Negative electrostatic potentials in a Hofmann-type metal-organic framework for efficient acetylene separation

Abstract

AbstractEfficient adsorptive separation of acetylene (C2H2) from carbon dioxide (CO2) or ethylene (C2H4) is industrially important but challenging due to the identical dynamic diameter or the trace amount. Here we show an electrostatic potential compatible strategy in a nitroprusside-based Hofmann-type metal-organic framework, Cu(bpy)NP (NP = nitroprusside, bpy = 4,4’-bipyridine), for efficient C2H2separation. The intruding cyanide and nitrosyl groups in undulating one-dimensional channels induce negative electrostatic potentials for preferential C2H2recognition instead of open metal sites in traditional Hofmann-type MOFs. As a result, Cu(bpy)NP exhibits a 50/50 C2H2/CO2selectivity of 47.2, outperforming most rigid MOFs. The dynamic breakthrough experiment demonstrates a 99.9% purity C2H4productivity of 20.57 mmol g−1from C2H2/C2H4(1/99,v/v) gas-mixture. Meanwhile, C2H2can also be captured and recognized from ternary C2H2/CO2/C2H4(25/25/50,v/v/v) gas-mixture. Furthermore, computational studies and in-situ infrared spectroscopy reveal that the selective C2H2binding arises from the compatible pore electro-environment generated by the electron-rich N and O atoms from nitroprusside anions.