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Light olefins (ethylene, propylene, and 1,3-butadiene) are widely used as building blocks in the petrochemical industry and for the fabrication of everyday products. Developing energy cost-efficient porous materials for the separation of light olefins is fundamentally and industrially important. Metal–organic frameworks (MOFs), representing a novel class of porous materials, possess unique pore structures, endowing them with exceptional porosity, tunable pore sizes, and facile functionalization. These features permit distinct host–guest interactions and/or sieving effects, allowing the separation of molecules in an energy-efficient manner. However, some critical factors, such as large-scale production and fabrication into shaped forms need to be addressed for real industrial separations. To solve these issues, many novel approaches for synthesizing and shaping MOFs have recently been developed. In this review, we summarize and highlight recent advances in the realm of gas separation using MOFs as adsorbents, covering the progress made in improving the key features of MOFs that are necessary for their real-world applications, and opening a broader perspective on the current status of this field and its challenges.

Methane (CH

Ferroelectric domain wall memories have been proposed as a promising candidate for nonvolatile memories, given their intriguing advantages including low energy consumption and high-density integration. Perovskite oxides possess superior ferroelectric prosperities but perovskite-based domain wall memory integrated on silicon has rarely been reported due to the technical challenges in the sample preparation. Here, we demonstrate a domain wall memory prototype utilizing freestanding BaTiO3 membranes transferred onto silicon. While as-grown BTO films on (001) SrTiO3 substrate are purely c-axis polarized, we find they exhibit distinct in-plane multidomain structures after released from the substrate and integrated onto silicon due to the collective effects from depolarizing field and strain relaxation. Based on the strong in-plane ferroelectricity, conductive domain walls with reading currents reaching 2 nA are observed and can be created artificially, highlighting the great potential of the integration of perovskite oxides with silicon for ferroelectric domain wall memories.

Metal–organic frameworks (MOFs) with open metal sites have attracted lots of attention because of their high binding energy for adsorbates. MIL-100(Cr) is one of the potential MOFs for challenging ...

The exploration of electrocatalysts with high oxygen evolution reaction (OER) activity is highly desirable and remains a significant challenge. Transition metal carbides (TMCs) have been investigated as remarkable hydrogen evolution reaction (HER) electrocatalysts but few used as oxygen evolution reaction (OER) electrocatalysts. Herein, a Co doped Ni3C/Ni uniformly dispersed in a graphitic carbon matrix was prepared by pyrolysis of a metal organic framework (Co/Ni-MOF) under a flow of Ar/H2 at 350 °C, and Ni3C/Ni@C was also prepared for comparison. The various characterization techniques confirmed the successful preparation of the heteroatom doped TMCs-based catalysts by pyrolysis of MOFs. Co doped Ni3C/Ni@C exhibited superior electrocatalytic properties for OER. For example, Co–Ni3C/Ni@C depicts a lower overpotential and smaller Tafel slope than Ni3C/Ni@C and IrO2 during the OER in 1 M KOH solution, additionally, it shows a higher active surface area than Ni3C/Ni@C. The outstanding electrocatalytic performance of Co-doped Ni3C/Ni@C in the OER was mainly ascribed to the synergistic effect of the Co and Ni3C/Ni active sites.

Samples of methane molecules grade diameter channel CHA-type molecular sieves (Chabazite-K, SAPO-34 and SSZ-13) were investigated using the adsorption separation of CH4/N2 mixtures. The isotherms recorded for CH4 and N2 follow a typical type-Ι behavior, which were fitted well with the Sips model (R2 > 0.999) and the selectivity was calculated using IAST theory. The results reveal that Chabazite-K has the highest selectivity (SCH4/N2 = 5.5). SSZ-13 has the largest capacity, which can adsorb up to a maximum of 30.957 cm3·g−1 (STP) of CH4, due to it having the largest pore volume and surface area, but the lowest selectivity (SCH4/N2 = 2.5). From the breakthrough test, we can conclude that SSZ-13 may be a suitable candidate for the recovery of CH4 from low concentration methane (CH4 50%) due to its higher selectivity.

We report on the atomic hydrogen annealing to in situ manipulate the electronic structures in semimetal SrIrO3 films. Carriers are found to be effectively doped into epitaxial SrIrO3 films by atomic hydrogen annealing without degrading the lattice structure, as revealed by transport and structural measurements. Using angle-resolved photoemission spectroscopy, the low-lying hole bands exhibit a nearly rigid band shift toward the higher binding energy upon atomic hydrogen annealing, which can be further restored by the ozone annealing. Unlike the typical in situ alkali-metal surface doping method, our atomic-hydrogen-treated SrIrO3 films are stable in air, which warrants ex situ characterizations. Our work shows a reversible and effective in situ carrier doping method to explore exotic phases in strongly correlated systems, such as the potential superconductivity in iridates.

