Pd Nanoparticle-Loaded Smart Microgel-Based Membranes as Reusable Catalysts

Abstract

In this work, palladium-loaded smart membranes made by UV cross-linking of thermoresponsive microgels are prepared to obtain a reusable, catalytically active material which can, for example, be implemented in chemical reactors. The membranes are examined with respect to their coverage of a supporting mesh via atomic force microscopy measurements. Force indentation mapping was performed in the dried, collapsed state and in the swollen state in water to determine the Young modulus. Furthermore, we compare the catalytic activity of the membrane with the corresponding suspended colloidal nanoparticle microgel hybrids. For this purpose, the reduction of 4-nitrophenol is an established model reaction to quantify the catalytic activity by UV–vis spectroscopy. The membrane is embedded inside a continuous stirred tank reactor equipped for continuous monitoring of the reaction progress. Although catalysis with membranes shows lower catalytic activity than freely dispersed particles, membranes allow straightforward separation and recycling of the catalyst. The fabricated membranes in this work show no decrease in catalytic activity between several cycles, unlike free particles. The feasible and durable deposition of catalytically active inter-cross-linked microgel particles on commercial nylon meshes as supporting scaffolds, as demonstrated in this work, is promising for up-scaling of continuous industrial processes.

A review of stimuli-responsive polymer-based gating membranes

“…This may include better permeation when pores are open, allowing for higher fluxes, while efficiently blocking flux when closed. One can also imagine adding functions to the gating membranes, like embedded catalytic particles (see Sabadasch et al 55 ) which could favor a desired reaction, like decomposition of some pollutant during filtering. Given the many possible applications, in particular those related to environmental issues (decontamination, waste-water treatment, controlled catalytic reactions…), we are looking forward to following new adventures in this field.…”

“…The contribution by Sabadasch et al 55 shows that the UV cross-linked smart membranes can be loaded with nanoparticles (here palladium) that can be used in catalytic applications. The free-standing photo-crosslinked membranes were deposited on a nylon mesh to achieve higher mechanical stability (see Fig.…”

Laser Patterning of Porous Support Membranes to Enhance the Effective Surface Area of Thin-Film Composite-Facilitated Transport Membranes for CO2 Separation

“…To efficiently separate CO 2 , the amine layer should have a high CO 2 absorption capacity and rapid absorption dynamics, similar to amine-based CO 2 absorbents used in the chemical absorption process. ,, However, most high-performance CO 2 absorbents cannot form defect-free thin layers on the top of porous support membranes . Our strategy overcomes this issue by incorporating hydrogel microparticles (GPs) into the amine layers (Scheme b). , Well-swollen GPs, whose diameter is larger than that of the pores on support membranes, autonomously assemble into a defect-free hydrogel nanolayer. ,,, Low-pressure air-spray coating was applied to fabricate the defect-free thin separation layer (with a large surface area) on the surfaces of micropatterned porous support membranes. − The enlarged effective surface area of the patterned membrane will accelerate CO 2 permeation through the separation layer by promoting the surface dissolution and desorption of CO 2 .…”

Compression and Ordering of Hollow Microgels in Monolayers Formed at Liquid–Liquid Interfaces

“…3−6 In contrast, microgels are capable of bearing strong deformations and flattening during adsorption at the interface, which leads to several major differences in their behavior: (a) due to the surface activity, a part of microgels that is in contact with the interface stretches out, occupying a larger area to minimize the energy of unfavorable contacts between immiscible liquids until this energy gain is balanced by the internal elasticity, 7,8 (b) the particles protrude into the fluids according to their respective affinities, 9,10 and (c) the ordering in the monolayer can be tuned both by their swelling degree and mechanical compression. 5,6,11 These features can be used to fabricate functional membranes and coatings for application in catalysis, 12 medicine, 13 or nanolithography. 14−16 The behavior of microgels at the interfaces strongly depends on their architecture.…”

“…Polymer microgels are soft and deformable colloidal particles that possess the ability to change their shape and porosity in various solvents and interfaces. , The small size (from tens of nanometers to several microns) and their unique physical properties allow considering such macromolecular objects in-between soft polymer macromolecules, solid particles, and surfactants. Similar to hard colloids, microgels can be used as stabilizers for Pickering emulsions or to create a densely packed monolayer with long-range order at the fluid interface. − In contrast, microgels are capable of bearing strong deformations and flattening during adsorption at the interface, which leads to several major differences in their behavior: (a) due to the surface activity, a part of microgels that is in contact with the interface stretches out, occupying a larger area to minimize the energy of unfavorable contacts between immiscible liquids until this energy gain is balanced by the internal elasticity, , (b) the particles protrude into the fluids according to their respective affinities, , and (c) the ordering in the monolayer can be tuned both by their swelling degree and mechanical compression. ,, These features can be used to fabricate functional membranes and coatings for application in catalysis, medicine, or nanolithography. − …”