Materials
Zinc nitrate hexahydrate (Zn (NO3)2·6H2O, 99.99%), 2-methylimidazole (Hmim, 98%), and Tetraethyl orthosilicate (TEOS, 98%) were supplied by Shanghai Aladdin Industrial Corporation China. PVDF porous support membrane was prepared using the nonsolvent-induced phase separation (NIPS) method. Dibutyltin dilaurate (DBTDL, ≥96%) was supplied by Tianjin Guangfu Fine Chemical Research Institute China. Hydroxyl-terminated PDMS (viscosity, 50000 mPa s) was purchased from Beijing Chemical Works China. Methanol of analytical grade was purchased from Beijing Tongguang Fine Chemical Company China. Butadiene and nitrogen pure gases (99.999%) were supplied by Shanxi Hongwei Gas Company China. All reagents were used as received without any further purification.