Subfreezing conversion of ALD-derived ZnO layer to ultra-thin ZIF-8 membrane for high-flux C3H6 production

Abstract

ZIF-8 membrane is well-recognized for its capability in separating C3H6 from C3H6/C3H8 gas mixture. However, the low C3H6 permeance and inferior pressure resistance severely hinder its high-flux C3H6 production. In this study, ultra-thin and well-intergrown ZIF-8 membrane was fabricated through in situ subfreezing conversion of 10-cycle ALD-derived ZnO layer. Benefiting from the deposited 2 nm-thick ZnO layer and the inhibited ZIF-8 grain growth during subfreezing synthesis, the thickness of obtained ZIF-8 membrane was down to 180 nm, indicating low gas diffusion resistance; moreover, owing to well-intergrown grain boundary structure and slightly penetrated membrane layer, obtained ZIF-8 membrane was featured with enhanced pressure resistance. The ultra-thin thickness and strengthened structure endowed our membrane with unprecedented C3H6 flux (5.29 × 10−2 mol m−2 s−1) and decent C3H6/C3H8 separation factor (60.5) at feed pressure up to 7 bar, which was 1–2 orders of magnitude higher than state-of-the-art ZIF-8-based membranes and far beyond their performance limits under comparable conditions, rendering it a superb choice for high-yield C3H6 production.