Jingui Duan

High CO2/N2/O2/CO separation in a chemically robust porous coordination polymer with low binding energy

Porous coordination polymers (PCPs), constructed from organic linkers and metal ions, can provide special pore environments for selective CO2 capture. Although many PCPs have been reported, a rational design for identifying PCPs that adsorb CO2 molecules with a low binding energy, high separation ability and high chemical stability remains a great challenge. Here, we propose and validate, experimentally and computationally, a new PCP, [La(BTN)DMF]·guest (PCP-1⊃guest), that has a large aromatic organic surface and a low binding energy for high CO2 separation from four-gas mixtures (CO2–N2–O2–CO) at ambient temperature. In addition, it shows good water and chemical stability; in particular, it is stable from pH = 2 to 12 at 100 °C, which is unprecedented for carboxylate-based PCPs.

Natural Gas Purification Using a Porous Coordination Polymer with Water and Chemical Stability

Porous coordination polymers (PCPs), constructed by bridging the metals or clusters and organic linkers, can provide a functional pore environment for gas storage and separation. But the rational design for identifying PCPs with high efficiency and low energy cost remains a challenge. Here, we demonstrate a new PCP, [(Cu4Cl)(BTBA)8·(CH3)2NH2)·(H2O)12]·xGuest (PCP-33⊃guest), which shows high potential for purification of natural gas, separation of C2H2/CO2 mixtures, and selective removal of C2H2 from C2H2/C2H4 mixtures at ambient temperature. The lower binding energy of the framework toward these light hydrocarbons indicates the reduced net costs for material regeneration, and meanwhile, the good water and chemical stability of it, in particular at pH = 2 and 60 °C, shows high potential usage under some harsh conditions. In addition, the adsorption process and effective site for separation was unravelled by in situ infrared spectroscopy studies.

Design of Superhydrophobic Porous Coordination Polymers through the Introduction of External Surface Corrugation by the Use of an Aromatic Hydrocarbon Building Unit

We demonstrate a new approach to superhydrophobic porous coordination polymers by incorporating an anisotropic crystal morphology featuring a predominant surface that is highly corrugated and terminated by aromatic hydrocarbon moieties. The resulting low-energy surface provides particularly promising hydrophobic properties without the need for postsynthetic modifications or surface processing that would block the porosity of the framework. Consequently, hydrophobic organic molecules and water vapor are able to penetrate the surface and be densely accommodated within the pores, whereas bulk water is repelled as a result of the exterior surface corrugation derived from the aromatic surface groups. This study provides a new strategy for the design and development of superhydrophobic porous materials.

A Family of Rare Earth Porous Coordination Polymers with Different Flexibility for CO2/C2H4 and CO2/C2H6 Separation

A family of new porous coordination polymers (PCPs) were prepared by the reaction of an acylamide modified ligand (H3L) and RE(NO)3·xH2O (RE = Y, La, Ce, Nd, Eu, Tb, Dy, Ho, and Tm). PXRD and single-crystal X-ray analyses of them revealed that, besides the La PCP, all other rare earth members gave isomorphous structures. The two types of structural toplogies obtained, although similar, differ in their alignment of acylamide functional groups and structural flexibility. Adsorption experiments and in situ DRIFT spectra showed that rigid frameworks have the typical microporous behavior and poor selective capture of CO2 over C2H4 and C2H6; however, the unique La-PCP with structural flexibility and close-packed acylamide groups has a high selective capture of CO2 with respect to C2H6 or C2H4 at 273 K, especially at the ambient pressure area (0.1-1 bar).

Density Gradation of Open Metal Sites in the Mesospace of Porous Coordination Polymers

The prevalence of the condensed phase, interpenetration, and fragility of mesoporous coordination polymers (meso-PCPs) featuring dense open metal sites (OMSs) place strict limitations on their preparation, as revealed by experimental and theoretical reticular chemistry investigations. Herein, we propose a rational design of stabilized high-porosity meso-PCPs, employing a low-symmetry ligand in combination with the shortest linker, formic acid. The resulting dimeric clusters (PCP-31 and PCP-32) exhibit high surface areas, ultrahigh porosities, and high OMS densities (3.76 and 3.29 mmol g-1, respectively), enabling highly selective and effective separation of C2H2 from C2H2/CO2 mixtures at 298 K, as verified by binding energy (BE) and electrostatic potentials (ESP) calculations.

