Growth of ZnO self-converted 2D nanosheet zeolitic imidazolate framework membranes by an ammonia-assisted strategy

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.