The removal of low concentration N

It is a big challenge to separate N2O from CO2 using adsorption because they have similar physical properties. The Fe3+-F- site in MIL-100Fe transforms to an unsaturated Fe2+ site under high-temperature activation (300 °C), and the target sorbent MIL-100Fe-300 exhibits the biggest difference in CO2 and N2O adsorption capacity, and the selectivity of N2O/CO2 (50%/50%) is up to 3.00 at 298 K. According to DFT calculations, the original Fe3+-F- site has strong interaction with CO2, but the open Fe2+ site has a stronger interaction with N2O. Through a breakthrough experiment, it was confirmed that MIL-100Fe-300 has the best N2O/CO2 separation performance, making it potentially a useful material in industry.

Acetylene, an important petrochemical feedstock, is the starting chemical to produce many polymer products. Separating C2H2 from its by-product mixtures is still an energy-consuming process and remains challenging. Here, we present a metal-organic framework[Zn2(bpy)(btec)], with a desirable pore geometry and stable framework, which demonstrated a high separation performance of C2H2 from simulated mixtures. With the desirable pore dimension and hydrogen bonding sites, Zn2(bpy)(btec) shows by far the both highest C2H2/C2H4 and C2H2/CO2 uptake ratios, very high adsorption selectivities and moderately C2H2 uptake of 93.5 cm3/cm3 under 298 K and 1 atm. Not only straightforwardly produced high purity of C2H4, but also recovered high purity of C2H2 (>98% in the regeneration process (>92% recovery). More notably, Zn2(bpy)(btec) can be straightforwardly synthesized at a large scale under environmentally friendly conditions, and its good water/chemical stability, thermostability, and cyclic stability highlight the promise of this molecular sieving material for industrial C2H2 separation.

To isolate iron sulphide and reduce coke adhesion reactions that occur on the surface of a delayed coking furnace, a SiO

Acetylene, an important petrochemical feedstock, is the starting chemical to produce many polymer products. Separating C2H2 from its by-product mixtures is still an energy-consuming process and remains challenging. Here, we present a metal-organic framework[Zn2(bpy)(btec)], with a desirable pore geometry and highly stable framework, which demonstrated a high separation performance of C2H2 from simulated mixtures. With the desirable pore dimension and hydrogen bonding sites, Zn2(bpy)(btec) shows by far the both highest C2H2/CO2 and C2H2/CO2 uptake ratios, very high adsorption selectivities and moderately C2H2 uptake of 93.5 cm3•cm−3 under 298 K and 1 atm. Not only straightforwardly produced high purity of C2H4, but also recovered high purity of C2H2 (>98%) in the regeneration process (>92% recovery). More notably, Zn2(bpy)(btec) can be straightforwardly synthesized at a large scale under environmentally friendly conditions, and its good water/chemical stability, thermostability, and cyclic stability highlight the promise of this molecular sieving material for industrial C2H2 separation.

NH3 is the most important gaseous alkaline pollutant, which when accumulated at high concentrations can have a serious impact on animal and human health. More importantly, NH3 emissions will react ...

Separation of ethane from ethylene is a very important but challenging process in the petrochemical industry. Finding an alternative method would reduce the energy needed to make 170 million tons of ethylene manufactured worldwide each year. Adsorptive separation using C(2)H(6)-selective porous materials to directly produce high-purity C(2)H(4) is more energy-efficient. We herein report the “reversed C(2)H(6)/C(2)H(4) adsorption” in a metal–organic framework Cr-BTC via the introduction of oxygen on its open metal sites. The oxidized Cr-BTC(O(2)) can bind C(2)H(6) over C(2)H(4) through the active Cr-superoxo sites, which was elucidated by the gas sorption isotherms and density functional theory calculations. This material thus exhibits a good performance for the separation of 50/50 C(2)H(6)/C(2)H(4) mixtures to produce 99.99% pure C(2)H(4) in a single separation operation.

