无机柱中心强化的二次生长法制备KAUST-7气体分离膜

Preparation of KAUST-7 Gas Separation Membrane by Inorganic Pillar Center-Facilitated Secondary Growth Method

超微孔KAUST-7氟化金属有机骨架化合物具有0.30~0.48 nm的孔道,对于CO_(2)、丙烯等气体具有特异性吸附,是一种潜在的小分子气体分离膜材料。本研究提出采用无机柱中心强化的二次生长法制备KAUST-7膜。首先采用无机柱中心法合成晶种,通过调节合成液中乙醇含量控制晶体的尺度及形貌,得到70 nm的KAUST-7小晶种。由预先合成的无机柱中心(NbOF_(5))^(2-)代替氢氟酸和Nb_(2)O_(5)为氟源及铌源,考察了热浸渍和层层组装法制备的晶种层对于大孔α-Al_(2)O_(3)载体管上二次生长法制备KAUST-7膜的影响。层层组装晶种二次生长法制备出的高性能KAUST-7气体分离膜对于H_(2)的渗透速率为2.23×10^(-7)mol/(m^(-2)·s·Pa),H_(2)/CO_(2)、H_(2)/N_(2)和H_(2)/CH_(4)的理想选择性分别为24.9、17.3和13.0。本方法不但突破了原合成液中含有的氢氟酸对于氧化铝载体的腐蚀导致难以成膜的挑战,而且实现了温和条件下KAUST-7分离膜的制备,也为含腐蚀性反应体系制备分离膜提供了借鉴。

The ultra-microporous KAUST-7 fluorinated metal-organic framework contains pores with a size of 0.30~0.48 nm and has the specific adsorption for propylene and CO_(2),which is a potential membrane material candidate for the separation of small-molecule gases.In this study,the inorganic pillar center-facilitated secondary growth method was proposed to fabricate continuous KAUST-7 membranes.Firstly,KAUST-7 crystals were synthesized via inorganic pillar center-facilitated method.The size and morphology of KAUST-7 crystals were manipulated by adjusting ethanol volume ratio in the solvent,under the optimized condition,nano KAUST-7 crystals(~70 nm)were obtained.The KAUST-7 membrane fabricated by secondary growth onα-Al_(2)O_(3)tubes using(NbOF_(5))^(2-) inorganic pillar as fluorine and niobium sources,and the effect of seed layer prepared by hot dip-coating method and layer by layer(LBL)method were investigated.The KAUST-7 membrane with higher separation performance was fabricated by LBL seed method,which showed a H_(2)permeance of 2.23×10^(-7)mol/(m^(-2)•s•Pa)and achieved the ideal selectivities up to 24.86,17.34 and 12.95 for H_(2)/CO_(2),H_(2)/N_(2)and H_(2)/CH_(4),respectively.The substitution of concentrated HF with pre-synthesized NiNbOF_(5) inorganic pillar center avoids the hydrofluoric acid corrosion toα-Al_(2)O_(3)supports by one-pot synthesis,which contributed to the fabrication of gas-separation membrane under mild conditions.