Solar-Light-Driven Renewable Butanol Separation by Core-Shell Ag@ZIF-8 Nanowires
Solar-Light-Driven Renewable Butanol Separation by Core-Shell Ag@ZIF-8 Nanowires
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太阳能光驱动的可再生丁醇通过核壳Ag@ZIF-8纳米线分离
DOI：
10.1002/adma.201405583
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发表时间：
2015-06-03
影响因子：
29.4
通讯作者：
Tang, Zhiyong
中科院分区：
文献类型：
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作者：
Liu, Xu;He, Liangcan;Tang, Zhiyong
DOI: 10.1002 / adma。201405583已成为其实际应用的大关注点。通常，ZIF-8的再生通过两种策略实现：i)在真空或加热下处理，ii)在适当温度下用有机溶剂冲洗，然后去除这些溶剂。[19-21]显然，现有的再生方法要么带来较高的能源成本，要么造成额外的环境污染。因此，设计和构建能够实现生物丁醇分离的高性能、低成本、环境相容性好的高级吸附材料具有重要的科技意义。本研究建议采用新型核壳纳米结构Ag@ ZIF-8吸附分离水中的低浓度丁醇。不同于球形银纳米粒子仅在400 nm左右具有窄表面等离子共振（SPR）吸收，各向异性银纳米线在330-900 nm波长范围内具有强而宽的SPR吸收特性，使其成为理想的太阳能光照射下产热的纳米材料。[23,24]因此，可以想象，如果纳米线与ZIF-8可控地结合，例如，银纳米线均匀地涂覆ZIF-8外壳，太阳光照将取代传统的加热或真空，使ZIF-8再生用于丁醇吸附分离（方案1）。这种不需要昂贵的基础设施就能利用免费阳光的方法有望大大降低生物燃料的生产成本。采用两步法合成了Ag@ ZIF-8纳米线（图1）。首先，采用液相法合成了直径均匀的90-120 nm的聚乙烯吡咯烷酮（PVP）包覆银纳米线（图S1，支持信息）。[25,26]然后，将合成的Ag纳米线与ZIF-8前驱体（Zn (no3) 2·6h2o和2-甲基咪唑酸盐）直接混合在甲醇中，在15℃下搅拌3小时。然后，将混合溶液置于室温下，不搅拌，以使ZIF-8在Ag纳米线表面生长。最后，培养12h后，离心收集固体产物。扫描电镜（SEM）、透射电镜（TEM）和高角度环形暗场扫描透射电镜（HAADF-STEM）观察均显示产物具有明确的核壳结构，大小和形状相似（图1 a-c）。进一步统计结果表明，Ag纳米线芯的直径为107.87±15.05 nm，而ZIF-8的壳厚为57.42±6.94 nm（图S2，支持信息）。能量色散x射线（EDX）元素映射清楚地揭示了Ag元素被限制在核心，而归属于ZIF-8的C、N和Zn元素则是均匀的
DOI: 10.1002/adma. 201405583 has become a big concern for their real application. Generally, regeneration of ZIF-8 is implemented by two strategies: i) treatment under vacuum or heating, and ii) flushing with the organic solvents at modest temperatures followed by removal of these solvents.[19–21] Evidently, current regeneration methods either bring high energy cost or cause additional environment pollution. Therefore, design and construction of the advanced adsorption materials, which could realize separation of biobutanol with high performance, low cost, and good environmental compatibility, is of great scientific and technical significance. Here, we suggest adopting the novel core–shell Ag@ ZIF-8 nanostructures for adsorptive separation of low concentration butanol from water. Unlike spherical Ag nanoparticles that only possess a narrow surface plamson resonance (SPR) absorption at around 400 nm, anisotropic Ag nanowires are known to exhibit strong and broad SPR absorption feature in the wavelength range of 330–900 nm,[22] making them become ideal nanomaterials for heat generation under solar light irradiation.[23, 24] Therefore, one can image that if the nanowires are controllably combined with ZIF-8, eg, Ag nanowires homogenously coated with ZIF-8 shells, solar light irradiation will replace conventional heating or vacuum to regenerate the ZIF-8 for butanol adsorptive separation (Scheme 1). Such utilization of free sunlight without need of expensive infrastructures would be expected to dramatically lower the production cost of biofuels.The core–shell Ag@ ZIF-8 nanowires (Figure 1) were synthesized using a two-step synthesis method. First, the polyvinylpyrrolidone (PVP)-capped Ag nanowires with rather uniform diameters of 90–120 nm (Figure S1, Supporting Information) were synthesized using a solution-phase approach.[25, 26] Subsequently, as-synthesized Ag nanowires were directly mixed with the ZIF-8 precursors (Zn (NO 3) 2· 6H 2O and 2-methylimidazolate) in methanol with stirring at 15 C for 3 h. Afterwards, the mixture solution was placed at room temperature without stirring, in order to allow for growth of ZIF-8 on the surface of the Ag nanowires. Finally, after grown for 12 h, the solid products were collected via centrifugation. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) observations all display that the products have well-defined core–shell structures with similar size and shape (Figure 1 a–c). Further statistics based on the products indicate that the diameter of the Ag nanowire cores is 107.87±15.05 nm, while the thickness of the ZIF-8 shells is 57.42±6.94 nm (Figure S2, Supporting Information). The energy-dispersive X-ray (EDX) elemental mapping clearly discloses that the element Ag is confined in the core whereas the elements C, N, and Zn attributed to ZIF-8 are homogenously