1  

Nanoparticle-templated nanofiltration membranes for ultrahigh

performance desalination

Zhenyi Wang et al.

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Supplementary Methods

Materials

Zn(NO3)2ꞏ6H2O, 2-methylimidazole, trimesoyl chloride, anhydrous piperazine were

purchased from Sigma-Aldrich. Tris(hydroxymethyl)aminomethane and dopamine

hydrochloride were purchased from Alfa-Aesar. SWCNTs (diameter < 2 nm, length > 5 μm,

purity 95%) was purchased from XFNANO (Nanjing, China). CaCO3 nanoparticles in a

diameter of 100 nm were purchased from BOYU GAOKE (Beijing, China). Other chemicals

used in this work were all obtained from Sinophram Co. Ltd. (Beijing, China) and used

directly without further purification. PES microfiltration membrane with pore size of 0.45 μm

was provided by Yibo Co. Ltd. (Haining, Zhejiang province, China). AAO membrane with

pore size of 200 nm was obtained from Whatman Co..

Synthesis

Preparation of PD/ZIF-8 nanopartilcles. ZIF-8 nanoparticles were synthesized as follows:

Taking the synthesis of 150 nm ZIF-8 nanopartilcles as an example, 40 ml 0.1 M

Zn(NO3)2ꞏ6H2O methanol solution was rapidly poured into 40 ml 0.4 M 2-methylimidazole

methanol solution under stirring at 28C. Milky dispersion was then collected after 1 hour.

After centrifugation under 8000 rpm and washed by methanol for three times, ZIF-8

nanoparticles were collected and dispersed in methanol for store. The synthesis of ZIF-8

nanoparticles in different particle sizes were done by just changing the concentrations of

Zn(NO3)2ꞏ6H2O and 2-methylimidazole. The obtained particle size of ZIF-8 corresponding to

the concentrations of the two reactants are listed in Supplementary Table 2.

PD/ZIF-8 nanoparticles were synthesized as follows: ZIF-8 nanoparticles were firstly

dispersed in water/methanol (1:1) solution in a concentration of 5 mg ml-1. Then 50 mg

dopamine hydrochloride and 10 ml 0.1 M Tris-buffer (pH 8.5) were added into 100 ml ZIF-8

dispersion in order. After stirring at 28 C for 5 h, dark grey dispersion was obtained. After

centrifugation under 10000 rpm and washed by methanol for three times, PD/ZIF-8

nanoparticles were obtained and stored in methanol for use.

Preparation of PD/UiO-66 nanoparticles. UiO-66 nanoparticles were synthesized as

follows: 244 mg zirconium chloride (ZrCl4) and terephthalic acid (174.7 mg, 1.04 mmol)

were dissolved in 30 ml DMF by sonication respectively. Then, the two solutions were poured

into 100 mL Teflon-lined autocave. Afterwards, 1.8 ml glacial acetic acid was added into the

mixted solution. The Teflon-lined autocave was then placed in an oven and heated to 120 ºC

for 24 h. The product was collected after centrifugation under 8000 rpm and washed by

methol for 3~5 times. 50 mg dopamine hydrochloride and 10 ml 0.1 M Tris-buffer (pH 8.5)

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was then added into 100 ml 5 mg ml-1 UiO-66 dispersion. This solution was heated to 40 ºC

under stirring for 5 h. The obtained PD-coated UiO-66 (PD/UiO-66) nanoparticles were then

collected by centrifugation under 8000 rpm for 10 min and washed by methanol for 3 times.

Preparation of PD/ZIF-67 nanoparticles. ZIF-67 nanoparticles were synthesized as follows:

40 ml 0.1 M Co(NO3)2ꞏ6H2O methanol solution was rapidly poured into 40 ml 0.4 M

2-methylimidazole methanol solution under stirring at 28 C. Purple dispersion was then

collected after 1 h. After centrifugation under 8000 rpm and washed by methanol for three

times, ZIF-67 nanoparticles were collected and dispersed in methanol for store. PD/ZIF-67

nanoparticles were synthesized as follows: ZIF-67 nanoparticles were firstly dispersed in

water/methanol (1:1) solution in a concentration of 5 mg ml-1. Then 50 mg dopamine

hydrochloride and 10 ml 0.1 M Tris-buffer (pH 8.5) were added into 100 ml ZIF-67

dispersion. After stirring at 28C for 5 h, dark purple dispersion was obtained. After

centrifugation under 10000 rpm and washed by methanol for three times, PD/ZIF-67

nanoparticles were obtained and stored in methanol for use.

