Reduced Aging in Carbon Molecular Sieve Membranes Derived from PIM-1 and MOP-18

Abstract

Carbon molecular sieve membranes (CMSMs) commonly lose permeability over time due to the collapse of micropores. This decline in permeability, due to the densification of the membrane, is known as physical aging. CMSMs derived from polymers of intrinsic microporosity (PIM-1) are highly affected by physical aging, with declines in permeability greater than 60% over time. It is hypothesized that the densification of CMSMs derived from this high-free-volume polymer precursor is thermodynamically driven by the collapse of large unconnected graphene domains to reach a more stable conformation (i.e., graphite). This study describes a novel strategy to mitigate physical aging by pillaring the CMSM using copper nanoparticles. Highly soluble metal−organic polyhedra-18 (MOP-18) was introduced into PIM-1 with loadings up to 40 wt/wt to form a mixed-matrix membrane (MMM). Pyrolysis of the MMM at 550 °C resulted in the in situ formation of copper metal nanoparticles that acted as pillars for the graphene sheets within the CMSM, preventing the collapse of the micropores, thus minimizing the aging of the CMSM. Single gas permeation measurements of CO 2 and CH 4 were made on the pristine polymer-derived CMSM and the copper-pillared CMSM at 35 °C and 2 bar to confirm the membranes' resistance to physical aging. The CH 4 permeability for the PIM-1 CMSM decreased by ∼60%, from 64 to 27 Barrers, over a period of 7 days, while the copper-pillared PIM-1 CMSM remarkably showed essentially no decline in CH 4 permeability. This research demonstrates a general approach to reducing physical aging in CMSMs.

Carbon fiber composite electrodes derived from metal organic polyhedra-18 and matrimid for hybrid supercapacitors

“…53 Metal–organic polyhedra (MOP) with long carbon chains attached to their outer shell are soluble in organic solvents and hence they can be utilized to disperse redox active metal nanoparticles. 54 Additionally, thermal decomposition of MOP structures creates porosity in the electrode enhancing the surface area and electrolyte accessibility after carbonization. Metal–organic polyhedra-18 (MOP-18) was used in this study as a PC precursor and to the best of our knowledge, this work presents the first hybrid supercapacitor based on a metal–organic polyhedra derived PC component.…”

Pillared Carbon Membranes Derived from Cardo Polymers

“…Crosslinking imparts polymer rigidity and plasticization-resistant properties with high permselectivity [ 30 , 31 , 32 , 33 , 34 , 35 , 36 ] and reduction in physical aging [ 37 , 38 , 39 , 40 ] but is limited to the availability of functional groups in the precursor. Nakagawa et al reported the control of micropores via pillaring in a carbonized ion exchange resin [ 41 ], and, more recently, pillaring of CMSMs from the pyrolysis of MOP-18/PIM-1 mixed matrix membranes (MMMs) was reported by Cosey et al [ 42 ]. In this study, copper nanoparticles were created from the pyrolysis of the soluble copper-based metal–organic polyhedra (MOP-18, Figure 1 b) dispersed in PIM-1.…”

Mitigated Aging in a Defective Metal–Organic Framework Pillared Polymer of an Intrinsic Porosity Hybrid Membrane for Efficient Gas Separation

“…Very recently, incorporating nanoparticles into the polymer was found to be an efficient way to pillar the pore structure and thus prevent the collapse of molecular sieve membranes. 29 Inspired by this concept, UiO-66 nanoparticles were synthesized to serve as pillars to mitigate the aging of PIMs. To increase the compatibility between the MOF particles and PIM-1, defective engineering was adopted to allow the exposed −OH part in the carboxyl group of defective UiO-66 connecting with cyano groups and the carbonyl part in the carboxyl group with bare methyl groups of PIM-1 chains, as schematically shown in Scheme 1.…”

“…Very recently, incorporating nanoparticles into the polymer was found to be an efficient way to pillar the pore structure and thus prevent the collapse of molecular sieve membranes . Inspired by this concept, UiO-66 nanoparticles were synthesized to serve as pillars to mitigate the aging of PIMs.…”