Light responsive membranes for gas separation

Recent developments in the field of coordinated porous materials (including metal organic frameworks and zeolitic imidazolate frameworks) have demonstrated that it is possible to tailor CO2 sorbents that respond dynamically to illumination with UV and/or broadband light, such that they cyclically adsorb and desorb CO2 according to the illumination state. This has been achieved via several routes, including through the use of light-responsive ligands, light-responsive guest molecules located within the pores, and via adsorption of a light-responsive dye. Since the use of these materials as light-responsive sorbents is challenging (due to engineering constraints in providing unhindered gas and light access to as much of the sorbent as possible), it is highly desirable to incorporate them into thin polymeric membranes to create mixed-matrix membranes with light responsive properties. This could lead to membranes with switchable separation characteristics, or other desirable properties such as some form of self-cleaning or self-regeneration after pore blocking. This presentation will unveil the recent developments in our lab as we develop these novel mixed-matrix membrane materials, including an overview of the light-responsive porous materials we have synthesised and characterised, the design and performance of our newest illuminated test cells for both flat sheet and hollow-fibre membranes (using a unique in-situ LED lighting arrangement to provide maximum illumination and simplify gas sealing)

Photoresponsive Polymer and Polymer Composite Membranes for Gas Separation

Stimuli-responsive materials, referred to as “smart” or “intelligent” materials, have gained significant attention in the separation fields, including gas separation. Among a variety of available stimuli, the use of light as a nondestructive, cost-efficient, chemical-reagent-free stimulus with a relatively fast response is very promising. Herein, we summarize and highlight the approaches applied for the synthesis of photoresponsive organic polymeric membranes, inorganic metal–organic framework thin films, and inorganic–organic mixed-matrix membranes. We discuss the application of these materials for gas separation and provide selected state-of-the-art examples from recently conducted studies. Additionally, the photoresponsive gas separation membrane testing cell plays a crucial role in evaluating and comparing the performance of photoresponsive membranes in the gas separation process. Therefore, we review the development of photoresponsive gas separation membrane testing cells along with the ascribed drawbacks and limitations. A third generation testing system designed to highlight test accuracy is proposed and discussed

Solvent‐induced enantioselectivity reversal in a chiral metal organic framework

Solvent-induced enantioselectivity reversal is a rarely reported phenomenon in porous homochiral materials. Similar behavior has been studied in chiral high performance liquid chromatography, where minor modifications to the mobile phase can induce elution order reversal of two enantiomers on a chiral stationary phase column. We report the first instance of solvent-induced enantioselectivity reversal in a homochiral metal organic framework. Further, we highlight the complex enantioselectivity behavior of homochiral metal organic frameworks toward racemic mixtures in the presence of solvents through racemate-solvent enantioselectivity and loading experiments as well as enantiopure-solvent loading experiments. We hypothesize that this interesting selectivity reversal behavior is likely to be observed in other competitive adsorption, nonchiral selective processes involving a solvent

Green synthesis of polymeric membranes: Recent advances and future prospects

peer reviewedPolymeric membranes are widely used in gas separations, liquid separations, and other processes such as fuel cells. However, methods and processes for manufacturing these membranes are usually harmful to the environment and/or human health. Although many new materials and synthesis methods are reported every year, green synthesis only makes up a small proportion. Therefore, more efforts are necessary to raise researchers’ awareness to green synthesis of membranes. One popular strategy to greenly synthesize membranes is to avoid toxic organic solvents or use water to replace organic solvents completely. However, many reported green methods could only realize green synthesis partly. The ultimate goal is to synthesize membranes in a completely eco-friendly way, where raw materials, membrane preparation, post-treatment, and other involved procedures are all ‘green’

Getting Chemical and Biochemical Engineers Excited about Additive Manufacturing

A new course was designed to attract chemical and bioengineers to additive manufacturing and to provide them with an effective approach to this new field. The goal is a wider use of the advantages of additive manufacturing for complex multifunctional components in chemical process engineering. We describe the structure of the course and the experiences from the first two years. Students show great interest and are able to develop their own functional components with assistance. Yet many have deficits in the use of CAD software, which will be remedied in the future through a specific lecture

Natural and recycled materials for sustainable membrane modification: Recent trends and prospects

Despite water being critical for human survival, its uneven distribution, and exposure to countless sources of pollution make water shortages increasingly urgent. Membrane technology offers an efficient solution for alleviating the water shortage impact. The selectivity and permeability of membranes can be improved by incorporating additives of different nature and size scales. However, with the vast debate about the environmental and economic feasibility of the common nanoscale materials in water treatment applications, we can infer that there is a long way before the first industrial nanocomposite membrane is commercialized. This stumbling block has motivated the scientific community to search for alternative modification routes and/or materials with sustainable features. Herein, we present a pragmatic review merging the concept of sustainability, nanotechnology, and membrane technology through the application of natural additives (e.g., Clays, Arabic Gum, zeolite, lignin, Aquaporin), recycled additives (e.g., Biochar, fly ash), and recycled waste (e.g., Polyethylene Terephthalate, recycled polystyrene) for polymeric membrane synthesis and modification. Imparted features on polymeric membranes, induced by the presence of sustainable natural and waste-based materials, are scrutinized. In addition, the strategies harnessed to eliminate the hurdles associated with the application of these nano and micro size additives for composite membranes modification are elaborated. The expanding research efforts devoted recently to membrane sustainability and the prospects for these materials are discussed. The findings of the investigations reported in this work indicate that the application of natural and waste-based additives for composite membrane fabrication/modification is a nascent research area that deserves the attention of both research and industry

Polymer-assisted modification of metal-organic framework MIL-96 (Al): influence of HPAM concentration on particle size, crystal morphology and removal of harmful environmental pollutant PFOA.

peer reviewedA new synthesis method was developed to prepare an aluminum-based metal organic framework (MIL-96) with a larger particle size and different crystal habits. A low cost and water-soluble polymer, hydrolyzed polyacrylamide (HPAM), was added in varying quantities into the synthesis reaction to achieve >200% particle size enlargement with controlled crystal morphology. The modified adsorbent, MIL-96-RHPAM2, was systematically characterized by SEM, XRD, FTIR, BET and TGA-MS. Using activated carbon (AC) as a reference adsorbent, the effectiveness of MIL-96-RHPAM2 for perfluorooctanoic acid (PFOA) removal from water was examined. The study confirms stable morphology of hydrated MIL-96-RHPAM2 particles as well as a superior PFOA adsorption capacity (340 mg/g) despite its lower surface area, relative to standard MIL-96. MIL-96-RHPAM2 suffers from slow adsorption kinetics as the modification significantly blocks pore access. The strong adsorption of PFOA by MIL-96-RHPAM2 was associated with the formation of electrostatic bonds between the anionic carboxylate of PFOA and the amine functionality present in the HPAM backbone. Thus, the strongly held PFOA molecules in the pores of MIL-96-RHPAM2 were not easily desorbed even after eluted with a high ionic strength solvent (500 mM NaCl). Nevertheless, this simple HPAM addition strategy can still chart promising pathways to impart judicious control over adsorbent particle size and crystal shapes while the introduction of amine functionality onto the surface chemistry is simultaneously useful for enhanced PFOA removal from contaminated aqueous systems