Zeolite adsorbent-MOF layered nanovalves for CH4 storage

Abstract

Herein we demonstrate the use of metal organic framework layers coated on zeolite 5A adsorbent as effective nano-valves for CH4 storage at low storage pressure. The resultant nanovalved materials are capable of sealing high pressure CH4 inside the adsorbents and storing it at low pressure. Four different metal organic frameworks (MOF) were grown on 5A zeolite beads, and functioned as nanovalves. These MOFs included HKUST-1, Al-MOF, Ga-MOF, and Co-MOF. Ethanol, a cheap, renewable, and safe chemical, was employed as the nanovalve sealing molecule. It was found that the 2-crystallization step MOFs displayed the best performance regardless of the MOF coordinating metal. The methane storage capacity followed the order: Al-MOF > Ga-MOF > Co-MOF > Cu-MOF. The best performing material, 2-crystallization step Al-MOF, was able to store 33.6 (L (STP) CH4/L nanovalve adsorbent) excess CH4, corresponding to 46 % of the CH4 saturation capacity of the zeolite 5A bead adsorbent at <1 bar.