# Ionic Liquid-Modified Porous Organic Polymers as Efficient Metallocene Catalyst Supports
## 1 Introduction  
Since [PERSON] and [PERSON] discovered polymerization activity could be greatly improved by methylaluminoxane (MAO), the manufacture of metallocene polyolefins with controlled chain structure and narrow molecular weight distribution developed rapidly, and the metallocene and post-metallocene catalysts attract great attention of chemists [1, 2, 3, 4, 5]. Nevertheless, metallocene catalysts cause reactor fouling, and most industrial olefin polymerization is conducted in gas or slurry process with heterogeneous catalysts. Therefore, the metallocene/MAO catalysts should be immobilized on support to avoid reactor fouling, to help control the morphology of polymer particles and to reduce the cost of cocatalyst [6, 7].  
A great number of publications reported inorganic and organic porous materials as metallocene supports. Inorganic supports, represented by SiO\({}_{2}\), Al\({}_{2}\)O\({}_{3}\) and zeolite with hard surface and massive acidic groups, may cause a problem of deactivation and high cocatalyst costs [8, 9, 10, 11, 12, 13, 14, 15, 16]. In comparison, kinds of soft organic supports such as polystyrene, polysiloxane and POPs [17, 18, 19, 20, 21, 22, 23] provide an analogous environment to homogeneous polymerization and could be used without complex pre-treatment [24]. A series of functionalized POPs with tunable pore structures were synthesized by our team, they showed better catalytic activity than silica supports, and can be optimized by changing the functional comonomerfor better immobilization, introducing metal oxide templates and altering the solvent to acquire well-shaped particles.  
More recently, the molten salts named ionic liquids (ILs) aroused attention in the field of materials science, which has witnessed widely development in heterogeneous catalysts. The combination of the anion and the cation gives ILs special physical and chemical properties of low volatility, high thermal stability and ion conductivity, etc.; moreover, the typical composition also provides ILs a multiple synthetic choice and diverse applications as a platform compound [25; 26; 27; 28]. In a recent work, [PERSON] et al. used ionic liquid-modified silica (SIL)-supported metallocene to catalyze ethylene polymerization and obtained linear polyethylene with a high melting temperature and crystallinity, thus proving that the ionic liquid could be used as an olefin polymerization catalyst component [29]. Compared to the POPs supports through one-pot synthesis, the SIL supports were prepared under strict conditions by a complex synthetic route.  
Considering that the typical ionic composition of ILs may have a positive effect on MAO/metallocene immobilization, we introduce 1-butyl-3-vinylimidazolium-chloride ([BVIM] [CI]) as a functional comonomer for the synthesis of mono-functional-group and dual-functional-group IL-POPs. The prepared IL-POPs obtained good porosity, and the pore structure can be modulated by adjusting the comonomer contents and solvent system. IL-POPs supports exhibited great ethylene polymerization activity, which would be potential supports for the future heterogeneous olefin polymerization industry.