介孔SiO_2包覆Ag/ZIF-8核壳型催化材料的合成

Synthesis of a Core-shell Structured Ag/ZIF-8 Catalyst with Mesoporous Silica Shell

通过液相自组装制备了Ag/ZIF-8;进一步以十六烷基三甲基溴化铵(CTAB)为结构导向剂,在疏水Ag/ZIF-8颗粒表面包覆一层介孔二氧化硅(MS)壳,合成了具有核壳结构的Ag/ZIF-8@MS催化剂,并对其进行了结构和性能表征.结果表明,Ag/ZIF-8@MS具有均一的颗粒尺寸(Ag/ZIF-8@MS粒径约为100 nm,Ag粒径约为15 nm)、较高的比表面积(539 m^2/g)及较大的孔体积(0.64 m^3/g);透射电子显微镜表征结果表明,介孔二氧化硅表层厚度约为20 nm.于550℃煅烧后,催化剂结构转变成Ag/Zn O@MS核壳结构.以催化对硝基苯酚生成对氨基苯酚为模型反应,对2种结构的Ag催化剂的催化性能进行了测试.催化反应结果表明,核壳型结构Ag/ZIF-8@MS材料催化对硝基苯酚反应的转化率超过95%,证明了这种以ZIF-8为载体的核壳型材料的优势.

The self-assembly technique was employed to sythesize the Ag nanoparticles on ZIF-8（Ag/ZIF-8）.Cetyltrimethyl ammonium bromide（CTAB） was used as the structure-directing agent to facilitate mesoporous silica to coat on the surface of hydrophobic Ag/ZIF-8（Ag/ZIF-8@MS）. The prepared Ag/ZIF-8@MS with a core-shell structure was characterized by a series of measurements. The results show that Ag/ZIF-8@ MS has a uniform particle size（Ag/ZIF-8@MS： ca. 100 nm,Ag： ca. 15 nm）,high specific surface area（539 m2/g）and large pore volume（0. 64 m3/g）. The TEM images indicate that the thickness of mesoporous silica shell is ca. 20 nm. The structure of catalyst is transformed into Ag/Zn O@ MS core-shell structure after calcination at550 ℃. Meanwhile,both of the Ag-baesd catalysts were tested for the reaction of 4-nitrophenol to prepare 4-aminophenol. The catalytic results showed that the conversion of 4-nitrophenol catalyzed by Ag/ZIF-8@ MS was more than 95%,which proves the advantage of the core-shell structure with ZIF-8 as a carrier.