二维[Ni(1,4-pda)(tib)(H_(2)O)]·H_(2)O的合成及其光催化降解亚甲基蓝

Synthesis of 2D[Ni(1,4-pda)(tib)(H_(2)O)]·H_(2)O and Its Photocatalytic Degradation of Methylene Blue

半导体配位聚合物因结构可调,比表面积大,拥有优异的选择性、稳定性及灵敏性,作为光催化剂在消除废水中的污染物方面引起了研究人员的广泛关注。利用柔性对苯二乙酸(1,4-pda)、刚性三咪唑苯(tib)合成配位聚合物[Ni(1,4-pda)(tib)(H_(2)O)]·H_(2)O。晶体结构分析表明:该晶体属于单斜晶系,空间群为Cc,a=2.0203(3)nm,b=1.2312(17)nm,c=1.1550(17)nm,α=γ=90°,β=106.648(2)°,V=2.7525(7)nm^(3),Z=4。[Ni(1,4-pda)(tib)(H_(2)O)]·H_(2)O的基本结构单元由1个Ni(Ⅱ)、1个对苯二乙酸、1个均苯三咪唑、1个配位水分子和1个结晶水分子组成。三链接均苯三咪唑与中心Ni(Ⅱ)形成波浪二维面,顺式对苯二乙酸与中心Ni(Ⅱ)形成一维波浪链,一维链贯穿于二维面形成有孔洞的二维层,相邻层的对苯二乙酸互相穿插构成复杂的三维超分子结构。同时对[Ni(1,4-pda)(tib)(H_(2)O)]·H_(2)O的热稳定性、循环实验稳定性和紫外可见光进行了检测,发现其基本骨架在300℃开始分解塌陷,5次循环基本骨架稳定,带隙能量小于3.0 eV,可作为稳定的光催化剂。在水体系中[Ni(1,4-pda)(tib)(H_(2)O)]·H_(2)O对亚甲基蓝染料进行光催化降解,降解率为278.62%。主要的光催化降解机制为:[Ni(1,4-pda)(tib)(H_(2)O)]·H_(2)O与H_(2)O2之间容易接触形成一定的协同作用,产生更多的·OH活性物质对染料分子进行氧化降解,最终降解产物为CO_(2)和H_(2)O。

Semiconductor coordination polymers have attracted wide attention as photocatalysts to eliminate pollutants in wastewater due to their adjustable structure,large specific surface area and excellent selectivity,stability and sensitivity.Coordination polymer[Ni(1,4-pda)(tib)(H_(2)O)]·H_(2)O is synthesized by using flexible phenyldiacetic acid(1,4-pda)and rigid 1,3,5-tris(1-imidazolyl)benzene(tib).Crystal structure analysis shows that[Ni(1,4-pda)(tib)(H_(2)O)]·H_(2)O belongs to monoclinic crystal system,and space group is Cc,a=2.0203(3)nm,b=1.2312(17)nm,c=1.1550(17)nm,α=γ=90°,β=106.648(2)°,V=2.7525(7)nm^(3),Z=4.The basic structural unit of[Ni(1,4-pda)(tib)(H_(2)O)]·H_(2)O consists of one Ni(Ⅱ)ion,one 1,4-pda,one tib and one coordinated H_(2)O and one crystalline H_(2)O.The three-linked tib ligands form a wavy 2D surface with the central Ni(Ⅱ).Cis-ppda ligands form a 1D wave chain with central Ni(Ⅱ).1D chains run through a 2D layer form in a 2D surface with holes.The 1,4-pda of adjacent layers are interspersed with each other to form a complex 3D supramolecular structure.[Ni(1,4-pda)(tib)(H_(2)O)]·H_(2)O is also tested for thermal stability,experimental cycle stability and UV visible light.It is found that the basic skeleton starts to collapse at 300℃,the basic skeleton is stable in 5 cycles,and the band gap energy is less than 3.0 eV,which can be used as a stable catalytic material.In the water system,[Ni(1,4-pda)(tib)(H_(2)O)]·H_(2)O performs the photocatalytic degradation of the methylene blue dye with a degradation rate of 78.62%.Major photocatalytic degradation mechanisms:[Ni(1,4-pda)(tib)(H_(2)O)]·H_(2)O and H_(2)O_(2)are easy to form a certain synergy,producing more·OH active substances for oxidative degradation of dye,and the final degradation products are CO_(2)and H_(2)O.