Zidong He

Carboxyl-containing microporous organic nanotube networks as a platform for Pd catalysts

In this work, we present a novel synthesis of carboxyl-containing microporous organic nanotube networks (COOH-MONNs) by combination of hyper-cross-linking and molecular templating of core–shell bottlebrush copolymers. Highly dispersed palladium nanoparticles (Pd NPs) anchored on the COOH-MONNs (Pd@MONNs) have been prepared by in situ thermal decomposition of Pd(OAc)2. The Pd@MONNs composites were characterized by XRD, N2 adsorption, TEM, ICP-AES and XPS. The results show that bulk production of highly dispersed palladium nanoparticles can be achieved by a thermal decomposition method. Moreover, the obtained Pd@MONNs exhibit high activities for the Suzuki–Miyaura cross-coupling reaction and can be easily recovered and reused. This approach of using MONNs as a platform for catalysts is expected to open doors for new types of catalytic support for practical applications.

Synthesis of triphenylphosphine-based microporous organic nanotube framework supported Pd catalysts with excellent catalytic activity

This work reports an efficient strategy to prepare a type of triphenylphosphine-based microporous organic nanotube framework (MONFs-PPh3) as a platform for Pd catalyst (MONFs-PPh3@Pd) via hyper-crosslinking core–shell multicomponent bottlebrush copolymers. The triphenylphosphine ligands not only act as functional groups, but as a supporting part of the nanotube walls. This novel material possesses great adjustability for the mesopore sizes of nanotubes and the concentration of triphenylphosphine ligands within the frameworks, which can be tuned during bottlebrush copolymer synthesis at the molecular level. Moreover, MONFs-PPh3@Pd exhibits excellent catalytic activity in the Suzuki–Miyaura reaction of aryl chlorides in aqueous media, which is much higher than that of the corresponding disordered microporous organic polymer-based Pd catalyst and homogeneous molecular catalysts under similar conditions.

Functionalized microporous organic nanotube networks as a new platform for highly efficient heterogeneous catalysis

In this paper, we report a novel synthesis of amino-functionalized microporous organic nanotube networks (NH2-MONNs) by combination of hyper cross-linking and molecular templating of multicomponent bottlebrush copolymers. The amino-modified MONNs constructed from a unique trimodal micro, meso and macroporous architecture and flexible frameworks possess a specific surface area of 936 m2 g−1 and a pore volume of 1.67 cm3 g−1. Owing to the large surface area, good multi-porosity interconnectivity and excellent swelling properties in organic solvents, the resultant NH2-MONNs show highly efficient heterogeneous catalysis and excellent reusability in the Knoevenagel condensation and Henry reaction.

Microporous organic nanotube network supported acid and base catalyst system for one-pot cascade reactions

In this work, we reported a novel synthesis of acid or base functionalized microporous organic nanotube networks (MONNs) by hyper-crosslinking core–shell bottlebrush copolymers. With a high specific surface area, excellent hierarchical porosity and site-isolation features, the resultant SO3H– and NH2–MONNs catalyst systems present an excellent catalytic performance for deacetalization-Knoevenagel cascade reactions.

Three-Arm Branched Microporous Organic Nanotube Networks

Here, a novel method is demonstrated for the preparation of three-arm branched microporous organic nanotube networks (TAB-MONNs) based on molecular templating of three-arm branched core-shell bottlebrush copolymers and Friedel-Crafts alkylation reaction. The unique three-arm branched bottlebrush copolymers are synthesized by a combination of atom transfer radical polymerization, reversible addition-fragmentation chain transfer polymerization, and ring-opening polymerization techniques. In this approach, the length and diameter of branched tube units can be well-controlled by rational molecular design. Moreover, the as-prepared TAB-MONNs possess a high surface area and exhibit a superior adsorption capacity for Rhodamine 6G (R6G) and p-cresol.

In Situ Formation of Dual-Phase Thermosensitive Ultrasmall Gold Nanoparticles.

