c7ta03244g
Highly permeable zeolite imidazolate framework composite membranes fabricated via a chelation-assisted interfacial reaction
Polyacrylonitrile (PAN) UF membranes (MWCO: 200 kDa) were purchased from Beijing Ande Technology Corporation (China). Sodium hydroxide (NaOH), sodium chloride (NaCl), and magnesium chloride (MgCl2) were supplied from Beijing Chemical Works (China). Methyl blue (MB), Congo red (CR), acid fuchsin (AF), magnesium sulfate (MgSO4), and sodium sulfate (Na2SO4) were obtained from Tianjin Guangfu Fine Chemical Institute (China) and used for the NF performance test. The precursors of ZIF-8, including zinc nitrate hexahydrate (Zn(NO3)2*6H2O) and 2-methylimidazole (Hmim, 99.5%), were purchased from Aladdin Industrial Corporation (China). Polyethyleneimine (PEI, Mw: 750000 Da) was supplied by TCI Chemicals (Japan). Bovine serum albumin (BSA, Mw: 67000 g mol-1) and humic acid (HA) were purchased from Beijing Aobox Biotechnology (China) and Macklin Inc. (China), respectively. Ultrapure water was produced by a lab water purification system (HYP-QX, China). All the chemicals and materials were used as received. 

The preparation process of the ZIF-8/PEI-HPAN composite membrane is illustrated in Scheme 2, in which the structure of ZIF-8 has been cited from the literature.29 To obtain a negatively charged surface, the PAN substrate was first hydrolyzed in an NaOH aqueous solution (2 mol L-1) at 65 degC for 60 min, followed by rinsing with DI-water (step 1).30 Then, the hydrolyzed PAN (HPAN) substrate was soaked in a 0.2-0.6 mol L-1 Zn(NO3)2 aqueous solution for 5 h at 25 +- 1 degC to coordinate Zn2+ on the HPAN substrate surface (step 2).16,22 Next, the membrane was introduced into a mixed PEI-Zn(II) complex solution containing 0.1-0.3 mol L-1 zinc nitrate and 0.4 wt% PEI aqueous solution for 0.5 h at a constant temperature (20-50 degC, step 3). After this, the residual aqueous solution was poured off, and the residual water droplets on the membrane surface were gently wiped off using a filter paper. Finally, the PEI-Zn(II)-saturated membrane was immersed in a 0.20 mol L-1 Hmim in a hexane solution for 5-20 min at 25 +- 2 degC to synthesize ZIF-8 crystals in situ (step 4).14 The obtained membrane was then rinsed three times with ethanol and dried at room temperature (25 +- 2 degC) for 2 h before further use.
Polyacrylonitrile (PAN) UF membranes
MWCO
200 kDa
kDa
2-methylimidazole (Hmim
99.5%
%
Polyethyleneimine (PEI
Mw
750000 Da
Da
Bovine serum albumin (BSA
Mw
67000 g mol-1
g mol-1
aqueous solution
NaOH
2 mol L-1
mol L-1
PAN substrate
hydrolyzed
65 degC
degC
PAN substrate
hydrolyzed
60 min
min
aqueous solution
Zn(NO3)2
0.2-0.6 mol L-1
mol L-1
hydrolyzed PAN (HPAN) substrate
soaked
5 h
h
hydrolyzed PAN (HPAN) substrate
soaked
25 +- 1 degC
degC
mixed PEI-Zn(II) complex solution
zinc nitrate
0.1-0.3 mol L-1
mol L-1
PEI-Zn(II) complex solution
PEI aqueous solution
0.4 wt%
wt%
membrane
introduced into a mixed PEI-Zn(II) complex solution
0.5 h
h
membrane
introduced into a mixed PEI-Zn(II) complex solution
20-50 degC
degC
Hmim
0.20 mol L-1
mol L-1
PEI-Zn(II)-saturated membrane
immersed
5-20 min
min
PEI-Zn(II)-saturated membrane
immersed
25 +- 2 degC
degC
obtained membrane
dried at room temperature
25 +- 2 degC
degC
obtained membrane
dried
2 h
h