Preparation of PD/CaCO3 nanoparticles. 0.5 g commercial CaCO3 nanoparticles was added

into 100 ml deionized water to get a milky dispersion under 30 W ultrasonic probe for 4 h. 50

mg dopamine was added into the above CaCO3 dispersion and stirring at 28 C for 5 h.

PD/CaCO3 nanoparticles were obtained after centrifugation under 8000 rpm for 10 min and

washed by water for 3 times.

4  

Supplementary Figure 1. TEM image of PD wrapped SWCNT. A thin PD layer with

thickness of ~2 nm is clearly observed (scale bar: 10 nm).

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Supplementary Figure 2. (a) Photograph and (b) AFM image of a cut-off SWCNTs film on

mica (scale bar: 2 μm). (c) TEM image of the SWCNTs film (scale bar: 100 nm). (d) XPS

survey spectrum and (e) corresponding C1s spectrum of SWCNTs film. Note: The SWCNTs

film was prepared by peeling it off from PES microfiltration membrane and transferred onto

mica. The thickness of SWCNTs film with bilayer is 152 ± 12 nm. Uniform network structure

with average pore size of 10-20 nm is clearly observed from TEM image. C1s XPS spectrum

shows the sp2 C at 284.6 eV ascribed to SWCNTs and three sp3 C peaks at 285.2 eV, 286.2

eV, and 288.2 eV originated from PA layer. The SWNCTs film was prepared by filtering 3 ml

PD/SWCNTs dispersion with concentration of 0.015-0.024 mg ml-1 onto a commercial PES

microfiltration membrane.

6  

Supplementary Figure 3. XRD spectra of pristine ZIF-8 nanoparticles and PD/ZIF-8

nanoparticles. The insert images are the TEM images of pristine ZIF-8 nanoparticles and

PD/ZIF-8 nanoparticles (scale bar: 100 nm).

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Supplementary Figure 4. Water contact angle on the surface of (a) SWCNTs/PES composite

membrane, (b) PD/ZIF-8 nanoparticles loaded SWCNTs/PES composite membrane, and (c)

uncoated ZIF-8 nanoparticles loaded SWCNTs/PES composite membrane.

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Supplementary Figure 5. SEM images of (a) ZIF-8 nanoparticles loaded SWCNTs/PES

composite membrane (scale bar: 1 μm) and (b) PD/ZIF-8 nanoparticles loaded SWCNTs/PES

composite membrane (scale bar: 1 μm).

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Supplementary Figure 6. SEM images of ZIF-8 nanoparticles loaded SWCNTs/PES

composite membrane after interfacial polymerization reaction (a) and then immersed in water

in (b) 10 min, (c) 40 min, and (d) 60 min. The loading mass of ZIF-8 nanoparticles is 4.3

μg cm-2. The scale bar of images is 1 μm.

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Supplementary Table 1. Desalination performance of PA NF membranes prepared from

ZIF-8 nanoparticles loaded SWCNTs/PES composite membrane and PD/ZIF-8 nanoparticles

loaded SWCNTs/PES composite membrane, respectively. The feed solution is 1000 ppm

Na2SO4. The applied pressure for filtration is 4 bar.

Membrane Permeating flux (Lm-2h-1) Rejection (%)

with ZIF-8 245 72

with PD/ZIF-8 214 95

Note: As for the function of PD layer in the PD/ZIF-8 nanoparticles, it is mainly used to

improve the hydrophilicity of ZIF-8 nanoparticles (Supplementary Figure 4). Pure ZIF-8 is

hydrophobic. It is prone to cause the de-wetting of PIP solution and generate defects on PA

layer. To confirm it, a control experiment was done where ZIF-8 nanoparticles without PD

coating were deposited on the surface of SWCNTs/PES composite membrane for interfacial

polymerization. As shown in Supplementary Figure 5, ZIF-8 nanoparticles without PD

coating are easy to form larger aggregates on SWCNTs/PES composite membrane

(Supplementary Figure 5a) in comparison with PD/ZIF-8 nanoparticles (Supplementary

Figure 5b). After interfacial polymerization, ZIF-8 nanoparticles could be gradually dissolved

too and create a crumpled PA layer (Supplementary Figure 6) after immersed in water.

