As primary feedstocks in the petrochemical industry, light olefins such as ethylene and propylene are mainly obtained from steam cracking of naphtha and short chain alkanes (ethane and propane). Due ...to their similar physical properties, the separations of olefins and paraffins—pivotal processes to meet the olefin purity requirement of downstream processing—are typically performed by highly energy‐intensive cryogenic distillation at low temperatures and high pressures. To reduce the energy input and save costs, adsorptive olefin/paraffin separations have been proposed as promising techniques to complement or even replace cryogenic distillation, and growing efforts have been devoted to developing advanced adsorbents to fulfill this challenging task. In this Review, a holistic view of olefin/paraffin separations is first provided by summarizing how different processes have been established to leverage the differences between olefins and paraffins for effective separations. Subsequently, recent advances in the development of porous materials for adsorptive olefin/paraffin separations are highlighted with an emphasis on different separation mechanisms. Last, a perspective on possible directions to push the limit of the research in this field is presented.
Adsorptive light olefin/paraffin separations facilitated by advanced porous materials such as zeolites and metal–organic frameworks are reviewed. Different separation mechanisms realized in these materials are highlighted, and constructive perspectives on future directions of the field are provided.
Metal–organic frameworks (MOFs) are a class of crystalline inorganic–organic hybrid materials that have demonstrated huge potential in gas separation due to their ultrahigh porosity, boundless ...chemical tunability, as well as surface functionality. Most gas separations realized in MOFs are under an equilibrium state and are dependent on the difference in thermodynamic affinities of gases to MOFs, whereas nonequilibrium separation such as kinetic and molecular sieving separation attracting growing attention in the past decade is achieved based on the difference in the size and diffusivity of gas molecules. In this perspective, we first discuss the pore size, temperature, and pressure effect on gas diffusion as well as nonequilibrium gas separation in MOFs. Second, we introduce current techniques reported to measure intracrystalline gas diffusivity. Third, we review recent progress in MOF-based nonequilibrium N2/O2 separation, CO2 capture, and hydrocarbon separation. In addition, we describe the hydrogen isotope separation based on kinetic quantum sieving in MOFs as a special scenario of kinetic gas separation. Lastly, we summarize general design strategies toward MOF-based nonequilibrium gas separation and propose several directions to advance the study in this exciting area.
In this paper we propose an approximation algorithm, which is called ADCMCST (algorithm with the minimum number of child nodes when the depth is restricted), to construct a tree network for ...homogeneous wireless sensor network, so as to reduce and balance the payload of each node, and consequently prolong the network lifetime. When the monitoring node obtains the neighbor graph, ADCMCST tries to find a tree topology with a minimum number of child nodes, and then broadcast the topology to every node, and finally a tree network is constructed. Simulation results show that ADCMCST could greatly reduce the topology formation time, and achieve good approximation results; when the compression ratio is less than 70 %, the network lifetime of ADCMCST will be larger than that of energy driven tree construction.
•FDMS is a much cheaper 3D printing method for metals.•Printing gaps in ‘Green parts’ are hard to eliminate.•Mechanical properties of FDMS metal parts are poorer than other processing methods.•FDMS ...metal parts are porosity and shrink during sintering process.
Conventional metal 3D printings are generally high energy consuming and expensive. As an alternative, Fused Deposition Modeling and Sintering (FDMS) was proposed for fast making metal parts at low energy consumption and low cost. Metal/polymer composite filament is printed by the printer based on Fused Deposition Modeling (FDM), and then debinding and sintering are conducted on the printed parts to form compact metal parts. Microstructural characteristics of the 316L/POM filament, printed parts and the final FDMS 316L parts are observed. Besides, the hardness, tensile properties, relative density, and part shrinkage were measured to understand the characteristics of the sintered FDMS 316L parts. Because the internal porosity and defects decrease the mechanical properties, the FDMS metal parts are suitable for applications without stringent requirements of strength, such as the functional products.
Traditional methods of generating vortex beams based on metasurfaces consist mainly in modulating propagation phase or geometric phase. Here, by introducing detour phase, we propose the construction ...of dual-polarized vortex beam generators in the form of metasurface and metagrating (MG). The phase is modulated through moving the position of meta-atoms instead of varying the geometrical parameters or rotating the unit cells. To use detour phase, two kinds of unit cells are designed to achieve specific diffraction order. Each unit can arbitrarily and independently adjust the operation frequency and diffraction angle of transverse electric (TE) and transverse magnetic (TM) polarizations. Two vortex beam generators are designed and fabricated with different topological charges carried by orthogonal polarizations. To demonstrate the ability to independently manipulate, two polarizations of the generator based on MG are designed in different frequency bands. Both the simulation and experimental results validate the proposed method, showing great potential for polarization division multiplexing in orbital angular momentum (OAM) communication systems.
Chiral binaphthyl enantiomers (Guest 1) were doped into commercial nematic liquid crystals (N-LCs, Host E7) to form chiral nematic liquid crystals (N*-LCs). The new ternary AIE-N*-LCs prepared by ...introducing four achiral AIE dyes (Guest 2) into N*-LCs can give rise to strong CPL responses with high luminescence dissymmetry factor (
g
em
) values of up to1.42.
