Triggered Gate Opening and Breathing Effects during Selective CO₂ Adsorption by Merlinoite Zeolite

Abstract

Contents S1. Synthesis and Initial Characterisation S2. Crystallographic details of the refined hydrated Na-, (K-and K, Hand nd Cs-MER S3. Structural response to dehydration S4. Adsorption studies S5. In situ laboratory PXRD of M-MER with adsorbed CO2 S6. Crystallographic details of the refined dehydrated solids with adsorbed CO2 S7. CO2/CH4 separation and breakthrough curves S8. Kinetic measurements using the Zero Length Column technique S9. K,H-MER zeolite structural and adsorption results S2 S1. Synthesis and Initial Characterisation Synthesis Colloidal silica, Ludox HS-40 (12.5 g; 40%, suspension in water; Sigma-Aldrich) was added to 35% aqueous solution of tetraethylammonium hydroxide (3.15 g; 35% TEOAH, Sigma-Aldrich) and the resulting mixture was stirred for 1 h. To this mixture, a solution made by dissolving metal Al (0.8 g, 99%, Alfa Aesar) in 3 g TEAOH and KOH (0.6 g, 85%, Fisher Chemicals), which was also mixed for 1 h, was added. The gel formed was continuously stirred for 10 min, transferred to a PTFE-lined stainless-steel autoclave and hydrothermally treated at 423 K under slow rotation (60 rpm). The resultant solid product, collected after 96 h, was

The zero length column technique to measure adsorption equilibrium and kinetics: lessons learnt from 30 years of experience

“…In most cases structural modifications are triggered by a specific adsorbate concentration, but cases of temperature and pressure induced transitions have also been reported . Structural changes can manifest in number of ways including change of the cage volume, breathing (Barthelet et al 2002) and gate opening (Lozinska et al 2012;Georgieva et al 2019). The possibility of triggering a controlled change in the kinetic and/or equilibrium selectivity opens a range of unexplored opportunities both from the materials and processes point of view.…”

Synthesis of Discrete CHA Zeolite Nanocrystals without Organic Templates for Selective CO2 Capture

“…By blocking the pore entries, the extra‐framework cations selectively provide access for molecules to the zeolite channels and cages depending on the nature of the molecules [6] . A high selectivity towards CO 2 over CH 4 for small‐pore zeolites with RHO, MER, and CHA type framework has been observed, indicating that the cation gating effect permits the uptake of CO 2 but not CH 4 [7, 8] …”

The Origin of Selective Adsorption of CO2 on Merlinoite Zeolites

“…While merlinoite is rarely found in nature, several synthetic analogues like K‐M and Linde W have been reported and typically characterized with the Si/Al ratio range of 1.5–2.4 [8] . Wright and co‐workers have recently reported that CO 2 adsorption mechanism on the Na + , K + , and Cs + forms of an MER zeolite with Si/Al=3.8 synthesized using tetraethylammonium (TEA + ) ions as an organic structure‐directing agent (SDA), together with K + , is based on the breathing effect [7b] …”