Separating ethane (C2H6) from ethylene (C2H4) using ethane-selective adsorbents to replace energy-intensive cryogenic distillation technology is an important energy-saving method in the petrochemical industry to obtain high purity C2H4. Limited to the low separation efficiency in current commercial materials, it is very urgent and promising to fabricate such alkane selective adsorbents using cheap ligands and simple synthesis methods, which have characteristics such as stable structure, high C2H6 uptake, and adsorption selectivity. In this work, we have used one of the cheapest ligands (terephthalic acid, H2BDC) to prepare Cu(BDC)(DMF) via a simple and easy-to-scale up solvothermal method. The activated Cu(BDC) exposed diamond-shaped one-dimensional pores form a stronger affinity with C2H6 than C2H4 through the double function of C-H∙∙∙π interactions and C-H∙∙∙O hydrogen bonds. Benefiting from the difference in these interactions, Cu(BDC) exhibited a higher adsorption capacity of C2H6 (51.5 cm3/g) compared to C2H4 (45.1 cm3/g) at 1 bar and 298 K, which resulted in high adsorption selectivity (2.0) for the C2H6/C2H4 mixture (50/50, v/v). Breakthrough experiments indicated that Cu(BDC) successfully achieved the removal of C2H6 from C2H6/C2H4 (50/50 and 10/90, v/v) mixtures to obtain high purity C2H4 (> 99.99%) using a one-step separation process. When compared with the benchmark materials, Fe2(O2)(dobdc) and NIIC-20, Cu(BDC) had the advantages of much lower preparation cost and enhanced structural stability. These comprehensive properties indicated that Cu(BDC) with a commercially viable price and synthesis process, could be potentially used for the C2H6 removal step during the production of high purity C2H4.

Natural gas purification by economic and low-energy adsorptive separation processes is important. However, as a difficult global problem, N2 removal from N2/CH4 mixtures is challenging because of their similar physical properties. In this study, the separation of N2/CH4 by Cr-metal–organic frameworks (MOFs) (MIL-100Cr, MIL-101Cr and TYUT-96Cr) with various open Cr site densities was studied. Gas sorption isotherms showed that TYUT-96Cr exhibited the highest N2/CH4 uptake ratio (13.67 at 0.01 bar and 298 K) of the selected Cr-MOFs, which was consistent with the highest density of Cr (III) sites. This material provided the highest CH4 productivity (0.716 mmol/cm3) per cycle for N2 removal from a 5:95 N2/CH4 mixture to produce 99.99% pure CH4, as shown by the breakthrough experiments. Pressure-swing adsorption simulations indicated that, by a two-bed six-step method, pristine 95% methane was enriched to 98.9% by TYUT-96Cr. The largest CH4 productivity, high breakthrough selectivity and thermal stability of TYUT-96Cr among the Cr-MOFs, made it a promising adsorbent in trace N2 removal for practical industrial application.

Nitrous oxide (N2O) is considered as the third most important greenhouse gas after carbon dioxide and methane and needs to be removed from air. Herein, we reported the metal–organic framework MIL-100Cr with open Cr sites for record N2O capture capacities of 5.78 mmol g−1 at 298 K and 8.25 mmol g−1 at 273 K, respectively. DFT calculations showed that the static binding energy of N2O on the open-Cr site is notably higher than that of N2, 72.5 kJ mol−1vs. 51.6 kJ mol−1, which enforces MIL-100Cr to exhibit extremely high N2O/N2 ideal adsorbed solution theory (IAST) gas separation selectivity up to 1000.

It is very challenging to prepare biomass-derived porous carbons with well-confined ultramicropores. Traditionally, biomass-derived carbons, via a chemical activation process, possess wide pore size distributions from micropores to macropores. Outstanding BET surface area of 2676 ± 107 m2 g–1 was obtained with excellent CO2 uptake of 6.15 and 2.26 mmol g–1 under 1 and 0.15 bar at 273 K. Furthermore, the outstanding CO2/N2, CO2/CH4, and CH4/N2 selectivities of 43.5, 7.4, and 5.9 were obtained on an OTS-1-550 at 298 K and 1 bar. The pore size effect on CO2 capture and gas-separation performance was carefully investigated, indicating that the ultramicropores (

For the capture of CO2 from flue gas and decarbonization of natural gas streams, an ideal adsorbent should have a high selectivity for CO2 over N2 and CH4. In this work, through adjusting the proportions of extra-framework K+ and Cs+ cations and varying the Si/Al ratios of the zeolite ZK-5, the small “molecular gate” adsorbent ZK-5-n-K has been prepared. An increase in the number of K+ cations prevents the ingress of the larger molecules CH4 and N2, while allowing entry of the smaller CO2; the net result is that CO2 capture from CH4 or N2 is achieved with unusually high selectivity, of the order of 1 × 105. Grand canonical Monte Carlo simulations show that the extra-framework K+ and Cs+ cations are positioned at different locations in the ZK-5; K+ locates near the 8-ring window, whereas Cs+ resides in the interior regions. The separation performances of 12 different K+- and Cs+-doped ZK-5 structures (with four different Si/Al ratios of 3.17, 3.36, 3.46, and 3.57) have been investigated. Transient breakthrough simulations have been used to quantify the CO2 capture performances in four sets of separations: 30%/70%, 5%/95%, and 2%/98% CO2/CH4 mixtures at a total pressure of 1 MPa, and a 15%/85% CO2/N2 mixture at a total pressure of 100 kPa. In all cases, the selectivities were sufficiently high to ensure that the separation performance was primarily governed by the CO2 uptake capacity. The overall conclusion to be drawn from this work is that ZK-5 is a suitable adsorbent for the decarbonization of natural gas.

