Shaheen A. Al-Muhtaseb

Zeolitic imidazolate framework (ZIF-8) based polymer nanocomposite membranes for gas separation

As synthesised ZIF-8 nanoparticles (size ∼ 60 nm and specific surface area ∼ 1300–1600 m2 g−1) were directly incorporated into a model polymer matrix (Matrimid® 5218) by solution mixing. This produces flexible transparent membranes with excellent dispersion of nanoparticles (up to loadings of 30 wt%) with good adhesion within the polymer matrix, as confirmed by scanning electron microscopy, dynamic mechanical thermal analysis and gas sorption studies. Pure gas (H2, CO2, O2, N2 and CH4) permeation tests showed enhanced permeability of the mixed matrix membrane with negligible losses in selectivity. Positron annihilation lifetime spectroscopy (PALS) indicated that an increase in the free volume of the polymer with ZIF-8 loading together with the free diffusion of gas through the cages of ZIF-8 contributed to an increase in gas permeability of the composite membrane. The gas transport properties of the composite membranes were well predicted by a Maxwell model whilst the processing strategy reported can be extended to fabricate other polymer nanocomposite membranes intended for a wide range of emerging energy applications.

Advances in Tailoring Resorcinol‐Formaldehyde Organic and Carbon Gels

An overview on the preparation and properties of resorcinol-formaldehyde (RF) organic and carbon gels reveals the fascinating and remarkably flexible properties of RF carbon and organic gels and how these properties are related to the synthesis and processing conditions. The structural properties can be easily tailored by rigidly controlling such conditions. However, slight variations in some conditions may cause drastic variations in the structural characteristics, and hence properties. Therefore, the effects of different conditions must be well-understood before attempting to tailor organic or carbon gels to specific applications. The most important factors that affect the properties of an organic gel are the precursor concentrations, the catalyst type and concentration, the time and temperature of curing, and the drying method. In addition to these factors, characteristics of activated carbon gels also depend on the pyrolysis temperature and the activation method. These conditions impact the structural and performance characteristics significantly.

Controlled thermal oxidative crosslinking of polymers of intrinsic microporosity towards tunable molecular sieve membranes

Organic open frameworks with well-defined micropore (pore dimensions below 2 nm) structure are attractive next-generation materials for gas sorption, storage, catalysis and molecular level separations. Polymers of intrinsic microporosity (PIMs) represent a paradigm shift in conceptualizing molecular sieves from conventional ordered frameworks to disordered frameworks with heterogeneous distributions of microporosity. PIMs contain interconnected regions of micropores with high gas permeability but with a level of heterogeneity that compromises their molecular selectivity. Here we report controllable thermal oxidative crosslinking of PIMs by heat treatment in the presence of trace amounts of oxygen. The resulting covalently crosslinked networks are thermally and chemically stable, mechanically flexible and have remarkable selectivity at permeability that is three orders of magnitude higher than commercial polymeric membranes. This study demonstrates that controlled thermochemical reactions can delicately tune the topological structure of channels and pores within microporous polymers and their molecular sieving properties.

Collective osmotic shock in ordered materials

Osmotic shock in a vesicle or cell is the stress build-up and subsequent rupture of the phospholipid membrane that occurs when a relatively high concentration of salt is unable to cross the membrane and instead an inflow of water alleviates the salt concentration gradient. This is a well-known failure mechanism for cells and vesicles (for example, hypotonic shock) and metal alloys (for example, hydrogen embrittlement). We propose the concept of collective osmotic shock, whereby a coordinated explosive fracture resulting from multiplexing the singular effects of osmotic shock at discrete sites within an ordered material results in regular bicontinuous structures. The concept is demonstrated here using self-assembled block copolymer micelles, yet it is applicable to organized heterogeneous materials where a minority component can be selectively degraded and solvated whilst ensconced in a matrix capable of plastic deformation. We discuss the application of these self-supported, perforated multilayer materials in photonics, nanofiltration and optoelectronics.

Photo-oxidative enhancement of polymeric molecular sieve membranes

High-performance membranes are attractive for molecular-level separations in industrial-scale chemical, energy and environmental processes. The next-generation membranes for these processes are based on molecular sieving materials to simultaneously achieve high throughput and selectivity. Membranes made from polymeric molecular sieves such as polymers of intrinsic microporosity (pore size<2 nm) are especially interesting in being solution processable and highly permeable but currently have modest selectivity. Here we report photo-oxidative surface modification of membranes made of a polymer of intrinsic microporosity. The ultraviolet light field, localized to a near-surface domain, induces reactive ozone that collapses the microporous polymer framework. The rapid, near-surface densification results in asymmetric membranes with a superior selectivity in gas separation while maintaining an apparent permeability that is two orders of magnitude greater than commercially available polymeric membranes. The oxidative chain scission induced by ultraviolet irradiation also indicates the potential application of the polymer in photolithography technology.