However, the obtained PA NF membrane exhibits a low rejection to Na2SO4 (72%), which is

much lower than the PA NF membrane prepared from PD/ZIF-8 nanoparticles loaded

SWCNTs/PES membrane (Supplementary Table 1).

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Supplementary Figure 7. SEM images of PD/ZIF-8 nanoparticles loaded SWCNTs/PES

composite membrane with interfacial polymerization time of (a) 30 s, (b) 1 min, and (c) 5 min

(Scale bar: 1 μm). Note: As shown in Supplementary Figure 7, the stability of ZIF-8

nanoparticles with the increase of interfacial polymerization time was investigated. When the

polymerization increases to 1 min, the PD/ZIF-8 nanoparticles are clearly observed. When the

polymerization increases to 5 min, the profile of the PD/ZIF-8 still can be seen although they

are covered by a thicker PA layer. It is expected that more HCl will be generated during

interfacial polymerization with increasing the polymerization time. This result indicates that

PD/ZIF-8 nanoparticles are stable during interfacial polymerization process and the generated

HCl during interfacial polymerization has little contribution to the dissolution of PD/ZIF-8

nanoparticles.

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Supplementary Figure 8. SEM images of (a) PD/ZIF-8 nanoparticles loaded SWCNTs/PES

composite membrane and the membrane after immersed in water for 1 minute (b), 5 minutes

(c), and 10 minutes (d). The scale bar of images is 1 μm.

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Supplementary Figure 9. SEM images of PD/ZIF-8 nanoparticles loaded SWCNTs/PES

composite membrane (a) and the membrane after immersed in 1 M Hmim aqueous solution

for 1 h (b) and 5 h (c). SEM images of PD/ZIF-8 nanoparticles loaded SWCNTs/PES

composite membrane (d) and the membrane after immersed in alkaline solution (pH = 13) for

1 h (e) and 5 h (f). The scale bar of images is 500 nm.

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Supplementary Figure 10. Morphology change of PD/ZIF-8 nanoparticles beneath PA layer

as immersing in Hmim ligand solution for (a) 0 min, (b) 1 h and (c) 5 h after interfacial

polymerization. The scale bar of images is 500 nm.

Note. As for the dissolution mechanism of ZIF-8 nanoparticles in water, it has been recently

proved by Lin, et al. (see Ref. 31). It is proposed that there is a dynamic equilibrium between

generation process and hydrolysis process of ZIF-8. Such a dynamic equilibrium obeys the

following reaction equation:

where [Zn(mim)2]n is ZIF-8 nanoparticles, Hmim is the ligand of 2-methylimidazole. In their

work, they found that a ZIF-8 composed membrane can dissolve in water when the mass ratio

of ZIF-8 to water is around 0.0017:100. In our case, the mass ratio of ZIF-8 nanoparticles to

water is around 0.00025:100. Under such a low concentration, the dissolution of ZIF-8

nanoparticles could happen much easier. To further confirm such a dissolution mechanism,

the following control experiments are done where PD/ZIF-8 nanoparticles loaded

SWCNTs/PES composite membranes were immersed into pure water, water containing 1 M

Hmim and alkaline solution (pH: 13) respectively, for different time to observe whether the

loaded PD/ZIF-8 nanoparticles dissolve or not. As shown in Supplementary Figure 8, the

PD/ZIF-8 nanoparticles are quickly dissolved and totally disappeared after 10 min as

immersed the membrane in pure water. In comparison, the PD/ZIF-8 nanoparticles did not

dissolve at all in the other two cases even for a long immersing time up to 5 h (Supplementary

Figure 9). This is because the existence of either Hmim ligand or OH- in the immersion

solution could effectively suppress the hydrolysis of ZIF-8. In addition, to further prove the

suppression effect of the existence of Hmim ligand on the dissolution of ZIF-8 nanoparticles,

PD/ZIF-8 nanoparticles loaded SWCNTs/PES composite membrane after interfacial

polymerization was immersed in 1 M Hmim solution too. As shown in Supplementary Figure

10, no PD/ZIF-8 nanoparticles are dissolved until 5 h.

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Supplementary Figure 11. Top-view SEM image of PA NF membrane prepared from

SWCNT/PES composite membrane without PD/ZIF-8 nanoparticles loading. The scale bar of

(a) and (b) is 1 μm and 500 nm, respectively.

