Ethylene Polymerization over Metal–Organic Framework Crystallites and the Influence of Linkers on Their Fracturing Process,ACS Catalysis

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Ethylene Polymerization over Metal–Organic Framework Crystallites and the Influence of Linkers on Their Fracturing Process
ACS Catalysis ( IF 11.3 ) Pub Date : 2019-03-11 00:00:00 , DOI: 10.1021/acscatal.9b00150
Miguel Rivera-Torrente ₁ , Paul D. Pletcher ₁ , Maarten K. Jongkind ₁ , Nikolaos Nikolopoulos ₁ , Bert M. Weckhuysen ₁

Affiliation

The physical properties and morphologies of polymers are pivotal for their manufacturing and processing at the industrial scale. Here, we present the formation of either fibers or micrometer-sized polyethylene beads by using the MIL-100(Cr) and MIL-101(Cr) zeotypes. The MOF structures have been used for ethylene polymerization with diethylaluminum chloride (DEA) as a cocatalyst, resulting in very different activities and morphologies. In situ DR UV–vis–NIR and CO-probe FT-IR spectroscopy revealed the formation of different types of Cr species for each catalyst material, suggesting that the linker (for the same metal and topological structure) plays a crucial role in the formation of Cr olefin polymerization sites. Activity in ethylene polymerization in toluene at 10 bar and 298 K was related to the observed spectra, corroborating the presence of different types of active sites, by their different activities for high-density polyethylene (HDPE) formation. SEM micrographs revealed that although MIL-100 and MIL-101 exhibit identical zeolitic MTN topology, only the latter is able to collapse upon addition of DEA and subsequent ethylene insertion and to fracture forming polymer beads, thus showing noticeable activity in HDPE formation. We ascribed this effect to the higher pore volume and, thus, fragility of MIL-101, which allowed for polymer formation within its larger cages. MOFs were compared to the nonporous chromium(III) benzoate [Cr₃O(O₂CPh)₆(H₂O)₂](NO₃)·nH₂O complex (1), in order to study the effect of the embodiment in the porous framework. The properties of the polymer obtained under identical reaction conditions were comparable to that of MIL-101(Cr) but very different morphologies were observed, indicating that the MIL-101(Cr) structure is necessary to impart a certain architecture at the microscale. This work clearly shows that MOFs can be used as catalytically active morphology regulators for ethylene polymerization. Moreover, even for an identical topology and metal in a MOF structure, the linker and the pore structure play crucial roles and have to be carefully considered in the design microporous coordination polymers for catalytic purposes.

中文翻译：

金属有机骨架微晶上的乙烯聚合及其连接剂对其压裂过程的影响

聚合物的物理性质和形态对于它们在工业规模上的制造和加工至关重要。在这里，我们介绍通过使用MIL-100（Cr）和MIL-101（Cr）分子型来形成纤维或微米级聚乙烯珠。MOF结构已用于以二乙基氯化铝（DEA）作为助催化剂进行乙烯聚合，从而产生了截然不同的活性和形态。原位DR UV-vis-NIR和CO-探针FT-IR光谱揭示了每种催化剂材料形成不同类型的Cr的物种，这表明连接剂（对于相同的金属和拓扑结构）在形成过程中起着至关重要的作用Cr烯烃聚合位点。在10 bar和298 K的甲苯中，乙烯在乙烯中的聚合活性与所观察到的光谱有关，通过它们对高密度聚乙烯（HDPE）形成的不同活性，证实了不同类型的活性位点的存在。SEM显微照片显示，尽管MIL-100和MIL-101表现出相同的沸石MTN拓扑结构，但是只有后者在加入DEA和随后的乙烯插入时能够塌陷并断裂形成聚合物珠粒，从而在HDPE形成中显示出明显的活性。我们将此效应归因于较高的孔体积，因此是MIL-101的脆性，这使得聚合物可以在其较大的笼中形成。将MOF与无孔苯甲酸铬（III）[Cr 只有后者能够在添加DEA和随后的乙烯插入时崩溃，并使聚合物珠断裂，从而在HDPE形成中显示出明显的活性。我们将此效应归因于较高的孔体积，因此是MIL-101的脆性，这使得聚合物可以在其较大的笼中形成。将MOF与无孔苯甲酸铬（III）[Cr 只有后者能够在添加DEA和随后的乙烯插入时崩溃，并使聚合物珠断裂，从而在HDPE形成中显示出明显的活性。我们将此效应归因于较高的孔体积，因此是MIL-101的脆性，这使得聚合物可以在其较大的笼中形成。将MOF与无孔苯甲酸铬（III）[Cr₃ O（O ₂ CPh）₆（H ₂ O）₂ ]（NO ₃）· n H ₂ O络合物（1），以研究实施例在多孔框架中的效果。在相同的反应条件下获得的聚合物的性能与MIL-101（Cr）相当，但是观察到非常不同的形貌，表明MIL-101（Cr）结构对于在微观尺度上赋予一定的结构是必要的。这项工作清楚地表明，MOF可用作乙烯聚合的催化活性形态调节剂。此外，即使对于MOF结构中相同的拓扑结构和金属，连接基和孔结构也起着至关重要的作用，在设计用于催化目的的微孔配位聚合物时必须仔细考虑。

更新日期：2019-03-11

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