Flexibility On-Demand: Multivariate 3D Covalent Organic Frameworks.

Dynamic 3D covalent organic frameworks (dynaCOFs) have shown concerted structural transformation and responses upon adaptive guest adsorption. The multivariate (MTV) strategy incorporating multiple functionalities within a backbone is attractive for tuning the framework flexibility and dynamic responses. However, a major synthetic challenge arises from the different chemical reactivities of linkers usually resulting in phase separation.

User Pairing for Delay-Limited NOMA-Based Satellite Networks with Deep Reinforcement Learning.

In this paper, we investigate a user pairing problem in power domain non-orthogonal multiple access (NOMA) scheme-aided satellite networks. In the considered scenario, different satellite applications are assumed with various delay quality-of-service (QoS) requirements, and the concept of effective capacity is employed to characterize the effect of delay QoS limitations on achieved performance. Based on this, our objective was to select users to form a NOMA user pair and utilize resource efficiently.

Multivariate Metal-Organic Frameworks Prepared by Simultaneous Metal/Ligand Exchange for Enhanced C2-C3 Selective Recovery from Natural Gas.

Recovering light alkanes from natural gas is a critical but challenging process in petrochemical production. Herein, we propose a postmodification strategy via simultaneous metal/ligand exchange to prepare multivariate metal-organic frameworks with enhanced capacity and selectivity of ethane (CH) and propane (CH) for their recovery from natural gas with methane (CH) as the primary component. By utilizing the Kuratowski-type secondary building unit of CFA-1 as a scaffold, namely, {Zn(OAc)}, the Zn metal ions and OAc ligands were simultaneously exchanged by other transition metal ions and halogen ligands under mild conditions.

Synthesis of hierarchical porous carbon with high surface area by chemical activation of (NH)CO modified hydrochar for chlorobenzene adsorption.

In this work, hydrothermal technique combined with KOH activation were employed to develop a series of porous carbons (NPCK-x) using tobacco stem as a low-cost carbon source and (NH)CO as a novel nitrogen-doping agent. Physicochemical properties of NPCK-x were characterized by Brunauer-Emmett-Teller, field emission scanning electron microscopy, X-ray diffraction, Raman microscope, elemental analysis, and X-ray photoelectron spectroscopy. Results showed that the NPCK-x samples possessed large surface areas (maximum: 2875 m/g), hierarchical porous structures, and high degree of disorder.

Flexible Humidity Sensors Based on Multidimensional Titanium Dioxide/Cellulose Nanocrystals Composite Film.

A humidity sensor is a crucial device in daily life; therefore, in the present study, a novel humidity sensor was designed to increase its specific surface area to improve its humid sensing capacity and conductivity. Titanium dioxide nanoparticles (TiNP) consisting of zero-dimensional nanospheres and one-dimensional nanotubes were prepared by anodic oxidation. Rod-shaped cellulose nanocrystals (CNCs) with average length and diameter of 60 nm and 800 nm, respectively, were obtained by enzymatic hydrolysis and high pressure homogenization.

Assessment of multiple environmental factors on the adsorptive and photocatalytic removal of gaseous formaldehyde by a nano-TiO colloid: Experimental and simulation studies.

Environmental factors affecting the photocatalytic oxidation of volatile organic compounds (VOCs) have previously been studied experimentally, but there are few theoretical studies, especially those on surface intermolecular forces. Because of this, it is unclear how multiple coexisting factors impact photocatalytic processes. Herein, comprehensive multi-factorial impact mechanisms of the photocatalytic oxidation of formaldehyde were assessed using experiments and density functional theory simulations.

Photo-catalytic degradation of mixed gaseous HCHO and CH in paper mills: Experimental and theoretical study on the adsorption behavior simulation and catalytic reaction mechanism.

VOCs in paper mills have severely exceeded the emission standards and their photo-catalytic degradations should focus on the experimental and theoretical studies. This work used TiO colloid as catalyst to study the photo-catalytic degradations of mixed HCHO and CH at five mixing ratios. The adsorption behaviors of pure forms and mixtures on the TiO (101) surface were simulated using density functional theory (DFT), and their catalytic reaction mechanisms were also analyzed.

