Polyimides
for
natural
gas
separation
are
synthesized
from
copolycondensation
of
5-(1H-benzimidazol-2-yl)benzene-1,3-diamine
(BIB)
with
2,3,5,6-tetramethyl-1,4-phenylenediamine
(Durene)
and
4,4′-(hexafluoroisopropylidene)diphthalic
anhydride
(6FDA)
different
6FDA/BIB/Durene
ratios.
All
polyimides
containing
benzimidazole
groups
in
side
chains
display
good
processability,
outstanding
thermal
stability,
excellent
mechanical
properties.
The
CO2
permeability
CO2/CH4
selectivity
the
change
ratio
or
BIB
content.
At
a
total
pressure
2
bar
feed
50:50,
polyimide
30%
content
(F10B3D7)
exhibits
high
197.2
Barrer
coupled
38.6,
which
is
close
to
2008
Robeson's
upper
bound.
Besides,
CO2-induced
plasticization
physical
aging
membranes
can
also
be
regulated
by
tuning
ratio.
Specifically,
F10B3D7
resistance
stability
against
aging,
it
demonstrated
promising
candidate
purification
biogas
removal
molecules
gas.
ACS Applied Materials & Interfaces,
Год журнала:
2025,
Номер
unknown
Опубликована: Янв. 30, 2025
Polyimide
(PI)-based
gas
separation
membranes
are
of
great
interest
in
the
field
H2
purification
owing
to
their
good
thermal
stability,
chemical
and
mechanical
properties.
Among
polyimide-based
membranes,
intrinsically
microporous
polyimides
easily
soluble
common
organic
solvents,
showing
potential
for
fabricating
hollow
fiber
membranes.
However,
based
on
solution-diffusion
model,
improving
free
volume
or
movability
polymer
chains
can
improve
permeability,
but
would
result
poor
stability.
Herein,
we
develop
a
carbazole-alkyl-based
diamine
monomer
that
endows
PI
with
"rigid-soft"
structure
balance
trade-off
between
them.
Soft
units
enhance
during
film-forming
process,
ensuring
rigid
achieve
tight
chain
packing
strong
intermolecular
interactions.
Meanwhile,
bulky
carbazole
groups
could
further
restrict
motion
soft
solid
state.
On
one
hand,
it
restricts
below
Tg,
enhancing
small
selectivity
He.
other
ensures
Moreover,
extending
length
alkyl
helps
interactions
simultaneously,
thereby
optimizing
permeability/selectivity
trade-off.
As
result,
as-prepared
shows
permeability
89.61
Barrer,
H2/CH4
87.85,
H2/N2
45.03
contrast
reference
FPI
TFMB-6FDA
exhibiting
92.95
72.62,
38.57.
high
Tg
value
334
°C
is
also
achieved.
Abstract
The
practical
use
of
polymers
intrinsic
microporosity
(PIMs)
in
CO
2
separation
is
often
hindered
by
their
moderate
selectivity,
performance
instability
over
time,
and
pressure
constraints.
To
address
these
limitations,
a
straightforward
approach
presented
to
enhance
the
capability
PIM‐1
incorporating
metal
ions
into
uniformly
hydrolyzed
(cPIM).
This
dual
linking
strategy,
achieved
via
ionic
coordination
bonding
with
polymeric
side
chains
including
─COOH
─CONH
,
restructures
polymer,
disrupting
hydrogen
bonds
between
cPIM
creating
active
sites
for
π‐complexation.
modification
enhances
gas
permeability
while
maintaining
high
selectivity.
optimized
zinc‐coordinated
membrane
achieves
an
impressive
≈2,500
Barrer
/N
/CH
4
selectivities
27.1
23,
respectively,
outperforming
pristine
(700
Barrer;
=
27;
19).
Notably,
this
surpasses
2008
Robeson
upper‐bound
limits
both
pairs.
Additionally,
metal‐coordinated
membranes
exhibit
remarkable
long‐term
stability,
resisting
aging
effects
up
20
days
anti‐plasticization
properties
at
pressures
bar.
These
dual‐crosslinked
demonstrate
promising
potential
mixed
separation,
indicating
suitability
real‐world
industrial
applications.