It is notably challenging to fabricate controllable heteroatom-doped porous carbons for both highly effective mixed-gas separation and supercapacitor electrodes. In this work, novel algae-derived nitrogen-containing porous carbons were prepared as bifunctional materials. The pore structure of obtained carbons could be easily tailored by altering activation temperature or porogen/biomass ratio. The as-prepared porous carbon has a very high specific surface area of 1538.7 m2 g−1 and a large pore volume of 0.99 cm3 g−1 with a high N content of 2.77 wt%. As a solid-state adsorbent, the algae-derived carbon has an excellent CO2 adsorption capacity of 5.7 and 3.9 mmol g−1 at 273 and 298 K, respectively. The extraordinarily high CO2/N2, CO2/CH4, and CH4/N2 selectivity are demonstrated by the ideal adsorption solution theory (IAST) calculation and dynamic adsorption breakthrough experiments. As an electroactive material, the porous carbon exhibits outstanding capacitive performance in 6 M KOH aqueous electrolyte, with the specific capacitance of 287.7 and 190.0 F g−1 at 0.2 A g−1 in a three- and two-electrode system, respectively. Furthermore, the obtained carbon shows outstanding rate capability of 79.3% at 10 A g−1 and unprecedented cycling stability with 98% capacitance retention at 10 A g−1 after 8000 cycles as coin cell. This report introduces a biomass-derived and low-cost pathway to design porous carbon materials for efficient solid adsorbents and supercapacitive electrode materials.

Two types of ultra-high silica silicalite-1 (2000–4400 SiO2/Al2O3) were prepared using a seed crystal synthesis method; silicalite-1-M, which is microporous (0.5 nm) and silicalite-1-H, which is hierarchical porous (0.5 nm and 10–15 nm). From the experimental results, silicalite-1-H/M have almost the same adsorption isotherms for CO2, CH4, C2H6 and N2, surface area and equilibrium adsorption selectivity, however, silicalite-1-H has a shorter adsorption equilibrium time when compared with silicalite-1-M at a given pressure, which shows a mass transfer enhancement phenomenon due to its mesoporous structure. A mixed gas breakthrough test and simulation was carried out to verify the mass transfer upgrade theory to determine whether the material could be applied for adsorption separation. Interestingly, their performances on the breakthrough experiment were different; silicalite-1-H has a shorter breakthrough time for CO2, CH4, C2H6 and N2 when compared with silicalite-1-M. All the experiment data are consistent with the simulation results. A variety of flow rates were used to investigate and compare the breakthrough time and hold time, and the separation efficiency of CO2/CH4, CH4/N2 and CH4/C2H6 was improved based on the use of the hierarchical porous sorbent over a certain flow rate range.

Metal-organic frameworks (MOFs) have been rapidly developed in the fields of gas adsorption and storage, but are unsatisfactory in NH 3 adsorption due to their unstable structures. Considering NH 3 is both a toxic gas and the only carbon-free chemical energy carrier, MOFs exhibit great prospects for the adsorption and storage of NH 3 due to their advantages of structural diversity, modifiable structures and high surface area. In this work, we have researched, in detail, the structural characteristics, stability and NH 3 adsorption properties of MIL-53, NH 2 -MIL-53, MIL-100 and MIL-101. In addition, the NH 3 adsorption sites have been investigated using Grand canonical Monte Carlo simulations. The results showed that MIL-100 and MIL-101 have a large NH 3 uptake of 8 mmol/g and 10 mmol/g, respectively, and that the modified amino functional groups improve the NH 3 adsorption capacity in NH 2 -MIL-53. More importantly, the four MIL materials have reusable NH 3 uptake and excellent NH 3 (and NH 3 /H 2 O) stability, and are promising materials for NH 3 adsorption.