Two solvent-dependent porous coordination polymers with –OH decorated ligands: unusual non-crystallographic net and fsh topology

Two new porous coordination polymers (PCPs), ([Cu6(L)4·(H2O)6]·10DMA·4EtOH, (1) and [Cu5(L)2 (OH)2·(H2O)2·DMA2]·2DMA·EtOH·2H2O (2), were solvothermally synthesized and structurally characterized. Interestingly, their variable architectures controlled by solvent system exhibit a structural progression from an unusual non-crystallographic (NC) net to a (4,6)-connected framework with fsh topology. Moreover, the combination of 3D channels of about 3.0 × 7.2, 4.7 × 9.5, and 6.3 × 7.8 A2, and functional –OH groups in 2′ lead to good selectivity of CO2 over CH4 (26-55 by IAST) at 273 K.

Predesign and Systematic Synthesis of 11 Highly Porous Coordination Polymers with Unprecedented Topology

We propose and validate a simple strategy of vertex connection that can be used for framework design and pore size/type modulation to prepare a mother structure and another 10 highly porous isoreticular frameworks with unprecedented topology. Importantly, the potential accessible pore volumes (57-71%), pore sizes (6.8-11. 2 Å; 17.0-29.0 Å; 12.5-22.8 Å; 11.9-24.5 Å), and the pore shapes of this series of highly porous frameworks were simultaneously and systematically tuned. Interestingly, the pore size of IIa [Zn4O(L(2))2(BDC)0.5]{(CH3)2NH2} decreased a little less than that of IIc [Zn4O(L(2))2(2,6-NDC)0.5]{(CH3)2NH2}; however, its selectivity of CO2 toward CH4 increased by almost two times.

A new mesoporous coordination polymer: synthesis, structure, and gas adsorption studies

A new porous coordination framework, [Cu3(BTN)2(H2O)3]·xGuest (NJTU-1), with a large aromatic organic surface and remarkable mesopores, was synthesized and structurally characterized. It exhibits the second highest BET surface area of 2800 m2 g−1 among the interpenetrated PCPs. Additionally, this PCP also demonstrates high CH4 (excess amount: 174 cm3 g−1), C2H4 (220 cm3 g−1), C2H6 (299 cm3 g−1) and CO2 (298 cm3 g−1) uptake capacities as well as good adsorption selectivities for C2H4 (12–145), C2H6 (15.5–380) and CO2 (7.1–31.6) over CH4 at 298 K.

Fine-tuning optimal porous coordination polymers using functional alkyl groups for CH4 purification

Nano-porous coordination polymers (nano-PCPs), as a new class of crystalline material, have become a lucrative topic in coordination chemistry due to the facile tunability of their functional pore environments. However, elucidating the pathways for the rational design and preparation of nano-PCPs with various integrated properties for feasible gas separation remains a great challenge. Here, we demonstrate a new route to achieve nano-PCPs with an integrated pore system and physical properties using a reticular chemistry strategy. By optimizing the position and length of the shortest two alkyl groups in the channels, unprecedented phenomena of improved surface area, gas uptake, gas selectivity, thermal stability and chemical stability were observed in the PCPs, especially in NTU-14, the structure with a pendant ethyl group. Furthermore, the high performance of adsorption- and membrane-based separation makes NTU-14 a promising medium for CH4 purification from a mixture at room temperature.

Finely Controlled Stepwise Engineering of Pore Environments and Mechanistic Elucidation of Water-Stable, Flexible 2D Porous Coordination Polymers

Two porous coordination polymers (PCPs) with different topologies (NTU-19: sql and NTU-20: dia) underwent finely controlled, stepwise crystal conversions to yield a common water-stable, flexible 2D framework (NTU-22: kgm). The crystal conversions occurred directly at higher temperature via the 3D intermediate (NTU-21: nbo), which could be observed at lower temperature. The successful isolation of the intermediate product of NTU-21, characterization with in situ PXRD and UV/Vis spectra were combined with DFT calculations to allow an understanding of the dynamic processes at the atomic level. Remarkably, breakthrough experiments demonstrate NTU-22 with integral structural properties allowed significant CO2 /CH4 mixture separation.