New Azo-DMOF-1 MOF as a Photoresponsive Low-Energy CO₂ Adsorbent and Its Exceptional CO₂/N₂ Separation Performance in Mixed Matrix Membranes

Abstract

A new generation-2 light-responsive metal-organic framework (MOF) has been successfully synthesized using Zn as the metal source and both 2-phenyldiazenyl terephthalic acid and 1,4-diazabicyclo[2.2.2]octane (DABCO) as the ligands. It was found that Zn-azo-dabco MOF (Azo-DMOF-1) exhibited a photoresponsive CO adsorption both in static and dynamic condition because of the presence of azobenzene functionalities from the ligand. Further application of this MOF was evaluated by incorporating it as a filler in a mixed matrix membrane for CO/N gas separation. Matrimid and polymer of intrinsic microporosity-1 (PIM-1) were used as the polymer matrix. It was found that Azo-DMOF-1 could enhance both the CO permeability and selectivity of the pristine polymer. In particular, the Azo-DMOF-1-PIM-1 composite membranes have shown a promising performance that surpassed the 2008 Robeson Upper Bound.

An insight into the effect of azobenzene functionalities studied in UiO-66 frameworks for low energy CO2 capture and CO2/N2 membrane separation

“…For in situ measurement using UV-light, various control experiments had also been previously conducted to ensure that the heat generated from the UV light is negligible and does not signicantly affect the measurement result. 15,22,23 Mixed matrix membrane fabrication…”

“…The complete set-up for the gas separation rig used in this study has been described previously. 23 The membranes were rstly cut into a 2 cm in diameter coupon. These membranes were then mounted onto an aluminum washer and glued the surroundings with epoxy glue to seal the membranes.…”

“…This is based on our previous studies showing the advantage of having azobenzene functionalities to improve the CO 2 /N 2 separation performance in mixed matrix membranes. 15,23 We then chose PIM-1 as the polymer matrix considering its promising performance to surpass the 2008 Robeson upper bound. 39 All the MMMs were rstly characterized using PXRD, FTIR and SEM.…”

Molecularly engineered switchable photo-responsive membrane in gas separation for environmental protection

“…For instance, surface energy is the driving force of the surface responsive reorientation as systems fundamentally minimise the interfacial energy between the surface of the responsive material and its immediate environment. Numerous researches were reported by utilising MOF [24,37] and membranes [38,39] for the purpose of gas separation, focusing on the interfacial energy between the responsive material and its immediate environment to control the pore's opening of the separation system to the specific size of gas molecule. Since many gas mixtures to be separated are similar in size, common sieving mechanisms cannot efficiently cater to the specific size of gases.…”

“…The first generation of MOF is loaded with photo-responsive guest molecules, lending them an extrinsic photo-responsive property [32,39]. However, this approach is not applicable in all cases as the isomerisation of the guest molecule can be blocked by the host framework [35,50].…”