Carboxylate-functionalized polymers
of intrinsic microporosity (PIMs) are promising materials for gas
separation application. However, highly carboxylate-functionalized
PIMs (HCPIMs) have not been reported owing to overlooked intermediate
products. Herein, we successfully prepared HCPIMs (∼92 mol
% of carboxylic acid group) through a prolonged alkaline hydrolysis
process (360 h). HCPIMs were found to be soluble in various organic
solvents, such as tetrahydrofuran and dimethyl sulfoxide, and then
free-standing HCPIM membranes could be prepared by the common solution
casting method. The HCPIM membranes were found to have smaller interchain
distances and higher CO2 affinity than original PIM-1 films.
For example, small gas molecules, such as carbon dioxide, were effectively
separated due to the enhanced diffusivity selectivity combined with
the smaller cavity size. Further, strong interactions between carbon
dioxide and the carboxylic acid groups increased solubility selectivity.
These synergetic effects endowed the HCPIM membrane with a selectivity
of 53.6 for CO2/N2 separation, the highest among
reported chemically modified PIMs.
Laser-induced graphene (LIG) typically exhibits a mesostructure with a small specific surface area, which is detrimental to the electrochemical performance of micro-supercapacitors (MSCs). Herein, 3D nanostructured LIGs patterned on fluorinated polyimides (fPIs) via a laser photothermal method are reported. During laser-induced graphitization, a highly microporous structure in the LIG develops. Consequently, the patterned LIG (LIG-fPI) exhibits a very large specific surface area (1126.0 m 2 g −1 ), thereby enhancing its electrochemical performance. Specifically, in an H 2 SO 4 aqueous electrolyte, the micropatterned electrode exhibits an exceptional areal capacitance of 110 mF cm −2 (determined by cyclic voltammetry), which is 27 times higher than that of a LIG based on commercial polyimides and at least 7 times higher than that of current state-of-the-art MSCs. Furthermore, mechanically stable and flexible LIG-fPI-MSCs with an organic gel polymer electrolyte (working potential = ∼3 V) show very high power and energy densities of 0.58 mW cm −2 and 0.01 mW h cm −2 , respectively. Thus, these LIGs are promising for application in high-performance MSCs for flexible microelectronics.
PIM-1-based carbon–sulfur composites, combining covalent bonds and physical confinement concepts, operate without the shuttle effect in room-temperature sodium–sulfur batteries.
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