ABSTRACT
Nuclear energy is a competitive and environmentally friendly low-carbon energy source. It is seen as an important avenue for satisfying energy demands, responding to the energy crisis, and mitigating global climate change. However, much attention has been paid to achieving the effective treatment of radionuclide ions produced in nuclear waste. Initially, advanced adsorbents were mainly available in powder form, which meant that additional purification processes were usually required for separation and recovery in industrial applications. Therefore, to meet the practical requirements of industrial applications, materials need to be molded and processed into forms such as beads, membranes, gels, and resins. Here, we summarize the fabrication of porous materials used for capturing typical radionuclide ions, including UO2 2+, TcO4 -, IO3 -, SeO3 2-, and SeO4 2-.
ABSTRACT
Nuclear industry spent fuel reprocessing and some radioactive contamination sites often involve high acidity and salinity environments. Currently developed and reported sorbents in 99 TcO4 - sequestration from the nuclear waste are unstable and show low adsorption efficiency in harsh conditions. To address this issue, we developed a post-synthetic modification strategy by grafting imidazole-based ionic liquids (ILs) onto the backbone of covalent organic framework (COF) via vinyl polymerization. The resultant COF-polyILs sorbent exhibits fast adsorption kinetics (<5â min) and good sorption capacity (388â mg g-1 ) for ReO4 - (a nonradioactive surrogate of 99 TcO4 - ). Outstandingly, COF-polyILs composite shows superior ReO4 - removal even under highly acidic conditions and in the presence of excess competing ions of Hanford low-level radioactive waste stream, benefiting from the stable covalent bonds between the COF and polyILs, mass of imidazole rings, and hydrophobic pores in COF.
ABSTRACT
Considering the importance of C2H2 in industry, it is of great significance to develop porous materials for efficient C2H2/CO2 separation. Besides the high selectivity, the C2H2 adsorption capacity is another vital factor in C2H2/CO2 separation. However, the "trade-off" between these two factors is still perplexing. Rational pore design of metal-organic frameworks (MOFs) has been proven to be an effective way to solve the above problem. In this work, we have appropriately combined three kinds of strategies in the design of the MOF (FJI-H33), i.e., the introduction of open metal sites, construction of cage-like cavities, and adjustment of moderate pore size. As anticipated, FJI-H33 exhibits both outstanding C2H2 adsorption capacity and high C2H2/CO2 selectivity. At 298 K and 100 kPa, the C2H2 storage capacity of FJI-H33 is 154 cm3/g, while the CO2 uptake is only 80 cm3/g. The ideal adsorbed solution theory (IAST) selectivity of C2H2/CO2 (50:50) is calculated as high as 15.5 at 298 K. More importantly, the excellent practical separation performance was verified by breakthrough experiments. In addition, the calculation of adsorption sites and relevant energy by density functional theory (DFT) provides a good explanation for the excellent separation performance and pore design strategy.
ABSTRACT
Porous supramolecular assemblies constructed by noncovalent interactions are promising for adsorptive purification of methane because of their easy regeneration. However, the poor stability arising from the weak noncovalent interactions has obstructed their practical applications. Here, we report a robust and easily regenerated polyhedron-based cationic framework assembled from a metal-organic square. This material exhibits a very low affinity for CH4 and N2 , but captures other competing gases (e.g. C2 H6 , C3 H8 , and CO2 ) with a moderate affinity. These results underpin highly selective separation of a range of gas mixtures that are relevant to natural gas and industrial off-gas. Dynamic breakthrough studies demonstrate its practical separation for C2 H6 /CH4 , C3 H8 /CH4 , CO2 /N2 , and CO2 /CH4 . Particularly, the separation time is ≈11â min g-1 for the C2 H6 /CH4 (15/85 v/v) mixture and ≈49â min g-1 for the C3 H8 /CH4 (15/85 v/v) mixture (under a flow of 2.0â mL min-1 ), respectively, enabling its capability for CH4 purification from light alkanes.
Subject(s)
Carbon Dioxide , Methane , Adsorption , Porosity , Metals , GasesABSTRACT
Because C2 H4 plays an essential role in the chemical industry, economical and energy-efficient separation of ethylene (C2 H4 ) from ethane (C2 H6 ) is extremely important. With the exception of energy-intensive cryogenic distillation, there are few one-step methods to obtain polymer-grade (≥99.95 % pure) C2 H4 from C2 H4 /C2 H6 mixtures. Here we report a highly stable metal-organic-framework (MOF) FJI-H11-Me(des) (FJI-H=Hong's group in Fujian Institute of Research on the Structure of Matter) which features one-dimensional hexagonal nonpolar pore surfaces constructed by aromatic rings and alkyl groups. This FJI-H11-Me(des) adsorbs C2 H6 rather than C2 H4 between 273 and 303â K. Practical breakthrough experiments with C2 H4 containing 1 % C2 H6 have shown that FJI-H11-Me(des) can realize the acquisition in one-step of polymer-grade, 99.95 % pure C2 H4 under various conditions including different gas flow rates, temperatures and relative humidity.
