁性纳米颗粒(MNP)Fe3O4表面存在酸腐蚀和自聚集问题,但在MNP外面包覆一层具有较好吸附和稳定性能的SiO2膜,因而也是较好的催化剂载体.富电子的NaN3可增强某些缺电子的过渡金属大环络合物催化氧化反应,是较好的轴向配体.在不同pH水溶液中降解RhB的动力学曲线表明,反应为准一级.复合催化剂CoPz(BuS)8/Al2O3上RhB降解率在pH=4时经160 min达到84.6%,在pH=7和pH=9时经12 h分别达到65.1%和49.2%.复合催化剂CoPz(BuS)8/SiO2@Fe3O4的透射电镜(TEM)和红外光谱(FTIR)表征表明,SiO2包覆完整,复合粒子在1083 cm?1有SiO2的吸收峰,在2910 cm?1有CoPz(BuS)8的烷基吸收峰,说明NMP上存在SiO2和CoPz(BuS)8,表明复合粒子制备成功;其光催化反应的降解率在pH=4,7和9时经12 h分别达到66.3%,41.9%和29.6%.尽管CoPz(BuS)8负载到Al2O3上比负载到SiO2@Fe3O4上活性高,但后者分离容易,可重复使用,尤其是可随时终止反应.这意味着不同的污染物可用性能不同的催化剂/MNP系统去除,而催化剂可高效回收.当富电子的NaN3与CoPz(BuS)8在轴向配位并负载到Al2O3上时,CoPz(BuS)8的紫外-可见光谱B带红移28 nm,Q带红移19 nm,FTIR在2122 cm?1出现一个?N=N+=N?特征吸收峰,临近S原子的烷基链?CH2?的核磁峰从3.17 ppm移向低场4.17 ppm,表明N3?配位成功.利用ESR自由基捕获技术发现,该复合催化剂能活化分子氧,产生比复合催化剂CoPz(BuS)8/Al2O3更多的O2??和HO?等活性物种.在pH=4和pH=7水溶液中的反应明显偏离了一级反应动力学,促进RhB的快速降解,在pH=4时80 min内降解率达到77.6%,之后因RhB浓度迅速降低而慢下来.同时,在pH=7和pH=9时经12 h降解率也分别达到81.7%和74.3%.RhB降解产物主要有N,N-二乙基-N-乙基罗丹明、N,N-二乙基罗丹明、N-乙基罗丹明和罗丹明.其中第一个产物是主要中间体,随后被活性氧物种分裂成小分子和矿化.比较了不同pH媒介中三个复合催化剂的活性,发现酸性条件有利于光催化反应.这是因为在酸性溶液中产生的活性物种比在中性和碱性溶液中多,且随着反应时间增加而增加所致.而在中性和碱性条件下,活性物种改变很少.稳定性实验表明,复合催化剂是稳定的,可以重复使用,复合催化剂CoPz(BuS)8/SiO2@Fe3O4重复使用7次后活性基本保持不变.

Effect of carrier and axial ligand on the photocatalytic activity of cobalt thioporphyrazine

The photocatalytic activity of cobalt octakis(butylthio) porphyrazine (CoPz(BuS)8) was assessed through photodegradation of the dye rhodamine B (RhB) in water under irradiation with a Xe lamp and aerated conditions. The photocatalytic activity of CoPz(BuS)8 loaded on Al2O3 or SiO2@Fe3O4 nanoparticles or coordinated with an axial azide ligand was also investigated. The results demonstrated that the photocatalytic activity of CoPz(BuS)8 loaded on Al2O3 was higher than that loaded on SiO2@Fe3O4. The kinetic curves of RhB degradation in aqueous solutions at different pH indicated the pseudo firstorder kinetics of the reaction. The highest degradation rate for CoPz(BuS)8 loaded Al2O3 at pH=4 after 160 min was 84.6%. However, the advantages of easier separation and recycling as well as the ability to terminate the reaction at any time for the CoPz(BuS)8 loaded SiO2@Fe3O4 cannot be ignored. When electronrich NaN3 was coordinated with CoPz(BuS)8 as an axial ligand and loaded on Al2O3, the resulting catalyst produced more active oxygen species such as O2?and HO?to promote the quicker degradation of RhB than that by the other catalysts. For the N3-coordinated CoPz(BuS)8 loaded on Al2O3, the reactions at pH=4 and 7 distinctly deviated from first-order kinetics, and the degradation rate reached 77.6%after 80 min at pH=4.