Intrinsically Microporous Polymer Nanosheets for High‐Performance Gas Separation Membranes

Abstract

Microporous polymer nanosheets with thicknesses in the range 3–5 nm and with high apparent surface area (Brunauer–Emmett–Teller surface area 940 m2 g−1) are formed when the effectively bifunctional (tetrafluoro) monomer used in the preparation of the prototypical polymer of intrinsic microporosity PIM‐1 is replaced with an effectively tetrafunctional (octafluoro) monomer to give a tightly crosslinked network structure. When employed as a filler in mixed‐matrix membranes based on PIM‐1, a low loading of 0.5 wt% network‐PIM‐1 nanosheets gives rise to enhanced CO2 permeability and CO2/CH4 selectivity, compared to pure PIM‐1.

Mitigation of Physical Aging with Mixed Matrix Membranes Based on Cross-Linked PIM-1 Fillers and PIM-1

“…Many small structures are visible, along with some ribbon-like features that may arise from agglomeration of smaller species. This is in marked contrast to the high cross-link density network-PIM-1 previously reported, 34 which showed nanosheets with thicknesses in the range 3−5 nm and lateral dimensions of a few hundred nanometers. For the LCD-network-PIM-1, height profiles are shown in Figure 4(c) along lines passing through some of the small particles, indicated as lines 1−4 in Figure 4(b).…”

“…Mixed gas permeability measurements were carried out using a binary feed mixture (25 mL min −1 of each gas) in a permeation apparatus based on the standard variable volume method, as reported previously. 34 The feed side pressure was kept constant at approximately 3 bar and 25 °C and the permeate side was at atmospheric pressure. Pieces of prepared freestanding membranes were masked between two aluminum-tape donuts, and the membrane−aluminum interface was sealed using twopart potting epoxy (Araldite Rapid, Industrial MTCE Suppliers).…”

“…In the pursuit of a porous organic filler which could potentially offer maximum compatibility with PIM-1, we recently introduced a tightly cross-linked version of PIM-1 (network-PIM-1) 34 for application in PIM-1-based MMMs. This utilized the effectively tetrafunctional monomer dicyanooctafluoro biphenyl (DCOB), instead of the effectively bifunctional monomer TFTPN, in a step-growth polymerization with TTSBI.…”

Boosting gas separation performance and suppressing the physical aging of polymers of intrinsic microporosity (PIM-1) by nanomaterial blending

“…The group also [200] used a highly crosslinked nanosheet form of network-PIM-1 as the filler in a more linear PIM-1. The authors demonstrated that the network-PIM-1 nanosheets (ABET = 940 m 2 ·g -1 ), produced by using tetra-functional (octafluoro) monomer instead of the typical bi-functional (tetrafluoro) monomer, when incorporated into PIM-1 (Mw = 158,000 g·mol -1 ; Đ = 3.0, ABET = 780 m 2 ·g -1 ) positively changed the membrane performance.…”

Superglassy Polymers to Treat Natural Gas by Hybrid Membrane/Amine Processes: Can Fillers Help?

“…Mixing superglassy polymers with porous and non-porous fillers has proven an attractive route to overcome the physical aging. Freestanding mixed matrix membranes (MMMs) have been successfully fabricated with metal organic framework (MOFs) [ 20 , 21 ], zeolites [ 22 ], silica [ 23 ], graphene-based materials [ 24 , 25 ], porous aromatic frameworks (PAFs) [ 26 , 27 ], and hypercrosslinked polymers (HCPs) [ 28 , 29 , 30 , 31 ]. The feasibility of using superglassy polymers in the hybrid membrane/amine process mainly depends on the long-term performance of the polymers under industrial operating condition, when produced as thin films to maximize CO 2 permeance.…”