Porous polypropylene hollow fiber (PPHF) membranes are widely used in liquid purification. However

the hydrophobicity of polypropylene (PP) has limited its applications in water treatment. Herein

we demonstrate that

for the first time

atomic layer deposition (ALD) is an effective strategy to conveniently upgrade the filtration performances of PPHF membranes. The chemical and morphological changes of the deposited PPHF membranes are characterized by spectral

compositional

microscopic characterizations and protein adsorption measurements. Al

2

O

3

is distributed along the cross section of the PP hollow fibers

with decreasing concentration from the outer surface to the inner surface. The pore size of the outer surface can be easily turned by altering the ALD cycles. Interestingly

the hollow fibers become much more ductile after deposition as their elongation at break is increased more than six times after deposition with 100 cycles. The deposited membranes show simultaneously enhanced water permeance and retention after deposition with moderate ALD cycle numbers. For instance

after 50 ALD cycles a 17% increase in water permeance and one-

fold increase in BSA rejection are observed. Moreover

the PP membranes exhibit improved fouling-resistance after ALD deposition.