Dopant-Free Hole-Transporting Materials for Stable and Efficient Perovskite Solar Cells

Molecularly engineered novel dopant-free hole-transporting materials for perovskite solar cells (PSCs) combined with mixed-perovskite (FAPbI3 )0.85 (MAPbBr3 )0.15 (MA: CH3 NH3+ , FA: NH=CHNH3+ ) that exhibit an excellent power conversion efficiency of 18.9% under AM 1.5 conditions are investigated. The mobilities of FA-CN, and TPA-CN are determined to be 1.2 × 10-4 cm2 V-1 s-1 and 1.1 × 10-4 cm2 V-1 s-1 , respectively. Exceptional stability up to 500 h is measured with the PSC based on FA-CN. Additionally, it is found that the maximum power output collected after 1300 h remained 65% of its initial value. This opens up new avenue for efficient and stable PSCs exploring new materials as alternatives to Spiro-OMeTAD.

Investigation of Ester- and Amide-Linker-Based Porous Organic Polymers for Carbon Dioxide Capture and Separation at Wide Temperatures and Pressures.

Organic compounds, such as covalent organic framework, metal-organic frameworks, and covalent organic polymers have been under investigation to replace the well-known amine-based solvent sorption technology of CO2 and introduce the most efficient and economical material for CO2 capture and storage. Various organic polymers having different function groups have been under investigation both for low and high pressure CO2 capture. However, search for a promising material to overcome the issues of lower selectivity, less capturing capacity, lower mass transfer coefficient and instability in materials performance at high pressure and various temperatures is still ongoing process. Herein, we report synthesis of six covalent organic polymers (COPs) and their CO2, N2, and CH4 adsorption performances at low and high pressures up to 200 bar. All the presented COPs materials were characterized by using elemental analysis method, Fourier transform infrared spectroscopy (FTIR) and solid state nuclear magnetic resonance (NMR) spectroscopy techniques. Physical properties of the materials such as surface areas, pore volume and pore size were determined through BET analysis at 77 K. All the materials were tested for CO2, CH4, and N2 adsorption using state of the art equipment, magnetic suspension balance (MSB). Results indicated that, amide based material i.e. COP-33 has the largest pore volume of 0.2 cm(2)/g which can capture up to the maximum of 1.44 mmol/g CO2 at room temperature and at pressure of 10 bar. However, at higher pressure of 200 bar and 308 K ester-based compound, that is, COP-35 adsorb as large as 144 mmol/g, which is the largest gas capturing capacity of any COPs material obtained so far. Importantly, single gas measurement based selectivity of COP-33 was comparatively better than all other COPs materials at all condition. Nevertheless, overall performance of COP-35 rate of adsorption and heat of adsorption has indicated that this material can be considered for further exploration as efficient and cheaply available solid sorbent material for CO2 capture and separation.

Adsorption and Desorption Equilibria of Nitrogen, Methane, Ethane, and Ethylene on Date-Pit Activated Carbon

Date pits were used to produce a highly porous activated carbon. The resulting date-pit activated carbon was used in a volumetric adsorption apparatus to measure the vapor-phase adsorption and desorption of nitrogen, methane, ethane, and ethylene over a wide range of pressure and at temperatures of (30, 45, and 60) °C. Being characterized with a relatively high surface area, the synthesized date-pit activated carbon exhibited a satisfactory capacity for adsorbing the various tested gases. However, the desorption of these gases exhibited a hysteresis phenomenon, especially at low temperatures. A Langmuir type model was proposed for fitting both the adsorption and the desorption data with hysteresis, and the corresponding isosteric heats of adsorption and desorption were estimated and compared.

Phase equilibria of the ternary system water + propionic acid + 2-butanol

Abstract Liquid–liquid equilibria for the ternary system water + propionic acid + 2-butanol was measured over a temperature range of 298 to 318 K. The results were used to estimate the interaction parameters between each of the three compounds for the nonrandom, two liquid (NRTL) equilibrium model as a function of temperature. The estimated interaction parameters were successfully used to predict the equilibrium compositions by the NRTL model. Based on this work, the distribution coefficients were also calculated and compared with the experimental values.

Thin, Flexible Supercapacitors Made from Carbon Nanofiber Electrodes Decorated at Room Temperature with Manganese Oxide Nanosheets

We report the fabrication and electrochemical performance of a flexible thin film supercapacitor with a novel nanostructured composite electrode. The electrode was prepared by in situ coprecipitation of two-dimensional (2D) MnO2 nanosheets at room temperature in the presence of carbon nanofibers (CNFs). The highest specific capacitance of 142 F/g was achieved for CNFs-MnO2 electrodes in sandwiched assembly with PVA-H4SiW12O40nH2O polyelectrolyte separator.