Preparation of a Dual-Functionalized Acid-Base Macroporous Polymer via High Internal Phase Emulsion Templating as a Reusable Catalyst for One-Pot Deacetalization-Henry Reaction

A macroporous dual-functional acid-base covalent organic polymer catalyst poly(St-VBC)-NH₂-SO₃H was prepared using high internal phase emulsion polymerization using vinylbenzyl chloride (VBC), styrene (St), and divinylbenzene (DVB) as substrates toluene as a porogenic solvent, and subsequent modification with ethylenediamine and 1,3-propane sultone. The role of various amounts of toluene as the porogenic solvent as well as the amount of 1,3-propane sultone (different ratio of acid/base sites) on the structure of the prepared materials have been carefully investigated. The prepared materials were characterized by Fourier transform infrared (FT-IR), CHNS elemental analysis, energy-dispersive X-ray (EDX), elemental mapping, field emission scanning electron microscopy (FE-SEM), and thermalgravimetric analysis (TGA). The catalytic activity of the poly(St-VBC)-NH₂-SO₃H series with different acid/base densities was assessed for one-pot cascade C-C bond-forming reactions involving deacetylation-Henry reactions. The poly(St-VBC)-NH₂-SO₃H(20) sample bearing 1.82 mmol/g of N (base site) and 1.16 mmol/g (acid site) showed the best catalytic activity. The catalyst demonstrated superior activity compared to the homogeneous catalysts, poly(St-DVB)-SO₃H+EDA, poly(St-VBC)-NH₂+chlorosulfonic acid, and poly(St-DVB)-SO₃H+poly(St-VBC)-NH₂ as the catalyst system. The optimized catalyst showed excellent catalytic performance with 100% substrate conversion and 100% yield of the final product in the one-pot production of β-nitrostyrene from benzaldehyde dimethyl acetal under cascade reactions comprising acid-catalyzed deacetalization and base-catalyzed Henry reactions. It was shown that these catalysts were reusable for up to four consecutive runs with a very slight loss of activity. The excellent performance of the catalyst was attributed to the excellent chemical and physical properties of the developed support since it provides an elegant route for preparing site-isolated acid-base dual heterogenized functional groups and preventing their deactivation via chemical neutralization.

Tuning acid–base cooperativity to create bifunctional fiber catalysts for one-pot tandem reactions in water

A simple and straightforward route to create acid–base bifunctional fiber catalysts for efficient one-pot tandem deprotection-Knoevenagel reactions in water.

Controllable Preparation of Monodisperse Mesoporous Silica from Microspheres to Microcapsules and Catalytic Loading of Au Nanoparticles

A unique structural transition from pomegranate-like monodisperse mesoporous silica microspheres (M-MSMs) with tunable mesopores to mesoporous silica microcapsules has been reported. The unique evolution occurred together with varying the cross-linking degrees (CLDs) of templates. Herein, using monodisperse sulfonated cross-linked polystyrene (S-CLPS) as templates, S-CLPS/SiO₂ composite microspheres were synthesized by the sol-gel method. Subsequently, the templates were removed by calcination to obtain the M-MSMs or microcapsules. The pore sizes of M-MSMs could be tailored from 3.2 to 7.4 nm by facilely varying the CLDs from 0.5 to 20%. Interestingly, mesoporous silica microcapsules were gradually formed when the CLDs were beyond 20%. Meanwhile, the specific surface area also could be adjusted by this strategy without hardly affecting the monodispersity, and the specific surface area increased to 391.9 m²/g. Significantly, Au@M-MSM was prepared by supporting Au nanoparticles (NPs) on M-MSM and used as nanocatalysts to reduce 4-nitrophenol (4-NP). The ultrathin shell and interconnected three-dimensional (3D) porous structure of M-MSMs can increase the mass transfer and protect the Au NPs from leakage, which reveals high recyclability and high conversion (>95%) after 10 regeneration-catalysis cycles. This approach provides a nanotechnology platform for the preparation of mesoporous silica materials with different microstructures, which will have enormous potential in practical applications involving different molecular sizes.

Physically mixed catalytic system of amino and sulfo-functional porous organic polymers as efficiently synergistic co-catalysts for one-pot cascade reactions

Acid/base bi-functional polymeric materials were prepared using physically mixed porous polymers P(DVB-VBS) with sulfonic acid and P(DVB-VBA) with amino groups for various cascade reactions.

Synthesis of 3D-Ordered Macro/Microporous Yolk-Shelled Nanoreactor with Spatially Separated Functionalities for Cascade Reaction

Constructing three-dimensional (3D) hierarchical materials with spatial compartmentalization of multiple catalytic functionalities effectively facilitates the chemical processes' intensification, especially for bulky-molecule-involved cascade reaction. Herein, a facile and novel core-shell colloidal crystal templating strategy was developed to synthesize highly ordered arrays of integrated yolk-shelled nanoreactor consisting of monolithically interconnected ZIF-8 shell and sulfonated polystyrene yolks decorated with rhodium nanoparticles. The obtained nanoreactor achieves efficient catalytic one-pot cascade Knoevenagel condensation-hydrogenation reactions for larger molecules, by taking advantage of the superior mass diffusion properties of the hierarchical macro/microporous metal-organic framework (MOF) skeleton, robust monolith nature, and spatially separated functionalities. This work offers an important strategy for preparing MOF-based composites with a hierarchical framework, accelerating various applications of MOFs, such as electrochemical applications, photothermal conversion, and heterogeneous catalysis.

Encapsulating mesoporous metal nanoparticles: towards a highly active and stable nanoreactor for oxidative coupling reactions in water

We design and prepare a highly active and stable nanoreactor by encapsulating mesoporous metal nanoparticles for efficient production of α,β-unsaturated ketones via a one-pot oxidative coupling reaction.