Templated fabrication of hierarchically porous metal-organic frameworks and simulation of crystal growth.

Hierarchically porous metal-organic frameworks (MOFs) have recently emerged as a novel crystalline hybrid material with tunable porosity. Many efforts have been made to develop hierarchically porous MOFs, yet their low-energy fabrication remains a challenge and the underlying mechanism is still unknown. In this study, the rapid fabrication of two hierarchically porous MOFs (Cu-BTC and ZIF-8) was carried out at room temperature and ambient pressure for 10 min using a novel surfactant as the template in a (Cu, Zn) hydroxy double salt (HDS) solution, where the (Cu, Zn) HDS accelerated the nucleation of crystals and the anionic surfactants served as templates to fabricate mesopores and macropores.

Hierarchically porous metal-organic frameworks: rapid synthesis and enhanced gas storage.

Large pore sizes, high pore volumes, facile synthesis conditions, and high space-time yields are recognized as four crucial criteria in the fabrication of metal-organic frameworks (MOFs). However, these four objectives are rarely realized together. Herein, we have developed a simple and versatile method that employs 1,4-butanediamine (BTDM) as a template for rapidly fabricating four stable hierarchically porous MOFs (H-MOFs), including HKUST-1, ZIF-8, ZIF-67, and ZIF-90.

Unusual Moisture-Enhanced CO Capture within Microporous PCN-250 Frameworks.

Developing metal-organic frameworks (MOFs) with moisture-resistant feature or moisture-enhanced adsorption is challenging for the practical CO capture under humid conditions. In this work, under humid conditions, the CO adsorption behaviors of two iron-based MOF materials, PCN-250(Fe) and PCN-250(FeCo), were investigated. An interesting phenomenon is observed that the two materials demonstrate an unusual moisture-enhanced adsorption of CO.

In Situ Fabrication of Hierarchical MTW Zeolite via Nanoparticle Assembly by a Tailored Simple Organic Molecule.

Amphiphilic surfactants are widely used as templates to synthesize hierarchically structured zeolites due to their multiple functions; however, piloting such new dual-functional templates is limited by their time-consuming nature and high cost. Herein, a simple organic molecule, without a long hydrophobic alkyl chain, was tailored from a gemini-type, poly-quaternary ammonium surfactant, and effectively used as a dual-porogenic template to synthesize hierarchical MTW zeolite. Upon a range of synthesis parameter optimizations, our detailed characterization suggested that the hierarchical MTW zeolite would completely crystallize within 36 hours from the surface to the inside of quasi-spherical particles through in situ consumption of amorphous silicon and aluminum species; much faster than most of the hierarchical MTW zeolites generated by conventional methods.

Selective Adsorption of Ethane over Ethylene in PCN-245: Impacts of Interpenetrated Adsorbent.

The separation of ethane from ethylene using cryogenic distillation is an energy-intensive process in the industry. With lower energetic consumption, the adsorption technology provides the opportunities for developing the industry with economic sustainability. We report an iron-based metal-organic framework PCN-245 with interpenetrated structures as an ethane-selective adsorbent for ethylene/ethane separation.

In Situ Assembly of Nanoparticles into Hierarchical Beta Zeolite with Tailored Simple Organic Molecule.

A hierarchically structured beta zeolite with intercrystalline mesopores was successfully synthesized via in situ assembly of nanoparticles by employing a simple organic molecule N-p-N, tailored from polyquaternium surfactant, with no hydrophobic long chain. The generated samples were studied by using powder X-ray diffraction (XRD) and nitrogen adsorption/desorption isotherms. Computer simulation, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) technologies were also used.

Tailoring Hierarchical Zeolites with Designed Cationic Surfactants and Their High Catalytic Performance.

Three hierarchical porous zeolites (H-*BEA, H-MTW, and H-*MRE) were successfully synthesized with the assistance of designed cationic surfactants under hydrothermal synthesis conditions. The as-synthesized zeolite samples can be easily regulated by changing the number of long hydrophobic n-alkyl chains. Also, we investigated the relationship between the length of the surfactant and the formation of the microporous structure of the zeolite.

