Starbons: New starch-derived mesoporous carbonaceous materials with tunable properties
Starbons: New starch-derived mesoporous carbonaceous materials with tunable properties
复制标题
DOI：
10.1002/anie.200600460
复制
发表时间：
2006-01-01
影响因子：
16.6
通讯作者：
Wilson, Ashley J.
中科院分区：
文献类型：
--
作者：
Budarin, Vitaly;Clark, James H.;Wilson, Ashley J.
中孔碳质材料的突出潜力[1]需要一种方法赠款控制其表面化学和孔径分布。目前实现孔径分布控制的最佳方法是模板法。一个典型的过程[1c]涉及用碳前体（例如蔗糖）填充中孔二氧化硅，随后通过一系列高温过程进行煅烧。然后用氢氟酸或苛性钠除去模板。通过这种方法生产的活性炭具有有序的介孔结构，具有大的比体积和物理性能，适用于广泛的应用。[2]然而，所涉及的高度侵蚀性化学品限制了这种方法生产具有惰性疏水表面的稳定石墨碳。[3]为了功能化和开辟新的化学，需要进一步困难的化学修饰。这是以降低中孔的可用性为代价的。[4]在这里，我们报告了一种新的方法，用于生成一个新的家庭的介孔碳质材料的表面范围从亲水性到疏水性，这是由碳化程度控制。该方法利用淀粉颗粒内的直链淀粉和支链淀粉聚合物链的天然能力来组装成有组织的纳米级层状结构，其由结晶和无定形区域组成。[5]我们的策略是通过使用中孔膨胀淀粉[6]作为前体而不需要模板剂来合成中孔碳（以下称为“starbons”）。该过程是温和的，并且提供了生产从淀粉到活性炭的整个范围的中孔碳基材料的机会，包括具有许多应用的无定形含氧碳，[7]例如催化，[7 a，B]吸附，[7 c]和药物，[7 d，e]由于其不同的表面官能度。首先，在水中凝胶化的简单过程打开并扰乱了致密的生物聚合物网络，[8]之后，它在凝沉过程中部分重结晶。[9]用较低表面张力的溶剂（通常是乙醇）交换水可以防止干燥过程中网络结构的崩溃。干燥后得到膨胀的介孔淀粉。在该过程的最后阶段，中孔淀粉掺杂有催化量的有机酸（例如对甲苯磺酸）并在真空下加热。这使得能够快速碳化和固定中孔结构。在150至700 ℃的不同温度下加热可以产生从无定形碳到类石墨活性炭的各种中孔材料。天然淀粉颗粒不产生介孔材料时，粉碎。这表明作为淀粉前体的膨胀淀粉的形成是至关重要的。
The outstanding potential of mesoporous carbonaceous materials [1] requires a methodology that grants control over their surface chemistry and the distribution of pore sizes. The best current method that achieves control over pore-size distribution is the templating method. A typical procedure [1c] involves filling mesoporous silica with a carbon precursor (eg sucrose), which is subsequently carbonized through a series of high-temperature processes. The template is then removed by using hydrofluoric acid or caustic soda. The resultant activated carbons produced by this method possess wellordered mesoporous structures with a large specific volume and physical properties amenable to a broad range of applications.[2] However, highly aggressive chemicals involved limit this approach to the production of stable graphitic carbons with inert hydrophobic surfaces.[3] To functionalize and open up new chemistry, further difficult chemical modifications are required. This is at the cost of reducing the availability of the mesopores.[4] Herein we report a novel approach for the generation of a new family of mesoporous carbonaceous materials with surfaces ranging from hydrophilic to hydrophobic, which is controlled by the degree of carbonization. The method utilizes the natural ability of the amylose and amylopectin polymer chains within the starch granules to assemble into an organized nanoscale lamellar structure, which consists of crystalline and amorphous regions.[5] Our strategy was to synthesize mesoporous carbons (hereinafter referred to as “starbons”) by using mesoporous expanded starch [6] as the precursor without the need for a templating agent. This process is gentle and provides the opportunity to produce a whole range of mesoporous carbon-based materials from starch to activated carbon, including amorphous oxygencontaining carbons that have many applications,[7] such as catalysis,[7a, b] adsorption,[7c] and medicine,[7d, e] owing to their varied surface functionalities.The approach described is illustrated in Scheme 1. First, a simple process of gelatization in water opens up and disorders the dense biopolymer network,[8] after which it partially recrystallizes during a process of retrogradation.[9] Exchanging water with a lower-surface-tension solvent (usually ethanol) prevents collapse of the network structure during the drying process. After drying, the expanded mesoporous starch is obtained. In the final stage of the process, mesoporous starch is doped with a catalytic amount of organic acid (eg para-toluenesulfonic acid) and heated under vacuum. This enables fast carbonization and fixing of the mesoporous structure. Heating at different temperatures, ranging from 150 to 7008C has produced a variety of mesoporous materials from amorphous carbons to graphite-like activated carbons. Native starch granules do not produce mesoporous materials when carbonized. This indicates that the formation of expanded starch as a precursor to starbon is crucial.