Two environmentally friendly and efficient synthesis methods, NH3-assisted synthesis and solvent-evaporated conversion, have been developed for the synthesis of a series of M(NA)2 (M = Zn, Co, Cu, Cd; NA = nicotinate) flexible MOFs. The two-dimensional M(NA)2 (M = Zn, Co) and three-dimensional M(NA)2 (M = Cu, Cd) materials exhibit peculiar structural transformation. These frameworks can be obtained from dehydration of M(NA)2(H2O)4 (M = Zn, Co, Cu, Cd) which are zero-dimensional supramolecular structures. Interestingly, the structural transformation of M(NA)2 (M = Zn, Co, Cd) is reversible after liquid water adsorption. Due to the flexible structure of these MOFs, they exhibit abnormal NH3 adsorption properties. The two-dimensional Zn(NA)2 shows a gate-opening behavior for NH3 adsorption. Its layers opened at a pressure of 0.22 bar in the first cycle, resulting in a two-step NH3 uptake with a capacity of 10.2 mmol g−1 at 1 bar. The gate-opening pressure shifted to a lower value with cycles. Co(NA)2 has a huge NH3 uptake of 17.5 mmol g−1, which is top-ranking among the reported values. For the NH3 adsorption over Cu(NA)2 and Cd(NA)2, the adsorption rates increase and adsorption equilibrium is achieved faster after three cycles. Their maximum capacity at 1 bar is 13.4 and 6 mmol g−1, respectively. More importantly, all MOFs can be regenerated under vacuum and heating conditions of 150 °C for 70 min, and they all retained the capacity. The advantages of environmentally friendly synthesis, large adsorption capacity, and regenerable properties indicate that M(NA)2 (M = Zn, Co, Cu) are promising candidates for NH3 adsorption.

MIL-100(Cr), as a typical metal organic framework (MOF) possesses a great potential application for N2 removal from CH4 by physical adsorption, but the commonly used preparation process at present is time-consuming (96 h) and environmentally unfriendly (HF-needed). We developed a novel synthesis method which is able to prepare MIL-100(Cr) via steam-assisted conversion and avoids the usage of HF with a curtate reaction time (9 h) and excellent yield (96%), a higher selectivity of N2 from CH4. Obviously, this method is advantageous and suitable for green large-scale production of MIL-100 (Cr).

The Si/Al ratio in zeolite will be altered and the porous structure will be diluted by the traditional silica/aluminum-based binder in the granulation process. Here, a novel zeolite/activated carbon monolith (Z/AC) was prepared by adding coal-tar pitch in silicalite-1 (Si/Al greater than 400), where the pure silica characteristic is well maintained and the coal-tar pitch transforms to porous carbon with a uniform pore structure, in comparison, the aluminum-based bonded silicalite-1 pellet (ABSP) shows a much lower Si/Al ratio of 4.1. As a result, the Z/AC-600 monolith demonstrates a competitive CH4 adsorption capacity of 23.45 cm3/g, outperforming silicalite-1 powder and ABSP pellet, and the CH4/N2 selectivity is higher than 4.0 at 298 K and 1 bar. The gas-mixture breakthrough experiments demonstrated that Z/AC-600 can effectively separate the CH4/N2 mixtures (20/80 and 50/50; v/v) with dynamic selectivity of 4.2 and 3.9, respectively. Pressure swing adsorption (PSA) simulations further indicate that, by one step enrichment, pristine 50% methane can be enriched to 80% with a recovery of 85%.

The slight differences between ternary components of C2 hydrocarbons make the separation of C2H2/C2H6/C2H4 mixtures one of the most challenging tasks in the petrochemical industry. In this study, a family of saturated coordination titanium-based metal–organic frameworks with high stability is constructed for one-step C2H4 purification. Single component adsorption measurements along with dynamic breakthrough experiments illustrated that these MOFs clearly exhibited large adsorption for C2H2 and C2H6 compared to C2H4, and could efficiently extract low concentrations of C2H6 and C2H2 from ternary C2H2/C2H6/C2H4 mixtures simultaneously. Grand canonical Monte Carlo simulations revealed the stronger affinity of the MOFs toward C2H6 and C2H2 compared to C2H4. Furthermore, the mostly intact structure of these MOFs after various examinations revealed their distinctive stability. The reasonably high C2H6 and C2H2 adsorption capacity, ultrahigh structural stability, and excellent separation performance rendered these materials good candidates for C2H4 purification from C2H2/C2H6/C2H4 mixtures in industry.

The removal of low concentration N2 is of great significance and challenging in the industrial production of high-purity O2 . Herein, a chromium-based metal-organic framework, namely, TYUT-96Cr, is reported, which has an unprecedented N2 capture capacity of 37.46 cm3 cm-3 and N2 /O2 (5:95, v/v) selectivity up to 26.95 (298 K and 1 bar), thus setting new benchmarks for all reported metal-organic frameworks and commercially used ones (Li-LSX and 13X). Breakthrough experiments reveal that N2 can be directly extracted from various N2 /O2 (79:21, 50:50, 5:95, and 1:99, v/v) mixtures by this material, affording a record-high O2 -production scale with 99.99% purity. Density functional theory calculations and in situ infrared spectroscopy studies demonstrate that the high-density open Cr (III) sites in TYUT-96Cr can behave as effective Lewis acidic sites, thus resulting in a strong affinity toward N2 . The high N2 adsorption selectivity, exceptional separation performance, and ultrahigh structural stability render this porous material with great potential for this important industrial application.

Ammonia is a hazardous gas and the only carbon-free chemical energy carrier that can be largely adsorbed on metal–organic frameworks (MOFs). However, because of the destructive effect of H2O/NH3 on the metal nodes, most MOFs cannot be applied in ammonia capture and uptake. Herein, three Co-4,5-imidazoledicarboxylic series metal–organic squares (MOSs)—Co4(IDC)4(pda)4, Co4(IDC)4(phen)4, and Co4(IDC)4(bpy)4—were synthesized with a special independent square configuration and zeolite-like supramolecular structures, and their structure and H2O/NH3 uptake capacity were investigated. Based on the four antennas-protected squares and porous structures, the three MOSs have excellent H2O/NH3 stability, whose structures were not affected by the ad-desorption of H2O, NH3, or H2O/NH3. The three MOFs have a H2O uptake of 17.63, 8.35, and 7.75 mmol/g, respectively, as well as the facile release and repeatable of high ammonia uptakes of 11.5, 5.2, and 3.8 mmol/g, respectively. In addition, the MOFs have good stability and...

Synthesis of ultra-high silica (SiO 2 /Al 2 O 3 > 1800) MFI type zeolite such as silicalite-1 is still considered to be luxury because of the long synthesis time (5–12 days). Here, this material with a highly uniform mesoporous (20 nm) structure was crystallized in a shorter time (20 h) using a crystal-seeds method when an appropriate amount of potassium fluoride was added. Characterization techniques including XRD, SEM, TEM and liquid nitrogen adsorption provided detailed information on the two kinds of porous structure silicalite-1. Due to the “smooth” adsorption surface of silicalite-1 containing few equilibrium ions, it is ideal for the separation of gas mixtures containing non-polar molecules with similar physical properties. Moreover, the CH 4 , N 2 , CO 2 and C 2 H 6 adsorption properties were also investigated. Microporous silicalite-1 has a high adsorption capacity for CH 4 , N 2 , CO 2 and C 2 H 6 and adsorption selectivity for CH 4 /N 2 , CO 2 /N 2 , CO 2 /CH 4 and C 2 H 6 /CH 4 . Although a lower adsorption capacity was observed for mesoporous silicalite-1, the pore size did not affect the outstanding adsorption selectivity, on the contrary, the selectivity of mesoporous silicalite-1 was improved.

Solvent-evaporated conversion (SEC) and steam-assisted conversion (SAC) have been developed to prepare the typical metal-organic frameworks (MOFs) Cu-BTC (HKUST-1) and ZIF-8 using a unique solvent recovery strategy using zeolite. As a green circulation medium, zeolite Na-4A loading and removal of solvent (H2O and EtOH) can transport solvent in the vapor phase and avoid solvent condensation, which was the defect in previous SAC syntheses of MOFs, and achieves efficient solvent recovery as well as being an economical and green synthetic process. Moreover, SEC and SAC processes exhibited different mechanisms during the multi-stage reaction and solid diffusion reaction, respectively and both can synthesize the desired products in 12 h. These two methods for MOFs preparation were characterized in detail using XRD, SEM and N2 adsorption during the different growing stages. According to polar molecules (H2O and EtOH) steam-assisted in those synthesis, polar destruction molecules (H2O, NH3) adsorption and stability of Cu-BTC and ZIF-8 was investigated.

