Minghong Zhou

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.

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.

“Click Chemistry” Mediated Functional Microporous Organic Nanotube Networks for Heterogeneous Catalysis

The synthesis of azide functional microporous organic nanotube networks (N3-MONNs) via a Friedel-Crafts hyper-cross-linking reaction is reported. Subsequently, a general method for obtaining heterogeneous catalysts through a Cu-catalyzed alkyne-azide reaction is presented. The small-molecule catalysts such as 2,2,6,6,-tetramethylpiperidine-1-oyl and 4-(N,N-dimethylamino)pyridine can be anchored into the MONNs. Owing to the hierarchically porous structure and high surface area, these catalysts show high activity in selective oxidation of alcohols and acylation reaction, respectively.

Preparation of multifunctional hollow microporous organic nanospheres via a one-pot hyper-cross-linking mediated self-assembly strategy

Herein we report a universal method for the preparation of multifunctional hollow microporous organic nanospheres (H-MONs) using functional aromatic monomers (such as benzylamine, 2,2-bipyridine, triphenylamine or carbazole) and the polylactide-b-polystyrene (PLA-b-PS) diblock copolymer as precursors based on a one-pot hyper-cross-linking mediated self-assembly strategy. In this method, co-hyper-cross-linking among the PS block and various aromatic monomers forms the functional microporous organic shell frameworks, while the degradable PLA block produces the hollow core structure. By introducing functional organic ligands, various metal-loaded or heteroatom-doped H-MONs can be successfully synthesized. Owing to their high special surface area, robust organic framework, and hierarchically porous structure, these multifunctional H-MONs exhibited excellent catalytic activity or high adsorption capacity for radioactive iodine. The proposed one-pot strategy may provide a general approach to produce a variety of functional H-MONs for various applications in the future.

A Polymerization-Cutting Strategy: Self-Protection Synthesis of Thiol-Based Nanoporous Adsorbents for Efficient Mercury Removal

Highly toxic heavy metal ions such as mercury ions (Hg2+ ) are a great threat to human life and the environment. Developing new strategies and materials to remove the toxic heavy metal ions has attracted more and more attentions. Herein a facile self-protection synthesis of thiol-based nanoporous adsorbents for efficient mercury removal via a polymerization-cutting strategy is reported. The direct free-radical polymerization of divinyl disulfide derivative and subsequently cutting off the disulfide linkage, without post-synthesis or modification, can give rise to an exceptionally high density of thiol chelating sites. Moreover, the resultant thiol-based nanoporous adsorbents (NAs-SH) exhibit a high saturation uptake capacity (1240 mg g-1 ) and reused ability for mercury removal from water solution. The proposed polymerization-cutting strategy may provide an alternative and cost-effective method for the design and synthesis of various efficient nanoporous adsorbents at large scale in the future.