Adsorptive Separation of Methanol-Acetone on Isostructural Series of Metal-Organic Frameworks M-BTC (M = Ti, Fe, Cu, Co, Ru, Mo): A Computational Study of Adsorption Mechanisms and Metal-Substitution Impacts.

The adsorptive separation properties of M-BTC isostructural series (M = Ti, Fe, Cu, Co, Ru, Mo) for methanol-acetone mixtures were investigated by using various computational procedures of grand canonical Monte Carlo simulations (GCMC), density functional theory (DFT), and ideal adsorbed solution theory (IAST), following with comprehensive understanding of adsorbate-metal interactions on the adsorptive separation behaviors. The obtained results showed that the single component adsorptions were driven by adsorbate-framework interactions at low pressures and by framework structures at high pressures, among which the mass effects, electrostatics, and geometric accessibility of the metal sites also played roles. In the case of methanol-acetone separation, the selectivity of methanol on M-BTCs decreased with rising pressures due to the pressure-dependent separation mechanisms: the cooperative effects between methanol and acetone hindered the separation at low pressures, whereas the competitive effects of acetone further resulted in the lower selectivity at high pressures.

Effective ligand functionalization of zirconium-based metal-organic frameworks for the adsorption and separation of benzene and toluene: a multiscale computational study.

The adsorption and separation properties of benzene and toluene on the zirconium-based frameworks UiO-66, -67, -68, and their functional analogues UiO-Phe and UiO-Me2 were studied using grand canonical Monte Carlo simulations, density functional theory, and ideal adsorbed solution theory. Remarkable higher adsorption uptakes of benzene and toluene at low pressures on UiO-Phe and -Me2 were found compared to their parent framework UiO-67. It can be ascribed to the presence of functional groups (aromatic rings and methyl groups) that significantly intensified the adsorption, majorly by reducing the effective pore size and increasing the interaction strength with the adsorbates.

Molecular simulation and experimental studies of a mesoporous ZSM-5 type molecular sieve.

The mesoporous zeolite is a novel porous material possessing mesopores as well as the inherent micropores of zeolites. This material can exhibit the dual merits of two different pore structures and enable zeolites to have maximum structural functions. During the past few decades, various synthetic strategies have been well developed.

Effects of loading different metal ions on an activated carbon on the desorption activation energy of dichloromethane/trichloromethane.

The effects of loading Fe(3+), Mg(2+), Cu(2+) or Ag(+) on activated carbons (ACs) on interaction of the carbon surfaces with dichloromethane (DCM) and trichloromethane (TCM) were investigated. Temperature-programmed desorption (TPD) experiments were conducted to measure the desorption activation energy of DCM/TCM on the ACs separately doped with ions Fe(3+), Mg(2+), Cu(2+) and Ag(+). The absolute hardness and electronegativity of DCM and TCM were estimated on the basis of density functional theory.

Synthesis and properties of the anti and syn isomers of dibenzothieno[b,d]pyrrole.

A novel type of anti and syn isomers of a pentacyclic compound consisting of two thiophene rings and one pyrrole ring were efficiently synthesized from benzo[b]thiophene, and the anti isomer exhibits better charge transport and OFET properties compared with the syn isomer and its N-hexyl substitution.

Effect of ultrasound on desorption kinetics of phenol from polymeric resin.

This work mainly involves the study of desorption kinetics of phenol from polymeric resins under the influence of an ultrasound field. A new phase equilibrium-kinetics model (PEKM), for estimation of diffusion coefficient was proposed, kinetic experiments of phenol desorption on NKA-II resin in the presence and the absence of ultrasound were separately conducted, and diffusion coefficients of phenol within an adsorbent particle were estimated by means of proposed PEKM. Results showed that the use of ultrasound could enhance the diffusion of phenol within the resin.

Influence of the microporosity and surface chemistry of polymeric resins on adsorptive properties toward phenol.

In this work, the effects of the microporosity and chemical surface of polymeric adsorbents on adsorptive properties of phenol were investigated. Textural parameters of four kinds of polymeric resins, namely AB-8, D4006, NKA-II and D16 resin, were separately measured by ASAP 2010. The surface chemistry of these polymeric resins was determined by means of inverse gas chromatography (IGC) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS).