Covalent organic framework (COF) membranes used for selective removal of CO2 were believed as an efficient and low-cost solution to energy and environmental sustainability. In this study, the amide modified COF nanosheet cluster with a 2D structure was facilely prepared through solid reaction, exhibiting good adsorption-based CO2 selectivity (223 at 273 K and 90 at 298 K) toward N2. Remarkably, the mixed matrix membrane (MMM) that consists of a lesser amount of COF filler (1 wt %) shows promising CO2/N2 gas selectivity (∼64). In addition, the competitive adsorption prompts the selectivity to ∼72 under an equimolar CO2/N2 mixture, which surpasses the values of all reported COF membranes. It is worth to note that the binary gas separation is stable during 120 h.Keywords: CO2/N2 gas separation; covalent organic framework; mixed matrix membrane; morphology transformation; solid reaction;

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.

•Factors of governing water resistance of porous coordination polymers were surveyed and discussed.•Representative studies were given with emphasis on adsorptive-based gas separations by water resistant porous coordination polymers.Representative studies were given with emphasis on membrane-based gas separations by water resistant porous coordination polymers.Porous coordination polymer (PCP) chemistry has a promising future because of the tunable structures and excellent properties of polymers. However, the strategy for designing and preparing water-resistant PCPs is a considerable challenge. This review surveys and investigates the factors governing water resistance in a hierarchy sequence. Subsequently, representative studies are provided with an emphasis on their adsorptive- and membrane-based gas separations. This review is intended to be useful for researchers who are interested in designing water-resistant PCPs and exploring promising applications for gas separation.

A new zeolitic-like microporous coordination polymer (PCP), [Zn2(L)·2H2O]·guest (named NTU-17), with crb (BCT) topology was designed and prepared. Interestingly and unusually, it is the first time that such rod-shaped NTU-17 crystals could be converted to morphology-preserved carbon rods with exclusive micropores and a large surface area by using a facile method of direct thermal transformation. Gas adsorption and selectivity showed that these PCP dependent carbon rods are suitable solid adsorbents 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.

A pair of enantiopure chiral porous coordination polymers (PCPs) with a rare utk topology were prepared using derivatives of L-/D-alanine and Zn(CH3COO)2·2H2O. The framework integrated two types of parallel and uniform 1D channels that were constructed by self-stranding of three equal helical chains and a single helical chain. Among them, the right-handed PCP D-NTU-18 showed enhanced enantioseparation towards racemic 1-phenyl-1-propanol.

A new way of pore space partition via secondary metal ions entrapped by pyrimidine hooks is implemented on flexible metal–organic frameworks. The new resulting (3, 4, 6)-connected MOF, HHU-2 (HHU for Hohai University), whose pore space was partitioned by additional metal ions and flexibility was confined under specific pressure and temperature, exhibits promising CO2 uptake capacity (17.5 wt% at 1 bar and 298 K), strong CO2 adsorption enthalpy (30.0 kJ mmol−1), and high CO2 selectivity towards N2 (47.3 at 298 K). Importantly, this is the first example of simultaneously achieving high CO2 selectivity as well as high CO2 uptake capacity in MOFs by flexibility confinement through the introduction of secondary metal sites.

As one kind of important p-type semiconductors, Cr2O3 has been widely used for optical and electronic devices due to its high electrical conductivity and special optoelectronic characteristics, as well as high chemical and thermal stability. In this paper, single-crystalline Cr2O3 nanoplates embedded in carbon matrix were successfully synthesized through direct thermal decomposition of a trinuclear cluster complex of [Cr3O(CH3CO2)6(H2O)3]NO3·CH3COOH ([Cr3O]) in Ar atmosphere. The synergetic effect of the plate-like structure and embedding in carbon matrix contributes to the enhanced electrochemical performance of the Cr2O3-C nanoplates. Owing to different crystallinity and composition, the obtained products at 400, 500, 600, and 700 °C with different carbon content of 12.52, 8.26, 5.35 and 3.27% exhibited enhanced battery-type electrode materials in three-electrode system with high specific capacitance (823.11, 781.65, 720.72, and 696.73 F g−1 at 1 A g−1) and remarkable cycling stability (about 0.3, 2.7, 4.5 and 5.6% loss of its initial capacitance after 5000 charge-discharge cycles at a current density of 5 A g−1). Furthermore, an assembled asymmetric device (Cr2O3-C nanoplates (positive electrode)//activated carbon (AC, negative one)) with an extended operating voltage window of 1.8 V achieves a specific capacitance of 58.06 F g−1 at the current density of 1 A g−1 and an energy density of 26.125 W h kg−1 at power density of 0.9 kW kg−1, as well as superior cycling stability with 91.4% capacitance retention after 10,000 cycles. The results indicate that the Cr2O3 nanoplates embedded in carbon matrix show promising potential to construct high-performance energy storage devices.Single-crystalline Cr2O3 nanoplates embedded in carbon matrix with different crystallinity have been synthesized by calcination of a trinuclear complex of [Cr3O(CH3CO2)6(H2O)3]NO3·CH3COOH in Ar atmosphere. The assembled asymmetric device (Cr2O3-C nanoplates//AC) with an extended operating voltage window of 1.8 V can produce the highest energy density of 26.125 W h kg−1 at power density of 0.9 kW kg−1.Download high-res image (107KB)Download full-size image

