posted on 2024-02-19, 13:03authored byTaliehsadat Alebrahim, Liang Huang, Heshali K. Welgama, Narjes Esmaeili, Erda Deng, Shiwang Cheng, Durga Acharya, Cara M. Doherty, Anita J. Hill, Clayton Rumsey, Martin Trebbin, Timothy R. Cook, Haiqing Lin
Mixed matrix materials (MMMs) containing
metal–organic framework
(MOF) nanoparticles are attractive for membrane carbon capture. Particularly,
adding <5 mass % MOFs in polymers dramatically increased gas permeability,
far surpassing the Maxwell model’s prediction. However, no
sound mechanisms have been offered to explain this unusual low-loading
phenomenon. Herein, we design an ideal series of MMMs containing polyethers
(one of the leading polymers for CO2/N2 separation)
and discrete metal–organic polyhedra (MOPs) with cage sizes
of 2–5 nm. Adding 3 mass % MOP-3 in a polyether increases the
CO2 permeability by 100% from 510 to 1000 Barrer at 35
°C because of the increased gas diffusivity. No discernible changes
in typical physical properties governing gas transport properties
are detected, such as glass transition temperature, fractional free
volume, d-spacing, etc. We hypothesize that this
behavior is attributed to fractal-like networks formed by highly porous
MOPs, and for the first time, we validate this hypothesis using small-angle
X-ray scattering analysis.