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首页> 外文期刊>Catalysis science & technology >Ethylene polymerization with a crystallographically well-defined metal–organic framework supported catalyst
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Ethylene polymerization with a crystallographically well-defined metal–organic framework supported catalyst

机译：乙烯聚合具有晶体学上定义明确的金属有机框架的催化剂

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The inherent crystallinity of metal–organic framework (MOF) catalysts offers the possibility to understand the structure of the active site at the molecular level. This property is often lacking in traditional amorphous supports. Cr-SIM-NU-1000, a MOF-supported Cr3+ heterogeneous catalyst, is shown to be competent for ethylene polymerization after activation with AlEt2Cl (DEAC), producing crystalline linear polyethylene (PE). The polymer produced has a low polydispersity (Đ = 2.0), in marked contrast to the Phillips supported chromium catalyst, Cr@SiO2 (Đ ∼ 8–65). Cr-SIM-NU-1000 achieves a turnover frequency of 2.6 × 103 h−1 under 40 bar ethylene pressure at room temperature, with corresponding PE productivity of 1.3 × 105 g PE mol−1 Cr per h. Single crystal X-ray diffraction (SC-XRD) of the pre-catalyst was conducted by collecting a structure of alkyl aluminum (DEAC) co-catalyst treated Cr-SIM-NU-1000. This crystal structure provides insight into the interactions between DEAC co-catalyst and Cr active site, revealing a Cr–C bond after treatment with DEAC. Furthermore, DEAC is crystallographically resolved at the terminal oxy-ligands of the node and likely also exists within the window pores of the framework between nodes, based on electron density mapping. Cr-SIM-NU-1000 offers the opportunity to study a structurally well-defined olefin polymerization system, with atomically precise characterization of the pre-catalyst structure. This allows the proposal of a mechanism and feeds into future development of next-generation heterogeneous catalyst systems.
机译：金属有机框架（MOF）催化剂的固有结晶度提供了了解分子水平上活性位点的结构的可能性。传统的无定形支持通常缺乏此属性。 CR-SIM-NU-1000是一种由MOF支持的CR3+异质催化剂，被证明在用Alet2CL（DEAC）激活后具有乙烯聚合具有胜任，从而产生结晶线性聚乙烯（PE）。产生的聚合物具有低分散性（°= 2.0），与菲利普斯支持的铬催化剂（cr@sio2（°〜8-65））形成鲜明对比。 CR-SIM-NU-1000在室温下在40 bar乙烯压力下达到2.6×103 H-1的周转频率，相应的PE生产率为1.3×105 g PE mol-1 Cr / h。通过收集经处理的CR-SIM-NU-1000处理的烷基铝（DEAC）共催化剂结构来进行前催化剂的单晶X射线衍射（SC-XRD）。这种晶体结构可深入了解DEAC共催化剂和CR活性位点之间的相互作用，从而揭示了用DEAC处理后CR – C键。此外，DEAC在节点的末端氧配体上进行结晶解析，并且基于电子密度映射的节点之间的框架孔孔的窗口孔内也可能存在。 CRIM-NU-1000提供了研究结构定义明确的烯烃聚合系统的机会，并具有原子催化剂结构的原子表征。这允许提出一种机制，并融入下一代异质催化剂系统的未来发展。

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