Flexible single-layer ionic organic–inorganic frameworks towards precise nano-size separation

Abstract

Consecutive two-dimensional frameworks comprised of molecular or cluster building blocks in large area represent ideal candidates for membranes sieving molecules and nano-objects, but challenges still remain in methodology and practical preparation. Here we exploit a new strategy to build soft single-layer ionic organic–inorganic frameworks via electrostatic interaction without preferential binding direction in water. Upon consideration of steric effect and additional interaction, polyanionic clusters as connection nodes and cationic pseudorotaxanes acting as bridging monomers connect with each other to form a single-layer ionic self-assembled framework with 1.4 nm layer thickness. Such soft supramolecular polymer frameworks possess uniform and adjustable ortho-tetragonal nanoporous structure in pore size of 3.4–4.1 nm and exhibit greatly convenient solution processability. The stable membranes maintaining uniform porous structure demonstrate precisely size-selective separation of semiconductor quantum dots within 0.1 nm of accuracy and may hold promise for practical applications in selective transport, molecular separation and dialysis systems.

Cyclodextrin Films with Fast Solvent Transport and Shape‐Selective Permeability

“…The flexibility of the membranes was rescued by copolymerizing cyclodextrins with flexible polymers, but this substantially decreased the concentration of cyclodextrin in the active layer, diluting their effect. Yue et al developed an ingenious approach with α‐CD as a directing agent in the formation of single‐layer ionic organic–inorganic 2D frameworks . The cavity of the α‐CDs was used as a cap for the “stick” cationic molecules used to build the frameworks.…”

Wet and Functional Adhesives from One‐Step Aqueous Self‐Assembly of Natural Amino Acids and Polyoxometalates

“…[12] As hotgun approach, involving the covalent or non-covalent grafting of the side chains of amino acids to the surface of nanoparticles,h as been utilized to trigger the aggregation of nanoparticles through the intermolecular H-bonds and the salt bridge interactions among the zwitterionic main chains of amino acids. [15] Herein, we demonstrate how the use of PMs to drive the non-covalent crosslinking of natural amino acids in aqueous solution, resulting in the formation of wet adhesives with electrochromic feature. Polyoxometalates (PMs) are particularly unique nanoclusters because of their monodispersed size,w ell-defined topology, water solubility,polyanionic surface,controllable charges,and redox properties.…”

“…[14] They have been explored serving as sticky knot to electrostatically connect the bolaform amphiphiles or polymers into soft network structures. [15] Herein, we demonstrate how the use of PMs to drive the non-covalent crosslinking of natural amino acids in aqueous solution, resulting in the formation of wet adhesives with electrochromic feature.…”

Host–Guest‐Induced Environment Tuning of 3d Ions in a Polyoxopalladate Matrix

“…While hybrid compounds of classical (Mo, W) POMs have been investigated for various applications (e.g. size‐selective separation of semiconductor quantum dots, for desulfurization of natural gas and for catalysis,), CD‐polyoxopalladate hybrids remain elusive until now.…”