Melamine‐Doped Covalent Organic Framework Membranes for Enhanced Hydrogen Purification

Abstract

Covalent organic frameworks (COFs) are promising materials for membrane separation thanks to their adjustable topological structures and surface properties of nanopores. Herein, a melamine (Me)-doped COF membrane was fabricated by chemically doping the melamine monomer into TpPa COF, which is formed by the condensation reaction between the 1,3,5-triformylphloroglucinol (Tp) and p-phenylenediamine (Pa) monomers via interfacial polymerization. The introduction of melamine monomer allows altering both the pore structure and pore surface of the TpPa COF membrane, leading to enhanced hydrogen purification performance. Specifically, the separation factor of H 2 /CO 2 gas mixture by using the melamine doped TpPa COF (TpPaMe COF) membrane reaches 12.7, with a hydrogen permeance of 727 GPU, in sharp contrast to the relatively low separation factor and gas permeance of 7.5 and 618 GPU of the undoped TpPa membrane. Besides, the TpPaMe COF membrane shows good running stability, with H 2 /CO 2 separation performance well surpasses the Robeson 2008 upper bound.

Self-Standing Covalent Organic Framework Membranes for H2/CO2 Separation

“…It is worth mentioning that the permeance of CO2 was lower due to the strong interaction between CO2 and COF frameworks. [37] These results verify our previous conjecture that both self-standing COFMs have the potential to separate H2/CO2. Subsequently, the obtained COFMs were used to separate H2/CO2 mixture gas at room temperature (25 °C).…”

Self‐Standing Covalent Organic Framework Membranes for H2/CO2 Separation

“…Although the kinetic diameter of CO 2 is smaller than that of CH 4 , both membranes showed even higher H 2 /CO 2 selectivity, which indicates that the molecular sieving effect does not dominate the separation process. As reported previously, [41][42][43] this phenomenon can be explained by the synergistic effect of adsorption and diffusion of gas in the membranes instead. When the gas mixture passes through the two self-standing membranes, only CO 2 can be retained in the pore structure of the membranes while other small gas molecules will easily permeate through the framework since imine-based COFMs show a strong adsorption of CO 2 .…”

Design, Preparation, and High Intrinsic Proton Conductivity of Two Highly Stable Hydrazone-Linked Covalent Organic Frameworks

“…MOFs have been studied comparatively extensively as proton conductors at present, but their poor stability limits their further applications. As highly crystalline solid materials, COFs have received continuous and extensive attention in the fields of catalysis, , gas adsorption and separation, , desalination, , and energy storage and conversion − with their variable skeleton structure, high specific surface area and uniformly distributed pores, and outstanding chemical and thermal stability , since their appearance in 2005, but the research of proton conduction did not achieve a breakthrough until 2014 …”