The instability of most prototype metal–organic frameworks (MOFs) in the presence of water has limited their industrial scale development. The sensitivity of certain MOFs to humid conditions has been vigorously studied and most of the carrier gas used to make the humid conditions is inert gas. However, a large amount of industrial activities are carried out in air containing 21% oxygen, so it is important to study the effect of oxygen on the hydrostability of MOFs for future industrial applications. In this work, we have studied the stability of M3(BTC)2 (M = Cu, Cr; BTC = 1,3,5-benzenetricarboxylate) under controlled environments (pure oxygen environment; water vapor environment and mixed O2 and H2O environment). The stability was evaluated using water vapor and oxygen adsorption isotherms combined with powder X-ray diffraction (PXRD) experiments and surface area analysis. Our research shows that Cr3(BTC)2 has a relatively high stability under a single atmosphere of either oxygen or water vapor (with Ar). Interestingly, when it was placed under the mixed O2 and H2O environment, it rapidly lost approximately 96% of its original surface area. Cu3(BTC)2 is more stable; however, it was also degraded, especially under a mixed O2 and H2O environment. The experiments show that water molecules and oxygen molecules have a synergistic effect on the stability of MOFs. Computational simulations were used to provide insight into the mechanism governing these trends in the stability of the materials studied.

The development of ethane (C2H6)-selective adsorbents displaying high uptake and selectivity to purify ethylene (C2H4) to obtain polymer-grade raw materials is a meaningful, but challenging process. Tailoring the pore chemistry of a metal-organic framework is an effective strategy used to construct high performance adsorbents. Herein, BUT-10 with a tailored pore environment for tuning the C2H6 adsorption ability has been synthesized via introducing functional sites into UiO-67. The single component gas adsorption capacity, adsorption heat and adsorption selectivity of BUT-10 have been proven to be effectively increased after modifying the pore environment. Computational studies have revealed that the stronger adsorption affinity for C2H6 was achieved via multiple adsorbate-framework interactions in the appropriate pore environment. Breakthrough experiments using BUT-10 as a C2H6-selective adsorbent have shown that polymer grade C2H4 was directly produced from C2H6/C2H4 (1/15 v/v) mixtures using a single separation process under ambient conditions.

The potential of metal–organic frameworks (MOFs) for application in gas separation processes has been widely recognized. Nonetheless, due to their structural instability and high cost, few MOFs have been utilized in the industry. Among them, UiO-66 is one of the most promising materials which displays good structural stability and its preparation is considered economical. Notably, it also provides a valuable platform for the construction of other robust MOFs for various applications. Herein, trifluoromethyl ligands were introduced into the UiO-66 framework to optimize pore environment also to improve its C2H2 recognition ability. Single component adsorption and the corresponding IAST calculation confirmed that compared to UiO-66, UiO-66-(CF3)2 exhibited 2 ~ 3 times higher selectivity for C2H2/C2H4 and C2H2/CO2 separation. Enhanced selectivity resulted in a significantly improved C2H4 separation productivity (56 compared to 36 cm3/cm3) and a reduction in the co-adsorption time. Importantly, the modified UiO-66 framework could be prepared using a simple method and inherited a highly stable structure and good cycling performance of the original material.

Ligand protected noble metal nanoclusters have unique physical and chemical properties and the effects of metal nanoclusters on photoluminescence and energy transfer process for fluorescence molecules are still unclear. In this work, we prepared silver nanoclusters (Ag NCs) with different emission wavelengths (blue, green and red emission) and investigated the energy transfer process between Ag NCs and fluorescein isothiocyanate (FITC). The photoluminescence of FITC can be regulated by the Ag NCs due to various electrons transfer and energy transfer processes between Ag NCs and FITC. The FITC can serve as electrons donor or acceptor which determines the electrons transfer direction between FITC and Ag NCs with different emissions. Astonishingly, the photobleaching of FITC can be effectively inhibited after interacting with Ag NCs, which will surely be of profound significance to the application of FITC.

The performance of a zeolite is often related to its crystal morphology. In this work, the relationship between the crystal morphology of zeolite L and its gas separation performance was evaluated. Cylindrical-L (C-L: 3 × 2 μm), disk-shaped-L (D-L: 0.2 × 1.2 μm), and nanosized-L (N-L: 40 × 25 nm) were synthesized. Various characterization methods, including X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and N2 adsorption–desorption isotherms at 77 K (BET), were employed to obtain complementary information. Due to its small crystal size, the BET specific surface area (427.2 m2/g) and total pore volume (0.382 cm3/g) of N-L are significantly higher than those of D-L (339.6 m2/g and 0.116 cm3/g) and C-L (279.8 m2/g and 0.098 cm3/g). The CO2 adsorption capacity on N-L (70.7 cm3/g) increases 20.9% than that on C-L (58.5 cm3/g). The shorter channel paths in N-L permit faster diffusion and mass transfer than in C-L or D-L, as confirmed by kinetic experiments. Furthermore, breakthrough experiments indicate that N-L has great application potential for separating and capturing CO2 from power-plant flue gas, biogas, or landfill gas.