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Supplementary Figure 12. TEM image of residual PD fragments (scale bar: 50 nm).

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Supplementary Figure 13. SEM images of PD/ZIF-8 nanoparticles loaded SWCNTs/PES

composite membrane after removal of ZIF-8 nanoparticles (a) before and (b) after interfacial

polymerization. (c) is the enlarged image from (b). The scale bar in the images of (a) and (c)

is 500 nm and is 1 μm in the image of (b).

Note: As for the evolution of PD coating during polymerization, we think that there might be

some PD residuals between SWCNTs/PES composite membrane and PA layer after removal

of ZIF-8 nanoparticles. However, its effect on PA NF membrane is negligible based on the

following two control experiments:

(1) The PD/ZIF-8 nanoparticles was first dissolved in dilute HCl solution to remove all

ZIF-8. The residual PD was then collected for TEM observation. As shown in Supplementary

Figure 12, PD fragments in the width of 5-30 nm are observed. In combination of our TEM

image of PD/ZIF-8 nanoparticles (Supplementary Figure 3), it indicates that the content of PD

coating layer is extremely small in PD/ZIF-8 nanoparticles.

(2) To directly evaluate the impact of the residual PD on the PA layer, PD/ZIF-8

nanoparticles loaded SWCNTs/PES composite membrane was immersed into water for

sufficient time to remove the ZIF-8 nanoparticles completely and then interfacial

polymerization was conducted. As shown in Supplementary Figure 13a, some PD fragments

can be observed on SWCNTs/PES membrane after removal of inner ZIF-8 nanoparticles.

After interfacial polymerization on such a PD fragments loaded SWCNTs/PES membrane,

thin PA layer with smooth surface is obtained (Supplementary Figure 13b and 13c) and no

obvious crumple structures are observed. The PA NF membrane prepared from such a

residual PD loaded SWCNTs/PES membrane displays a permeating flux of 140 Lm-2h-1bar-1

and ~98% rejection to 1000 ppm Na2SO4. This value is similar with the PA NF membrane

prepared from the pristine SWCNTs/PES membrane, indicating the residual PD fragments has

little effect on PA NF membrane.

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Supplementary Figure 14. (a) Schematical illustration of cross-section structure of PA NF

membrane etched by FIB technique. (b) SEM image of groove etched by FIB with etched

depth of 2 μm (scale bar: 2 μm). (c) Enlarged cross-sectional SEM image of PA NF

membrane (scale bar: 500 nm). (d) and (e) Magnified SEM images showing the SWCNTs

layer plus PA layer and crumple structure (scale of both images is 100 nm). (f) is a diagram

corresponding to (e). Note: As for the thickness of crumpled PA layer, we try to evaluate it by

a focus ion beam-scanning electron microscope (FIB-SEM) technology. The results are

presented in Supplementary Figure 14. A typical structure of the cross-section of the

crumpled PA NF membrane produced by FIB is schematically shown in Supplementary

Figure 14a. A 300 nm thickness of Pt film was firstly deposited on the surface of PA NF

membrane to obtain a clear profile of membrane surface. Ion beam produced from gallium

was used to etch a rectangular groove with depth of 2 μm, then cross-section of NF membrane

was observed by rotating the sample stage in an angle of 53º. The corresponding scale bar in

the SEM image have been corrected according to the rotated angle. Supplementary Figure 14b

is the etched cross-sectional image of the PA NF membrane. The enlarged cross-sectional

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image shows clear deposied Pt layer with thickness of 300 nm (Supplementary Figure 14c).

Under Pt layer, a thin layer around ~80 nm could be clearly observed, which corresponds to

the sum of SWCNTs layer plus PA layer (Supplementary Figure 14d). The thickness of pure

SWCNTs layer is around 75 nm as has been confirmed by AFM (Supplementary Figure 2).

Therefore, the thickness of PA layer in this area is estimated to be as thin as in the several

nanometer scale. Luckily, a crumple structure with large rise and fall can be seen from

enlarged image (Supplementary Figure 14e). Several vesicae formed from crumpled PA layer

are clearly observed as marked by arrows. The thickness of PA layer as estimated from the

thickness of vesica wall is around 8-14 nm. This value is similar with the thickness of PA

layer prepared without PD/ZIF-8 nanoparticles as reported in our previous work (see Ref. 28).

