摘要
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.
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.
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.