A novel method for the in situ synthesis of dual-phase thermosensitive ultrasmall gold nanoparticles (USGNPs) with diameters in the range of 1-3 nm was developed by using poly(N-isopropylacrylamide)-block-poly(N-phenylethylenediamine methacrylamide) (PNIPAM-b-PNPEDMA) amphiphilic diblock copolymers as ligands. The PNPEDMA block promotes the in situ reduction of gold precursors to zero-valent gold and subsequently binds to the surface of gold nanoparticles, while PNIPAM acts as a stabilizing and thermosensitive block. The as-synthesized USGNPs stabilized by a thermosensitive PNIPAM layer exhibit a sharp, reversible, clear-opaque transition in aqueous solution between 30 and 38 °C. An unprecedented finding is that these USGNPs also show a reversible soluble-precipitate transition in nonpolar organic solvents such as chloroform at around 0 °C under acidic conditions.

Acid–base bifunctional amphiphilic organic nanotubes as a catalyst for one-pot cascade reactions in water

A novel acid–base bifunctional amphiphilic organic nanotube (acid–base-nanotube) containing 1-(2-(prop-2-yn-1-yloxy)ethyl)-1H-imidazole (PEI) groups as basic sites on the wall and benzenesulfonic acid (BSA) groups as acidic sites on the corona of nanotubes was successfully synthesized by a combination of molecular-template core–shell bottlebrush copolymers and click reaction. Owing to the hydrophobic cavity microenvironments, a hydrophilic corona, and site-isolation features of organic tubular structures, the resultant acid–base-nanotube showed high catalytic performance for one-pot deacetalization-Knoevenagel cascade reactions in water.

Fe-Porphyrin functionalized microporous organic nanotube networks and their application for the catalytic olefination of aldehydes and carbene insertion into N–H bonds

Novel meso-tetraphenylporphyrin iron(III) chloride (Fe(TPP)Cl) functionalized microporous organic nanotube networks (Fe(TPP)Cl-MONNs) were successfully synthesized by an in situ hyper-crosslinking reaction between core–shell bottlebrush copolymers and Fe(TPP)Cl. The obtained Fe(TPP)Cl-MONN catalyst possesses a hierarchical porous structure, large surface area and good stability, which exhibits high catalytic activity and excellent reusability in the olefination of aldehydes and carbene insertion into N–H bonds with ethyl diazoacetate.

Synthesis of magnetic microporous organic nanotube networks for adsorption application

In this work, we report a novel synthesis of magnetic microporous organic nanotube networks (Fe3O4-MONNs) by an in situ hyper-cross-linking reaction between magnetic nanoparticles and core–shell bottlebrush copolymers. The resulting Fe3O4-MONNs magnetic hybrid materials display a hierarchically porous structure with nanotube morphology, large surface area (648 m2 g−1) and uniform mesochannels (∼4 nm). Due to abundant anionic carboxylate groups produced as end-groups after polylactide (PLA) core degradation in the bottlebrush copolymers, the Fe3O4-MONNs showed a selective adsorption behavior for the cationic dyes. Moreover, the Fe3O4-MONNs possess superparamagnetism and high saturation magnetization (19.8 emu g−1), which allows them to be easily separated by an external magnetic field and subsequently reused. Therefore, this work provides a promising method for the design and synthesis of magnetic microporous organic nanotube networks, which can be used for the practical separation of organic dyes, as well as having other potential applications in the fields of absorption, fast separation and heterogeneous catalysis.

Microporous Organic Nanotube Networks from Hyper Cross-linking Core-shell Bottlebrush Copolymers for Selective Adsorption Study

We report a synthesis of microporous organic nanotube networks (MONNs) by a combination of hyper cross-linking and molecular templating of core-shell bottlebrush copolymers. The intrabrush and interbrush cross-linking of polystyrene (PS) shell layer in the core-shell bottlebrush copolymers led to the formation of micropores and large-sized nanopores (meso/macrospores) in MONNs, respectively, while selective removal of polylactide (PLA) core layer generated mesoporous tubular structure. The size of PLA-templated mesoporous cores and porous structure both at micro- and meso-scale could be controlled by simple tuning of the ratio of core/shell or the PLA core fraction in the bottlebrush precursors. Moreover, the resultant MONNs showed a highly selective adsorption capacity for the positively charged dyes on the basis of multi-porosity and carboxylate group-rich structure. In addition, MONNs also exhibited effective performance in size-selective adsorption of biomacromolecules. This work represents a new avenue for the preparation of MONNs and also provides a new application for molecular bottlebrushes in nanotechnology.