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Supplementary Figure 15. Rejection curves to PEG with different molecular weight. Note:

As for the effective pore size, the molecular weight cut-off (MWCO) of PA NF membranes

prepared with and without PD/ZIF-8 nanoparticles loading was determined through

permeation tests to the PEG with different molecular weight. As shown in Supplementary

Figure 15, the MWCO for PA layer without PD/ZIF-8 is 400, which corresponds to an

effective pore radius of about 0.470 nm and the MWCO for PA layer with PD/ZIF-8 is 410,

which corresponds to an effective pore radius of about 0.477 nm. The difference of effective

pore radius between them is only 0.007 nm. In addition, the two PA layers exhibit same

rejection behaviors to PEG when the PEG molecular weight is larger than 400.

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Supplementary Figure 16. (a and b) C1s, (c and d) O1s, and (e and f) N1s XPS spectra of

PA NF membranes prepared without and with PD/ZIF-8 nanoparticles loading.

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Supplementary Figure 17. AFM images of PA NF membranes prepared from

SWCNTs/AAO composite support membrane with different PD/ZIF-8 nanoparticles loading

mass: (a) 0.9 μg cm-2, (b) 2.2 μg cm-2, (c) 4.3 μg cm-2, and (d) 6.4 μg cm-2. The scale bar of

images is 4 μm.

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Supplementary Figure 18. SEM images of ZIF-8 nanoparticles (up) and corresponding

PD/ZIF-8 nanoparticles (down) with size of (a and a1) 30 nm, (b and b1) 100 nm; (c and c1)

200 nm, and (d and d1) 400 nm. The scale bar of images is 200 nm.

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Supplementary Table 2. List of ZIF-8 particle size corresponding to the reactant

concentrations.

Size of ZIF-8 nanoparticles

(nm)

Concentration of reactants (M)

Zn(NO3)2ꞏ6H2O 2-methylimidazole

30 0.05 0.4

100 0.075 0.3

150 0.1 0.4

200 0.125 0.5

400 0.1 0.3

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Supplementary Figure 19. Impact of PD/ZIF-8 nanoparticle size on crumple structure.

SEM images of (a-f) PD/ZIF-8 nanoparticles loaded SWCNTs/PES composite membrane and

(a1-f1) corresponding PA NF membranes: (a and a1) without PD/ZIF-8 nanoparticles loading;

with PD/ZIF-8 nanoparticles loading: (b and b1) 30 nm; (c and c1) 100 nm, (d and d1) 150

nm, (e and e1)200 nm, and (f and f1) 400 nm. The scale bar of images is 500 nm.

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Supplementary Figure 20. Desalination performance of PA NF membrane prepared with

different size of PD/ZIF-8 nanoparticles.

Note: ZIF-8 nanoparticles with different sizes, 30 nm, 100 nm, 200 nm, and 400 nm are

also synthesized (Supplementary Table 2)and used to fabricate PA NF membrane with same

loadig mass. Supplementary Figure 18 shows the SEM images of ZIF-8 nanoparticles and

corresponding SEM images of PD/ZIF-8 nanoparticles with different sizes. These PD/ZIF-8

nanoparticles were loaded onto the SWCNTs/PES composite membranes for interfacial

polymerization, respectively. The results are shown in Supplementary Figure 19. It can be

seen that all of PD/ZIF-8 nanoparticles are successfully dissolved and crumpled PA layer are

achieved especially when the ZIF-8 nanoparticles larger than 30 nm. With the increase of

PD/ZIF-8 nanoparticle size, larger crumple structures are generated. The desalination

performance of the corresponding PA NF membranes are tested and the results are presented

in Supplementary Figure 20. The membrane permeating flux are 213, 200 and 214 Lm-2h-1

corresponding the ZIF-8 nanoparticle size of 30, 100 and 150 nm, respectively. Meanwhile,

the corresponding rejection to Na2SO4 is 95%, 96% and 95.3%, respectively. Further

increasing the nanoparticles size to 200 nm and 400 nm, the permeating flux of corresponding

PA NF membranes decrease to 157 and 171 Lm-2h-1 with rejection to Na2SO4 of 92% and

95.7%, respectively.

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Supplementary Figure 21. Variation of rejection with respect to different Na2SO4

concentration at applied pressure of 4 bar.

