Water Vapor Stability Enhancement Strategy Of Mofs And Their Adsorption And Separation Performance For C1/C2/C3 And CO₂

Improving energy efficiency and reducing carbon emissions are of the basic strategic principles and one of the effective measures in the face of global energy shortage crisis and climate issue.Mental-organic frameworks material is a highly efficient adsorbent,while some MOFs suffer from water vapor instability and easily damaged crystallinity structure.This work investigated the water vapor stability of NOT-401,Cu-BTC and ACN@Cu-BTCs and their water vapor stability enhancing strategy.Meanwhile,the adsorption and separation performances of C1/C2/C3 and CO₂ on these adsorbent materials were investigated.Enhancing the water vapor stability of MOFs under the premise of maintaining the adsorption properties of pristine materials,has practical significance and value for its industrial application.1)NOTT-401 was prepared and the water vapor stability of and its adsorption and separation performance for C1/C2/C3 were studied.The result shows that NOTT-401 is a high kinetic stable MOFs that could remain stable under humid conditions of 55%RH for more than10 days.This stability could be acscribe to the inert Sc metal center and the full coordination.It prevents water molecular from ourring hydrolysis.NOTT-401 exhibits excellent adsorption and separation capacities for CH₄,C₂H₆ and C₃H₈,which reached 0.66,4.35 and 4.84 mmol/g,respectively.And its selectivity for C₃H₈/CH₄ and C₂H₆/CH₄ were 61.6 and 10.3,which could be apply for C1/C2/C3 separation at ambient temperature and pressure.2)ACN@Cu-BTCs were synthesized by post-synthetic modification.The experimental results show that ACN@Cu-BTCs could not only maintain the crystallinity and the morphology,but more than 82%of BET specific area of pristine Cu-BTC was retained.The FT-IR spectra confirms ACN was grafted on the unsaturated Cu metal sites via Cu-N bonding.Meanwhile,ACN@Cu-BTCs exhibit decent thermal stability that can remain stable below 390 K.3)ACN@Cu-BTCs exhibit enhanced water vapor stability and moderate CO₂/CH₄adsorption separation performance comparing with Cu-BTC.After 20 days exposure to humidity at a relative humidity of 55%,Cu-BTC almost lost its CO₂ adsorption capacity,while ACN_1/1@Cu-BTC manage to reserved 100%of the their initial adsorption capacity of 3.54mmol/g.The enhanced stability of Cu-BTC was ascribe to steric effect and the hydrophobic environment around the Cu-unsaturated sites constructed by acetonitrile.It prevents water molecules from forming water clusters around the Cu site and occurring hydrolysis reactions.The IAST calculation results show that ACN_1/3@Cu-BTC well inherits the adsorption and separation performance of Cu-BTC for CO₂/CH₄,which was in the range of 4.1⁶.6.