Graphitic carbon nitride materials: variation of structure and morphology and their use as metal-free catalysts
Graphitic carbon nitride materials: variation of structure and morphology and their use as metal-free catalysts
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DOI：
10.1039/b800274f
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发表时间：
2008-01-01
影响因子：
--
通讯作者：
Carlsson, Johan M.
中科院分区：
文献类型：
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作者：
Thomas, Arne;Fischer, Anna;Carlsson, Johan M.
石墨碳氮化物，g-C3 N4，可以通过氰胺、双氰胺或三聚氰胺的聚合来制备。取决于反应条件，获得具有不同缩合度、性质和反应性的不同材料。首先形成的聚合C3 N4结构，甜瓜，与侧氨基，是一个高度有序的聚合物。进一步的反应导致更多的缩合和更少的缺陷的C3 N4物种，基于三-s-三嗪（C6 N7）单元作为基本结构单元。高分辨率透射电子显微镜证明了扩展的二维字符的缩合基序。由于从液体前体的聚合型合成，可以获得各种材料纳米结构，如纳米颗粒或介孔粉末。这些纳米结构还允许微调性能，嵌入的能力，以及为非均相反应提供表面丰富的材料的可能性。由于氮化碳的特殊半导体性质，它们对各种反应显示出意想不到的催化活性，例如苯的活化、三聚反应以及二氧化碳的活化。模型计算来解释这种不寻常的情况下，多相，无金属催化。氮化碳也可以作为非均相反应物，并且可以从相应的氧化物获得新的金属氮化物纳米结构家族。
Graphitic carbon nitride, g-C3N4, can be made by polymerization of cyanamide, dicyandiamide or melamine. Depending on reaction conditions, different materials with different degrees of condensation, properties and reactivities are obtained. The firstly formed polymeric C3N4 structure, melon, with pendant amino groups, is a highly ordered polymer. Further reaction leads to more condensed and less defective C3N4 species, based on tri-s-triazine (C6N7) units as elementary building blocks. High resolution transmission electron microscopy proves the extended two-dimensional character of the condensation motif. Due to the polymerization-type synthesis from a liquid precursor, a variety of material nanostructures such as nanoparticles or mesoporous powders can be accessed. Those nanostructures also allow fine tuning of properties, the ability for intercalation, as well as the possibility to give surface-rich materials for heterogeneous reactions. Due to the special semiconductor properties of carbon nitrides, they show unexpected catalytic activity for a variety of reactions, such as for the activation of benzene, trimerization reactions, and also the activation of carbon dioxide. Model calculations are presented to explain this unusual case of heterogeneous, metal-free catalysis. Carbon nitride can also act as a heterogeneous reactant, and a new family of metal nitride nanostructures can be accessed from the corresponding oxides.