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Supplementary Figure 22. Summary of the filtration performance of the state-of-the-art NF

membranes reported in literature in consideration of permeance and rejection for MgSO4.

Note: The corresponding refences of cycle points of 1-8, 9, 10, 11 and 12-17 are Ref. 2-9, 11,

13, 14 and 16-21 listed in Supplementary References.

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Supplementary Figure 23. XRD spectra of pristine UiO-66 nanoparticles and

polydopamine-coated UiO-66 (PD/UiO-66) nanoparticles used in this work. The scale bar of

insert images is 50 nm). Note: It reveals that the crystal structure of the UiO-66 nanoparticles

was unaffected by the PD coating. The insert images are the TEM images of the two

nanoparticles correspondingly. The PD/UiO-66 nanoparticles have a diameter of 100-150 nm.

30  

Supplementary Figure 24. SEM images of (a) PD/UiO-66 nanoparticles loaded

SWCNTs/PES composite membrane with loading mass of 8.8 μg cm-2 and (b) corresponding

resulting PA NF membrane after interfacial polymerization reaction on it where the

membrane was immersed into water for more than 24 h before SEM characterization. The

scale bar of images is 1 μm.

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Supplementary Figure 25. Permeance and rejection of PA NF membranes prepared from

PD/UiO-66 nanoparticles loaded SWCNTs/PES composite membrane with different

PD/UiO-66 nanoparticles loading mass (Na2SO4 concentration: 1000 ppm; Applied pressure:

4 bar). Note: It shows that the change of membrane flux negatively correlates with the

PD/UiO-66 nanoparticles loading mass at low loading mass below 4 μg cm-2. After that, the

change of membrane flux positively correlates with the PD/UiO-66 nanoparticles loading

mass, correspondingly the salt rejection decrease slightly with the increase of loading mass.

With a PD/UiO-66 nanoparticles mass loading of 8.6 μg cm-2, the permeance reaches a

maximum of 36.7 Lm-2h-1bar-1 with the rejection of ~97%.

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Supplementary Figure 26. SEM images of PD/CaCO3 nanoparticles loaded SWCNTs/PES

composite membrane (a) before interfacial polymerization, (b) after interfacial polymerization

and (c) immersed into water for 24 h after interfacial polymerization. The scale bar of images

is 500 nm.

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Supplementary Figure 27. SEM images of PD/ZIF-67 nanoparticles loaded SWCNTs/PES

composite membrane (a) before interfacial polymerization, (b) after interfacial polymerization

and (c) immersed into water for 60 min after interfacial polymerization. The scale bar of

images is 500 nm.

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Supplementary Table 3. Permeating flux and rejection of PA NF membranes prepared from

PD/ZIF-67 and PD/CaCO3 nanoparticles loaded SWCNTs/PES composite membranes. Both

of the nanoparticle loading masses are 4.3 μg cm-2. The concentration of Na2SO4 is 1000 ppm.

The applied pressure is 4 bar.

Membrane Permeating flux (Lm-2h-1) Rejection (%)

without nanoparticles 131 ± 2 99.0 ± 0.5

with PD/ZIF-67 183 ± 9 97.2 ± 1.3

with PD/CaCO3 191 ± 4 96.5 ± 0.8

Note: Other kinds of nanoparticles those can be easily removed by mild post-treatment can be

used as sacrificial template too. To confirm this aspect, calcium carbonate (CaCO3)

nanoparticles (100 nm in diameter) and ZIF-67 nanoparticles (300-500 nm in diameter) were

chosen as sacrificial nanomaterials instead of ZIF-8 MOF nanoparticle. The resulting

morphologies of PA NF membranes are shown in Supplementary Figure 26 and

Supplementary Figure 27, respectively. It can been seen that the crumpled PA layers could be

also obtained after removing the pre-loaded PD/CaCO3 nanoparticles and PD/ZIF-67

nanoparticles.

The permeating flux and rejection of the two membranes were tested and given in

Supplementary Table 3 in comparison with the membranes without nanoparticles loading.

The permeating flux of the two membranes are 191 Lm-2h-1 for PD/CaCO3 nanoparticles

loading and 183 Lm-2h-1 for PD/ZIF-67 nanoparticles loading. These values are higher than

that of the membrane without nanoparticles loading (131 Lm-2h-1). These results indicate that

other soluble nanoparticles could also be used as sacrificial template to play the same role as

ZIF-8 nanoparticles.

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