Two-dimensional nanosheet membranes with responsive nanochannels are appealing for controlled mass transfer/separation,but limited by everchanging thicknesses arising from unstable interfaces.Herein,an interfacially s...Two-dimensional nanosheet membranes with responsive nanochannels are appealing for controlled mass transfer/separation,but limited by everchanging thicknesses arising from unstable interfaces.Herein,an interfacially stable,thermo-responsive nanosheet membrane is assembled from twin-chain stabilized metal-organic framework(MOF)nanosheets,which function via two cyclic amide-bearing polymers,thermo-responsive poly(N-vinyl caprolactam)(PVCL)for adjusting channel size,and non-responsive polyvinylpyrrolidone for supporting constant interlayer distance.Owing to the microporosity of MOF nanosheets and controllable interface wettability,the hybrid membrane demonstrates both superior separation performance and stable thermo-responsiveness.Scattering and correlation spectroscopic analyses further corroborate the respective roles of the two polymers and reveal the microenvironment changes of nanochannels are motivated by the dehydration of PVCL chains.展开更多
Shaping crystalline porous materials such as metal organic frameworks （MOFs） and zeolites into two-dimensional （2D） nanosheet forms is highly desirable for developing high-performance molecular sieving membranes. ...Shaping crystalline porous materials such as metal organic frameworks （MOFs） and zeolites into two-dimensional （2D） nanosheet forms is highly desirable for developing high-performance molecular sieving membranes. However, conventional exfoliation-deposition is complex and challenging for the large-scale fabrication of nanosheet MOF tubular membranes. Here, for the first time, we report a direct growth technique by ZnO self-conversion and ammonia assistance to fabricate zeolitic imidazolate framework （ZIF） membranes consisting of 2D nanosheets on porous hollow fiber substrates; the membranes are suitable for large-scale industrial gas separation processes. The proposed fabrication process for ZIF nanosheet membranes is based on the localized self-conversion of a pre-deposited thin layer of ZnO in a ligand solution containing ammonium hydroxide as a modulator. The resulting ZIF 2D nanosheet tubular membrane is highly oriented and only 50 nm in thickness. It exhibits excellent molecular sieving performance, with high H2 permeance and selectivity for H2/CO2 separation. This technique shows great promise in MOF nanosheet membrane fabrication for large-scale molecular sieving applications.展开更多
基金support from the National Natural Science Foundation of China(Nos.21991123,51733003,21674025,and 51873035)“Qimingxing”project(No.19QA1400200)of the Shanghai Committee of Science and Technology.
文摘Two-dimensional nanosheet membranes with responsive nanochannels are appealing for controlled mass transfer/separation,but limited by everchanging thicknesses arising from unstable interfaces.Herein,an interfacially stable,thermo-responsive nanosheet membrane is assembled from twin-chain stabilized metal-organic framework(MOF)nanosheets,which function via two cyclic amide-bearing polymers,thermo-responsive poly(N-vinyl caprolactam)(PVCL)for adjusting channel size,and non-responsive polyvinylpyrrolidone for supporting constant interlayer distance.Owing to the microporosity of MOF nanosheets and controllable interface wettability,the hybrid membrane demonstrates both superior separation performance and stable thermo-responsiveness.Scattering and correlation spectroscopic analyses further corroborate the respective roles of the two polymers and reveal the microenvironment changes of nanochannels are motivated by the dehydration of PVCL chains.
基金This work was supported by the National Natural Science Foundation of China （Nos. 21476039 and 21076030）. M. T. thanks the Marie S~odowska-Curie Individual Fellowship for a postdoctoral grant. A. J. H. and O. K. F. gratefully acknowledge funding from the U.S. Dept. of F.nerg~ Office of Science, Basic Energy Sciences Program （No. DE-FG02-08ER15967）. The authors also thank Professor Huanting Wang from Monash University for further revising the manuscript.
文摘Shaping crystalline porous materials such as metal organic frameworks （MOFs） and zeolites into two-dimensional （2D） nanosheet forms is highly desirable for developing high-performance molecular sieving membranes. However, conventional exfoliation-deposition is complex and challenging for the large-scale fabrication of nanosheet MOF tubular membranes. Here, for the first time, we report a direct growth technique by ZnO self-conversion and ammonia assistance to fabricate zeolitic imidazolate framework （ZIF） membranes consisting of 2D nanosheets on porous hollow fiber substrates; the membranes are suitable for large-scale industrial gas separation processes. The proposed fabrication process for ZIF nanosheet membranes is based on the localized self-conversion of a pre-deposited thin layer of ZnO in a ligand solution containing ammonium hydroxide as a modulator. The resulting ZIF 2D nanosheet tubular membrane is highly oriented and only 50 nm in thickness. It exhibits excellent molecular sieving performance, with high H2 permeance and selectivity for H2/CO2 separation. This technique shows great promise in MOF nanosheet membrane fabrication for large-scale molecular sieving applications.