AIE-N*-LCs prepared by supramolecular self-assembly between achiral AIE-active dyes and N*-LCs can exhibit highly strong CPL signals with
g
em
values in the range from 0.97 to 1.42. Most importantly, their emission wavelength can be tuned by changing the AIE-active dye.
Acetylene (C2H2) removal from ethylene (C2H4) is a crucial step in the production of polymer‐grade C2H4 but remains a daunting challenge because of the similar physicochemical properties of C2H2 and ...C2H4. Currently energy‐intensive cryogenic distillation processes are used to separate the two gases industrially. A robust ultramicroporous metal–organic framework (MOF), Ni3(pzdc)2(7 Hade)2, is reported for efficient C2H2/C2H4 separation. The MOF comprises hydrogen‐bonded linked one‐dimensional (1D) chains, and features high‐density open metal sites (2.7 nm−3) and electronegative oxygen and nitrogen sites arranged on the pore surface as cooperative binding sites. Theoretical calculations, in situ powder X‐ray diffraction and Fourier‐transform infrared spectroscopy revealed a synergistic adsorption mechanism. The MOF possesses S‐shaped 1D pore channels that efficiently trap trace C2H2 at 0.01 bar with a high C2H2 uptake of 60.6 cm3 cm−3 and C2H2/C2H4 selectivity.
Trace acetylene can be efficiently separated from ethylene via the synergistic effect of high‐density open metal and electronegative sites in an ultramicroporous metal–organic framework (MOF). The specific binding sites in the MOF afford an excellent acetylene uptake at 0.01 bar by maximizing the host–guest interactions.
Radiation therapy can potentially induce immunogenic cell death, thereby priming anti-tumor adaptive immune responses. However, radiation-induced systemic immune responses are very rare and ...insufficient to meet clinical needs. Here, we demonstrate a synergetic strategy for boosting radiation-induced immunogenic cell death by constructing gadolinium-hemin based nanoscale coordination polymers to simultaneously perform X-ray deposition and glutathione depletion. Subsequently, immunogenic cell death is induced by sensitized radiation to potentiate checkpoint blockade immunotherapies against primary and metastatic tumors. In conclusion, nanoscale coordination polymers-sensitized radiation therapy exhibits biocompatibility and therapeutic efficacy in preclinical cancer models, and has the potential for further application in cancer radio-immunotherapy.
Surmounting the inhomogeniety issue of gas sensors and realizing their reproducible ppb‐level gas sensing are highly desirable for widespread deployments of sensors to build networks in applications ...of industrial safety and indoor/outdoor air quality monitoring. Herein, a strategy is proposed to substantially improve the surface homogeneity of sensing materials and gas sensing performance via chip‐level pyrolysis of as‐grown ZIF‐L (ZIF stands for zeolitic imidazolate framework) films to porous and hierarchical zinc oxide (ZnO) nanosheets. A novel approach to generate adjustable oxygen vacancies is demonstrated, through which the electronic structure of sensing materials can be fine‐tuned. Their presence is thoroughly verified by various techniques. The sensing results demonstrate that the resultant oxygen vacancy‐abundant ZnO nanosheets exhibit significantly enhanced sensitivity and shortened response time toward ppb‐level carbon monoxide (CO) and volatile organic compounds encompassing 1,3‐butadiene, toluene, and tetrachloroethylene, which can be ascribed to several reasons including unpaired electrons, consequent bandgap narrowing, increased specific surface area, and hierarchical micro–mesoporous structures. This facile approach sheds light on the rational design of sensing materials via defect engineering, and can facilitate the mass production, commercialization, and large‐scale deployments of sensors with controllable morphology and superior sensing performance targeted for ultratrace gas detection.
A facile approach for designing sensing materials via rational defect engineering to tune the electronic structure of on‐chip MOF‐derived hierarchical ZnOs and thus sensing properties is proposed. The resultant homogeneous ZnO layer with abundant oxygen vacancies exhibits significantly enhanced sensitivity and short response time toward ppb‐level carbon monoxide and volatile organic compounds.
Isoreticular functionalization is a well‐elucidated strategy for pore environment tuning and the basis of gas separation performance in extended frameworks. The extension of this approach to discrete ...porous molecules such as metal‐organic cages (MOCs) is conceptually straightforward but hindered by synthetic complications, especially stability concerns. We report the successful isoreticular functionalization of a zirconium MOC with tetrazole moiety by bottom‐up synthesis. The title compound (ZrT‐1‐tetrazol) shows promising C2H2/CO2 and C2H2/C2H4 separation performance, as demonstrated by adsorption isotherms, breakthrough experiments, and density functional theory calculations. The design analogy between MOFs and highly stable MOCs may guide the synthesis of novel porous materials for challenging separation applications.
We report the use of isoreticular chemistry to synthesize a tetrazole‐functionalized metal‐organic cage (ZrT‐1‐tetrazol) with the same structure of ZrT‐1 and ZrT‐1‐NH2. The adsorption capacity of ZrT‐1‐tetrazol for C2H2 increases by 130 % (298 K) compared with ZrT‐1‐NH2, and it exhibits promising C2H2/CO2 and C2H2/C2H4 separation performance.
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