From the viewpoint of mathematics and topology, we proposed a rational design and stabilized the first five-fold interpenetrated porous coordination polymer (PCP) with a pcu topology and extra-framework volume (60.0%) by employing a linear ligand with the length of ∼2 nm. The resulting compound exhibits good CO2 uptake, enabling highly selective separation of CO2 from CO2/CO mixtures.

A new methyl-embedded (3,36)-connected txt-type metal–organic framework, {Cu2(DCPEMP)·H2O}n (NJFU-4, H4DCPEMP = 3,5-bis(3,5-dicarboxylphenylethynyl)-4-methylpyridine), was solvothermally synthesized and structurally characterized, which exhibits a BET surface area of 2160 m2 g−1, high stability and high H2 uptake capacity (2.61 wt% at 1 bar and 77 K).

We design and prepare a family of luminescent porous coordination polymers (PCPs) constructed from three C2v symmetry ligands with increased conjugation moieties. Single crystal X-ray analyses revealed that their pore types/sizes and volumes were systematically tuned. Eu-based NTU-5 and NTU-8 emit red light. However, in contrast to the typical green emission of Tb-based PCPs, the increased conjugation moieties in NTU-6 and NTU-9 with a Tb center resulted in a very unusual blue emission. These unique emissions from these iso-structures demonstrated varied pathways of electronic transfer, which were further confirmed by lifetime experiments. Encouraged by these observations, the chromaticity modulation from pink to blue has been well realized by a facile method of self-assembly of the Te-H3L ligand and varied molar ratios of Eu3+/Tb3+ ions. Additionally, NTU-6 and NTU-9 showed high potential for nitrobenzene sensing (quenching effect coefficients: 589.5 and 445.6 M−1) and encapsulation of I2 molecules.

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(L2)2(BDC)0.5]{(CH3)2NH2} decreased a little less than that of IIc [Zn4O(L2)2(2,6-NDC)0.5]{(CH3)2NH2}; however, its selectivity of CO2 toward CH4 increased by almost two times.

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.

A series of new luminescent porous coordination polymers (PCPs) with acylamide groups have been prepared. Single-crystal X-ray analyses revealed that they have isomorphous structures and display significant 1D quadrilateral channels. The luminescence properties of NTU-2 and NTU-3 in the solid state have been studied in detail, which demonstrated that both of them are ideal luminescent sensors for selectively probing Cu2+ ions with high quenching effect coefficients (211.2 and 212.8 M−1). Meanwhile, NTU-2, NTU-3 and NTU-4 show rapid and reversible I2 accommodation properties.

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.

•A new porous structure (La-BTC), and other three previously reported La-based PCPs, were synthesized and characterized.•We firstly and systemically investigated the roles organic units for preparing stable PCPs with carboxylate ligands.•The rod-packed organic units with short distance of adjacent ligands, bridged by metals chains, can access the stable PCP.Despite tremendous efforts, designing and preparing water, chemical, and moisture stable porous coordination polymers (PCPs) with carboxylate ligands remain a challenge. Here, we firstly and systemically investigated the roles of rod-packed organic units for preparing the stable PCPs with different carboxylate ligands. The experimental results demonstrated that the rod packed organic units with short distance of adjacent ligands, bridged by La3 + metal chain, can form water, chemical, and moisture stable PCPs.We firstly and systemically investigate the stability of four La-based PCPs with carboxylate ligands, and demonstrate a new method via bridging of La3 + metal chain by rod packed organic units for accessing stable PCPs.

A new zeolitic-like microporous coordination polymer (PCP), [Zn2(L)·2H2O]·guest (named NTU-17), with crb (BCT) topology was designed and prepared. Interestingly and unusually, it is the first time that such rod-shaped NTU-17 crystals could be converted to morphology-preserved carbon rods with exclusive micropores and a large surface area by using a facile method of direct thermal transformation. Gas adsorption and selectivity showed that these PCP dependent carbon rods are suitable solid adsorbents for CH4 purification.

A new, highly porous acylamide-functionalized MOF with a (3,24)-connected rht-type network (HNUST-5) has been synthesized and structurally determined using powder X-ray diffraction. HNUST-5 exhibits a high BET surface area of 3643 m2 g−1, and a large CO2 uptake capability (38.9 mmol g−1 under 36 bar) with an excellent selectivity of CO2/CH4 (7.3) and CO2/N2 (32.5) at 273 K.