Down-sizing zeolite crystals to achieve enhanced gas adsorption and separation performances is largely unexplored and underestimated. Nano-sized zeolite can expose more adsorption sites and shorten the diffusion path compared to micro-sized counterparts; however, the synthesis of Nano-sized zeolite is still very challenging. Herein, nano-sized ZK-5 is successfully prepared for the first time via the regulation effects of β-cyclodextrin. The crystal size of ZK-5 can be reduced from micron-size (3 μm) to nano-size (50–100 nm), thus the nano-ZK-5 exhibits a superior surface area (370 cm2 g−1) and pore volume (0.22 cm3 g−1) than the micron-sized sample (149 cm2 g−1 and 0.07 cm3 g−1), which may be due to the reduction in crystal size, which in turn leads to more micropores being detected. The CH4 adsorption capacity on nano-sized sample increased by 64% compared to that of micron-sized ZK-5. Notably, the record-high CH4 adsorption capacity of 1.34 mmol g−1 at 298 K is obtained on the nano-ZK-5 among the commercial zeolites. The equilibrium adsorption selectivity of CH4/N2 (20/80, v/v) mixed gas is as high as 4.2 (IAST method) at 1 bar and 298 K. The adsorption kinetics experiments have illustrated the boosted gas diffusion and mass transfer rate. Furthermore, the breakthrough experiments have confirmed the practical feasibility of separating various gas-mixtures, such as CH4/N2 (20/80, v/v).

Ethylene and acetylene are both important starting materials for the production of polyethylene, vinyl chloride, but-2-yne-1,4-diol, etc. To remove trace acetylene effectively from ethylene and the separation of acetylene from carbon dioxide are particularly challenging in the petrochemical industry. Although catalytic hydrogenation or cryogenic distillation for the separation of such light hydrocarbons is a very mature operation in the current petrochemical industry, it still requires huge capital and energy consumptions. Herein, a metal-organic framework (MOF), [Ni2(BTEC)(bipy)3] (H4BTEC = 1,2,4,5-benzene tetracarboxylic acid, bipy = 4,4′-bipyridine), has been developed for efficient adsorptive separation of C2H2 from C2H2/C2H4 or C2H2/CO2 mixtures. Ni2(BTEC)(bipy)3 exhibited extraordinary two-step adsorption for C2H2 with the adsorption capacity of 76.8 cm3/g at 298 K and 1 bar, significantly discriminating from C2H4 (7.9 cm3/g) and CO2 (13.0 cm3/g) in the same condition. The huge adsorption difference of Ni2(BTEC)(bipy)3 between C2H2 and C2H4/CO2 resulted in the record high uptake ratio for C2H2/C2H4 (9.7), C2H2/CO2 (5.9) and very high ideal adsorption solution selectivity (104, 33.5) in robust MOFs at 298 K and 1 atm. The excellent separation performance was verified by breakthrough experiments; this material could effectively separate C2H2/C2H4 or C2H2/CO2 mixtures directly to obtain high purity of C2H4 (>99.999%) and CO2 (>99.99%) in one separation cycle. Furthermore, this material could be easily scaled up to be synthesized at room temperature under mild conditions, indicating the great potential in actual industrial applications.

The separation of propane (C3H8) from propylene (C3H6) to obtain high purity C3H6 as a petrochemical raw material is an important, but challenging process. In the traditional industrial process, the separation mainly relies on energy-intensive cryogenic distillation. One alternative process that is currently becoming more attractive in the separation of C3H6 is adsorptive separation technology. Using porous materials, especially C3H8 selective adsorbents, high purity C3H6 can be directly obtained and thus, significantly simplifies the process. Herein, a series of functionalized ligands were introduced into UiO-type materials to finely regulate the C3H8 separation performance. Single-component adsorption isotherms reveal that BUT-10 has a distinct binding affinity for C3H8 over C3H6 over a wide range of temperature from 298 to 338 K and thus, achieved by far the highest C3H8 capture capacity (105 cm3 g−1 at 0.1 bar and 298 K) reported among the C3H8-selective materials reported to date. A combination of Grand Canonical Monte Carlo and density-function theory simulations demonstrate that the favorable pore environment provided by the multiple host-guest interactions toward C3H8 result in the higher C3H8 binding affinity observed in the separation process. Breakthrough experiments indicate that BUT-10 can selectively separate C3H8 from C3H8/C3H6 (1/1 and 1/15, v/v) mixtures and thus, directly produces high purity C3H6 (>99.99%) under ambient conditions.