ABSTRACT
The separation of C2-C3 alkyne/alkene mixtures is important but difficult work thanks to their similar physical and chemical properties. Crystalline porous materials with high alkyne adsorption and prominent separation selectivity of alkyne/alkene mixtures have been extensively investigated because of their energy-saving merits. Herein, we report a fluorinated hybrid microporous material (FJI-W1) that exhibits unexpected water and thermal stability. Gas sorption isotherms show that FJI-W1 has ultrahigh C2H2 and C3H4 adsorption capacities of 150 and 159 cm3/g, respectively. Furthermore, dynamic breakthrough experiments indicate that the intervals of breakthrough time between the two gases for 1:99 (v/v) C2H2/C2H4 and 1:99 (v/v) C3H4/C3H6 can be up to 230 and 600 min/g, respectively. Additionally, the tests with different flow rates and three-cycle breakthrough tests demonstrate that FJI-W1 has a remarkable C2-C3 alkyne/alkene separation performance.
ABSTRACT
Adsorption-based separation is an important technology for C2 H2 purification due to the environmentally friendly and energy-efficient advantage. In addition to the high selectivity of C2 H2 /CO2 , the high uptake of C2 H2 also plays an important role in the separation progress. However, the trade-off between adsorption capacity and separation performance is still in a dilemma. Herein, we report a series of cage-like porous materials named FJI-H8-R (R=Me, Et, n Pr and i Pr) which all have high C2 H2 uptakes at 1â bar and 298â K. Dynamic breakthrough studies show that they all exhibit excellent C2 H2 /CO2 separation performance. Particularly, FJI-H8-Me possesses a long breakthrough time up to 90â min g-1 . Additionally, Grand Canonical Monte Carlo (GCMC) simulation reveals that the suitable pore space and geometry contribute much to the excellent separation performance.
ABSTRACT
Despite much intense investigation on the C2 H2 /CO2 separation, the trade-off between the adsorption capacity and separation selectivity is still tricky. To overcome the dilemma, we have rationally synthesized an ultra-stable fluorinated hybrid porous material SIFSIX-Cu-TPA with the ith-d topology. Completely differing from the famous pillar-layer fluorinated materials, SIFSIX-Cu-TPA possesses a unique pillar-cage structure, in which the SiF6 2- anions cross-link two adjacent metal nodes as pillars to stabilize the three-dimensional framework constructed by icosahedral and tetrahedral cages. As anticipated, SIFSIX-Cu-TPA has high BET surface area (1330â m2 g-1 ) as well as high C2 H2 uptake (185â cm3 g-1 at 298â K and 1â bar). At the same time, due to the obvious difference in the adsorption performance of CO2 and C2 H2 especially in the low pressure area, SIFSIX-Cu-TPA also exhibits an excellent C2 H2 /CO2 separation performance (breakthrough time up to 68â min g-1 at 298â K and 1â bar).
ABSTRACT
Fluorescent agents play an important role in the peroxyoxalate chemiluminescence system. However, the effect of different frameworks on chemiluminescence (CL) has not been explored. Herein two pyrene-based metal-organic frameworks (MOFs), [Pb2L]n·2nDMA·2nH2O (1) and [(Ca2L)·(DMF)3]n·2.5nDMF·6nH2O (2) (H4L = 5,5'-(-pyrene-1,6-diyl)-diisophthalic acid; DMA = N,N'-dimethylacetamide; DMF = N,N'-dimethylformamide), have been successfully synthesized and are applied to CL. They both exhibit strong and lasting emission that is visible to the naked eye and is significantly stronger than that of the ligand. More importantly, compared with 2, 1 has notably better CL performance. We infer that the reason may be that 1 has higher stability and larger open channels, which can avoid the aggregation of organic ligands as well as provide an effective pathway for the active substance to diffuse into the channels.
ABSTRACT
The pore engineering of microporous metal-organic frameworks (MOFs) has been extensively investigated in the past two decades, and an expansive library of functional groups has been introduced into various frameworks. However, the reliable procurement of MOFs possessing both a targeted pore size and preferred functionality together is less common. This is especially important since the applicability of many elaborately designed materials is often restricted by the small pore sizes of microporous frameworks. Herein, we designed and synthesized a mesoporous MOF based on Zr6 clusters and tetratopic carboxylate ligands, termed PCN-808. The accessible coordinatively unsaturated metal sites as well as the intrinsic flexibility of the framework make PCN-808 a prime scaffold for postsynthetic modification via linker installation. A linear ruthenium-based metalloligand was successfully and precisely installed into the walls of open channels in PCN-808 while maintaining the mesoporosity of the framework. The photocatalytic activity of the obtained material, PCN-808-BDBR, was examined in the aza-Henry reaction and demonstrated high conversion yields after six catalytic cycles. Furthermore, thanks to the mesoporous nature of the framework, PCN-808-BDBR also exhibits exceptional yields for the photocatalytic oxidation of dihydroartemisinic acid to artemisinin.
ABSTRACT
For the first time, a new square Ca4O SBU is introduced into a 3D Ca-MOF, ([MeNH2]2[Ca4O(MTB)2(EtOH)4])·(solvent)n (1), to generate a (4,8)-connected flu-topology structure. Compound 1 exhibits selective adsorption of C3 and C2 hydrocarbons and CO2 over CH4 with especially high IAST selectivities for C3 hydrocarbons over CH4 (at 15/85 and 50/50 ratio) at 298K and 1 bar.
ABSTRACT
A robust microporous material (FJI-H19), which is constructed from distorted cuboctahedral cages and distorted octahedral cages, has been successfully synthesized. FJI-H19 possesses good thermal and water stability as well as highly selective adsorption of C3 and C4 hydrocarbons over CH4 under ambient conditions. More importantly, the high selectivities for the separation of CH4/C3 or C4 mixtures (85/15) have not only been estimated by ideal adsorbed solution theory (IAST) but also definitely confirmed by breakthrough experiments.