Bioinspired Gradient Covalent Organic Framework Membranes for Ultrafast and Asymmetric Solvent Transport.

Gradients play a pivotal role in membrane technologies, e.g., osmotic energy conversion, desalination, biomimetic actuation, selective separation, and more. In these applications, the compositional gradients are of great relevance for successful function implementation, ranging from solvent separation to smart devices; However, the construction of functional gradient in membranes is still challenging both in scale and directions. Inspired by the specific function-related, graded porous structures in glomerular filtration membranes, a general approach for constructing gradient covalent organic framework membranes (GCOMx) applying poly (ionic liquid)s (PILs) as template is reported here. With graded distribution of highly porous covalent organic framework (COF) crystals along the membrane, GCOMx exhibts an unprecedented asymmetric solvent transport when applying different membrane sides as the solvent feed surface during filtration, leading to a much-enhanced flux (10-18 times) of the "large-to-small" pore flow comparing to the reverse direction, verified by hydromechanical theoretical calculations. Upon systematic experiments, GCOMx achieves superior permeance in nonpolar (hexane ≈260.45 LMH bar-1) and polar (methanol ≈175.93 LMH bar-1) solvents, together with narrow molecular weight cut-off (MWCO, 472 g mol-1) and molecular weight retention onset (MWRO, <182 g mol-1). Interestingly, GCOMx shows significant filtration performance in simulated kidney dialysis, revealing great potential of GCOMx in bionic applications.

Carbon Nanotube Template-Assisted Synthesis of Conjugated Microporous Polytriphenylamine with High Porosity for Efficient Supercapacitive Energy Storage.

Engineering of conjugated microporous polymers (CMPs) with high porosity, redox activity, and electronic conductivity is of significant importance for their practical applications in electrochemical energy storage. Aminated-multiwall carbon nanotubes (NH2 -MWNT) are utilized to modulate the porosity and electronic conductivity of polytriphenylamine (PTPA), which is synthesized via Buchwald-Hartwig coupling reaction of tri(4-bromophenyl)amine and phenylenediamine as constitutional units in a one-step in situ polymerization process. Compared to PTPA, the specific surface area of core-shell PTPA@MWNTs has been greatly improved from 32 to 484 m2  g-1 . The PTPA@MWNTs exhibites an improved specific capacitance, with the highest value 410 F g-1 in 0.5 M H2 SO4 at a current of 10 A g-1 achieve for PTPA@MWNT-4 due to the hierarchical meso-micro pores, high redox-activity and electronic conductivity. Symmetric supercapacitor assemble by PTPA@MWNT-4 has a capacitance of 216 F g-1 of total electrode materials and retains 71% of initial capacitance after 6000 cycles. This study gives new insights into the role of CNT templates in the adjustment of molecular structure, porosity, and electronic property of CMPs for the high-performance electrochemical energy storage.