One-Step Synthesis of Polyethyleneimine-Grafted Styrene-Maleic Anhydride Copolymer Adsorbents for Effective Adsorption of Anionic Dyes.

Wastewater containing organic dyes has become one of the important challenges in water treatment due to its high salt content and resistance to natural degradation. In this work, a novelty adsorbent, PEI-SMA, was prepared by grafting polyethyleneimine (PEI) onto styrene-maleic anhydride copolymer (SMA) through an amidation reaction. The various factors, such as pH, adsorbent dosage, contact time, dye concentration, and temperature, which may affect the adsorption of PEI-SMA for Reactive Black 5 (RB5), were systematically investigated by static adsorption experiments. The adsorption process of PEI-SMA for RB5 was more consistent with the Langmuir isotherm model and the pseudo-second-order model, suggesting a single-layer chemisorption. PEI-SMA exhibits excellent adsorption performance for RB5 dye, with a maximum adsorption capacity of 1749.19 mg g-1 at pH = 2. Additionally, PEI-SMA exhibited highly efficient RB5 competitive adsorption against coexisting Cl- and SO42- ions and cationic dyes. The adsorption mechanism was explored, and it can be explained as the synergistic effect of electrostatic interaction, hydrogen bonding and π-π interaction. This study demonstrates that PEI-SMA could act as a high performance and promising candidate for the effective adsorption of anionic dyes from aqueous solutions.

A Metal-Organic Framework with Nonpolar Pore Surfaces for the One-Step Acquisition of C2 H4 from a C2 H4 and C2 H6 Mixture.

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 303 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.

Cage-Like Porous Materials with Simultaneous High C2 H2 Storage and Excellent C2 H2 /CO2 Separation Performance.

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 1 bar and 298 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 90 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.

Building a robust 3D Ca-MOF by a new square Ca4O SBU for purification of natural gas.

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.

A robust cage-based framework for the highly selective purification of natural gas.

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.

A Multifunctional Nanocage-based MOF with Tri- and Tetranuclear Zinc Cluster Secondary Building Units.

A new Zn-cluster based MOF, [Zn21(BTC)11(µ3-OH)3(µ4-O)3(H2O)18]·21EtOH (1) (H3BTC = 1,3,5-benzenetricarboxylic acid), with two different types of cluster nodes has been successfully synthesized from Zn2+ and H3BTC under the solvothermal conditions. Single crystal X-ray diffraction studies reveal that 1 is a 3D trinodal (3,5,6)-c framework which features a large octahedral cage organized by nine Zn3O and nine Zn4O clusters SBUs and twenty-four triangular BTC3- linkers. The Eu3+/Tb3+-incorporated derivative of 1 with 0.251% Eu3+ and 0.269% Tb3+ exhibits tunable luminescence from yellow to white and then to blue-green by changing the excitation wavelength from 308 to 315 nm. Metal ion exchange with Cu2+ affords isomorphous Cu-based MOF with enhanced N2 and CO2 adsorption capacity. In addition, 1 can act as a selective luminescent sensor for Cu2+ and Al3+ ions.

Selective CO2 Capture and High Proton Conductivity of a Functional Star-of-David Catenane Metal-Organic Framework.

Network structures based on Star-of-David catenanes with multiple superior functionalities have been so far elusive, although numerous topologically interesting networks are synthesized. Here, a metal-organic framework featuring fused Star-of-David catenanes is reported. Two triangular metallacycles with opposite handedness are triply intertwined forming a Star-of-David catenane. Each catenane fuses with its six neighbors to generate a porous twofold intercatenated gyroid framework. The compound possesses exceptional stability and exhibits multiple functionalities including highly selective CO2 capture, high proton conductivity, and coexistence of slow magnetic relaxation and long-range ordering.

An Ultrastable and Easily Regenerated Hydrogen-Bonded Organic Molecular Framework with Permanent Porosity.

A robust hydrogen-bonded organic framework HOF-TCBP (H4 TCBP=3,3',5,5'-tetrakis-(4-carboxyphenyl)-1,1'-biphenyl) has been successfully constructed and structurally characterized. It possesses a permanent 3D porous structure with a 5-fold interpenetrated dia topological network. This activated HOF-TCBP has a high BET surface area of 2066 m2 g-1 and is capable of highly selective adsorption and separation of light hydrocarbons under ambient conditions. It shows excellent thermal stability, as demonstrated by PXRD experiments and N2 adsorption tests. Practical use of HOF-TCBP is facilitated by the ease of its preparation and renewal through rotary evaporation.

Visualizing the Dynamics of Temperature- and Solvent-Responsive Soft Crystals.

We demonstrate that three flexible MOFs termed FJI-H11-R (FJI-H=Hong's group in Fujian Institute of Research on the Structure of Matter, R=Me, Et, (i) Pr) can reversibly respond to temperature and solvents via structural transformations, which can be visualized by in situ single-crystal X-ray snapshot analyses. FJI-H11-R exhibit colossal anisotropic thermal expansion, with a record-high uniaxial positive thermal-expansion coefficient of 653.2×10(-6)  K(-1) observed in FJI-H11-Me. Additionally, large c-axial shrinkage of 32.4 % is also observed during desolvation. The stimuli-responsive mechanism reveals the structural evolutions are related to the rotations and deformations of the organic linkers.

Magnetic Properties of 3D Heptanuclear Lanthanide Frameworks Supported by Mixed Ligands.

Two 3D lanthanide frameworks, [Ln7(DPA)5(NA)3(µ3-OH)8(H2O)3]·2.5H2O [H2DPA = diphenic acid; HNA = nicotinic acid; Ln = Gd (1), Dy (2)], were synthesized and structurally characterized. They were rarely seen examples of 3D frameworks constructed from heptanuclear trigonal-antiprismatic lanthanide clusters with mixed H2DPA and HNA ligands. Both 1 and 2 show typical antiferromagnetic interactions. Additionally, complex 1 possesses a large magnetocaloric effect of 34.15 J kg(-1) K(-1).

An independent 1D single-walled metal-organic nanotube transformed from a 2D layer exhibits highly selective and reversible sensing of nitroaromatic compounds.

The syntheses and structures of two new Zn(II) complexes, a 2D graphite-like layer {[Zn(PIA)H2 O]⋅H2 O}n (1) and an independent 1D single-walled metal-organic nanotube (SWMONT) {[Zn2 (PIA)2 (bpy)2 ]⋅2.5 H2 O⋅DMA}n (2), have been reported based on a "Y"-shaped 5-(pyridine-4-yl)isophthalic acid ligand (H2 PIA). Interestingly, the 2D graphite-like layer in 1 can transform into the independent 1D SWMONT in 2 with addition of 2,2'-bipyridine (bpy), which represents the first successfully experimental example of an independent 1D metal-organic nanotube generated from a 2D layer by a "rolling-up" mechanism.