Hollow Mesoporous Organic Polymeric Nanobowls and Nanospheres: Shell Thickness and Mesopore-Dependent Catalytic Performance in Sulfonation, Immobilization of Organocatalyst, and Enantioselective Organocascade

Abstract

Heterogeneous asymmetric multicomponent/multicatalytic organocascade faces the enormous challenges of tedious immobilization of catalysts, mass transfer, and stereoselective control. In this paper, the mesopore-abundant and well-shaped hollow mesoporous organic polymers, nanobowls (HMOPBs) and nanospheres (HMOPSs), are fabricated via emulsion polymerization of styrene on a polystyrene (PS) core and then removal of PS, accompanied by the adsorption of Co2+ ions, transformation of Co2+ into Co­(OH)2, and final removal of Co­(OH)2. Among them, the nanobowl HMOPBs­(a) with hollow interiors, mesoporous shells, and thin shell thickness (16 nm) possesses the largest surface area (185.7 m2 g–1) and displays the highest reaction kinetics in the sulfonation (2.85 mmol H+ g–1) and then immobilization of 9-amino­(9-deoxy)epi-quinine (QNNH2, 1.35 mmol g–1). For the 2,4-substituted bulky reactants in an asymmetric double-Michael cascade, the as-fabricated functional nanobowl can provide a suitable microenvironment to meet the requirements of the good to excellent double-Michael organocascades, which originates from its thin shell thickness and mesopore-dependent shell.

Water-Soluble Fluorescent Nanobowls Constructed by Multiple Supramolecular Assembly

“…Nanobowls are a class of novel asymmetric structures. , The bowl-shaped architecture with hollow interiors and openings on their surface possess a large surface area, which render their favorable applications in catalysis, supercapacitors, and drug delivery . A number of synthetic strategies toward bowl-shaped structures have been developed, such as the self-assembly from amphiphilic block copolymers, − aggregation from molecular motor induced by solvent mixing, and synergy supramolecular forces between the side chains of polymers .…”

Cross-Linked Porous Polymers as Heterogeneous Organocatalysts for Task-Specific Applications in Biomass Transformations, CO2 Fixation, and Asymmetric Reactions

“…Hence, this study clearly signifies enantio-discrimination, governed by the conformational rigidity of the active centers and the confinement effect of mesopores. The same group later prepared hollow mesoporous polymeric nanobowls and nanospheres via emulsion polymerization of styrene, which was sulfonated and utilized as a host for immobilizing 9-amino­(9-deoxy) epi -quinine (QNNH 2 ) . This functional nanomaterial through its unique microenvironment and narrow shell thickness (16 nm) shows excellent double Michael organocascade reaction due to moderate porosity (BET surface area: 116–185 m 2 g –1 ), and the presence of large mesopores (15–16.3 nm).…”

“…The same group later prepared hollow mesoporous polymeric nanobowls and nanospheres via emulsion polymerization of styrene, which was sulfonated and utilized as a host for immobilizing 9-amino(9-deoxy)epi-quinine (QNNH 2 ). 82 This functional nanomaterial through its unique microenvironment and narrow shell thickness (16 nm) shows excellent double Michael organocascade reaction due to moderate porosity (BET Wang and others 83 proposed a unique bottom-up approach for the preparation of chiral porous polymers containing both micropores (49.7%), as well as mesopores (50.3%). The synthesis of POPs containing embedded asymmetric sites is unique although challenging and remains unexplored.…”

Multifunctional Integrated Compartment Systems for Incompatible Cascade Reactions Based on Onion-Like Photonic Spheres

“…Approaches to achieving compatible goals were pioneered by Patchornik and co-workers, who developed a “wolf and lamb” reaction strategy in which two insoluble polymer-immobilized catalysts bypassed cross-inhibition. Avnir further exploited this approach by encapsulating opposing catalysts in a sol–gel. − Recently, increasing non-natural multicompartment systems (MCSs) have been demonstrated by immobilization or encapsulation of incompatible substances on polymers, ,,,,− mesoporous materials, − hydrogels, graphene, MOFs, , cages, − Pickering emulsions, − and protocells . These efforts are encouraging examples of multicompartmentalized microreactor architectures to enable incompatible cascade reactions.…”