2.2.1. Polyisocyanates 6117 2.2.2. Polysilanes 6118 2.2.3. Polyacetylenes 6120 2.3. Foldamer-Based Helical Polymers 6124 2.3.1. Click Polymerization 6126 2.3.2. Ring-Closing Reaction 6126 2.4. Other Types of Helical Polymers 6127 2.4.1. π-Conjugated Helical Polymers 6127 2.4.2. Metallosupramolecular Helical Polymers 6128 2.5. Induced Helical Polymers 6130 2.5.1. Induced Helical Polyacetylenes 6130 2.5.2. Other Induced Helical Polymers and Oligomers 6132

Helical polymers: synthesis, structures, and functions

Covalent organic frameworks (COFs) are attractive candidates for advanced water-treatment membranes owing to their high porosity and well-organized channel structures. Herein, the continuous two-dimensional imine-linked COF-LZU1 membrane with a thickness of only 400 nm was prepared on alumina tubes by in situ solvothermal synthesis. The membrane shows excellent water permeance (ca. 760 L m-2  h-1  MPa-1 ) and favorable rejection rates exceeding 90 % for water-soluble dyes larger than 1.2 nm. The water permeance through the COF-LZU1 membrane is much higher than that of most membranes with similar rejection rates. Long-time operation demonstrates the outstanding stability of the COF-LZU1 membrane. As the membrane has no selectivity for hydrated salt ions (selectivity <12 %), it is also suitable for the purification of dye products from saline solutions. The excellent performance and the outstanding water stability render the COF-LZU1 membrane an interesting system for water purification.

High-Flux Membranes Based on the Covalent Organic Framework COF-LZU1 for Selective Dye Separation by Nanofiltration.

Covalent organic frameworks (COFs) have been proposed as alternative candidates for molecular sieving membranes due to their chemical stability. However, developing COF membranes with narrowed apertures close to the size of common gas molecules is a crucial task for selective gas separation. Herein, we demonstrate a new type of a two-dimensional layered-stacking COF–COF composite membrane in bilayer geometry synthesized on a porous support by successively regulating the growth of imine-based COF-LZU1 and azine-based ACOF-1 layers via a temperature-swing solvothermal approach. The resultant COF-LZU1–ACOF-1 bilayer membrane has much higher separation selectivity for H2/CO2, H2/N2, and H2/CH4 gas mixtures than the individual COF-LZU1 and ACOF-1 membranes due to the formation of interlaced pore networks, and the overall performance surpasses the Robeson upper bounds. The COF-LZU1–ACOF-1 bilayer membrane also shows high thermal and long-time stabilities.

Covalent Organic Framework–Covalent Organic Framework Bilayer Membranes for Highly Selective Gas Separation

Microporous polymers are covalently bound, entirely organic materials which possess very high surface areas. These materials have been intensively studied within recent years and various interesting properties and possible applications have been discovered and described. This review article starts with the question, what makes microporous polymers special and are there certain features which differentiate them from other microporous materials? Indeed, there are some special structural and functional features found in microporous polymers which make them really unique and merit further exploration. We focus here on microporous polymers which are solution-processable, can be produced as thin films on electrodes by oxidative polymerizations, are π-conjugated organic semiconductors, or which provide the possibility to introduce and exploit distinct functional groups in an otherwise non-functional highly porous environment. Emerging applications for these microporous polymers which make explicit use of these unique features are further presented.

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Trends and challenges for microporous polymers

Lewis-Acid-Catalyzed Interfacial Polymerization of Covalent Organic Framework Films

Although two-dimensional polymers (2DPs) and related materials are very attractive subjects for research because they are expected to function as ideal gas separation membrane materials, we need to...

Two-Dimensional and Related Polymers: Concepts, Synthesis, and their Potential Application as Separation Membrane Materials

One of the authors discovered helix-sense-selective polymerization (HSSP) of an achiral substituted phenylacetylene which has two hydroxymethyl groups and a relatively hydrophobic substituent by using a chiral catalytic system in 2003. The one-handed helicity is stable and static in nonpolar solvents because it is maintained by intramolecular hydrogen bonds. Since the resulting polymer has extremely tight helicity in its main chain, it shows many interesting and unusual properties including highly selective photocyclic aromatization (SCAT). In this review, the discovery and development of the HSSP and SCAT reactions, and the properties and application of the resulting polymers prepared by HSSP and the resulting supramolecular polymers prepared by SCAT will be examined.

Helix-Sense-Selective Polymerization of Achiral Phenylacetylenes and Unique Properties of the Resulting Cis-cisoidal Polymers

Two Modes of Asymmetric Polymerization of Phenylacetylene Having a l-Valinol Residue and Two Hydroxy Groups

Three novel chiral phenylacetylenes having an octyloxyethanolamine residue derived from a l-aminoalcohol and two hydroxymethyl groups were synthesized and polymerized by two achiral catalysts ((nbd)Rh+[η6-(C6H5)B−(C6H5)3] and [Rh(nbd)Cl]2/triethylamine (TEA)) and a chiral catalytic system ([Rh(nbd)Cl]2/(S)- or (R)-phenylethylamine ((S)- or (R)-PEA)). All of the resulting polymers showed Cotton effects at wavelengths around 430 nm. This observation indicated that they had an excess of one-handed helical backbones. Positive and negative Cotton effects were observed for the polymers having an l-valinol residue produced by using (S)- and (R)-PEA as a cocatalyst, respectively, although the monomers had the same chirality. The two polymers having an l-alaninol or l-phenylalaninol residues obtained by using (S)- and (R)-PEA as a cocatalyst showed CD absorptions with identical signs. Therefore, we found that the chiral monomer having an l-valinol residue was suitable for both modes of asymmetric polymerization, t...

Three Mechanisms of Asymmetric Polymerization of Phenylacetylenes Having an l-Amino Ether Residue and Two Hydroxy Groups

Superhydrophobic conjugated microporous polymer-coated sponges: Synthesis and application for highly efficient oil/water separation and the recovery of palladium ions

Hongge Jia

Papers

Two-Dimensional and Related Polymers: Concepts, Synthesis, and their Potential Application as Separation Membrane Materials

Helix-Sense-Selective Polymerization of Achiral Phenylacetylenes and Unique Properties of the Resulting Cis-cisoidal Polymers

Two Modes of Asymmetric Polymerization of Phenylacetylene Having a l-Valinol Residue and Two Hydroxy Groups

Three Mechanisms of Asymmetric Polymerization of Phenylacetylenes Having an l-Amino Ether Residue and Two Hydroxy Groups

Superhydrophobic conjugated microporous polymer-coated sponges: Synthesis and application for highly efficient oil/water separation and the recovery of palladium ions