Pressure- and Heat-Induced Insertion of CO2 into an Auxetic Small-Pore Zeolite

High-Pressure Insertion of Dense H2 into a Model Zeolite

Our combined high-pressure synchrotron X-ray diffraction and Monte Carlo modeling studies show super-filling of the zeolite, and computational results suggest an occupancy by a maximum of nearly two inserted H2 molecules per framework unit, which is about twice that observed in gas hydrates. Super-filling prevents amorphization of the host material up to at least 60 GPa, which is a record pressure for zeolites and also for any group IV element being in full 4-fold coordination, except for carbon. We find that the inserted H2 forms an exotic topologically constrained glassy-like form, otherwise unattainable in pure hydrogen. Raman spectroscopy on confined H2 shows that the microporosity of the zeolite is retained over the entire investigated pressure range (up to 80 GPa) and that intermolecular interactions share common aspects with bulk hydrogen, while they are also affected by the zeolite framework.

Pressure- and Temperature-Induced Insertion of N2, O2 and CH4 to Ag-Natrolite

This paper aimed to investigate the structural and chemical changes of Ag-natrolite (Ag₁₆Al₁₆Si₂₄O₈₀·16H₂O, Ag-NAT) in the presence of different pressure transmitting mediums (PTMs), such as N₂, O₂ and CH₄, up to ~8 GPa and 250 °C using in situ synchrotron X-ray powder diffraction and Rietveld refinement. Pressure-induced insertion occurs in two stages in the case of N₂ and O₂ runs, as opposed to the CH₄ run. First changes of the unit cell volume in N₂, O₂ and CH₄ runs are observed at 0.88(5) GPa, 1.05(5) GPa and 1.84(5) GPa with increase of 5.7(1)%, 5.5(1)% and 5.7(1)%, respectively. Subsequent volume changes of Ag-natrolite in the presence of N₂ and O₂ appear at 2.15(5) GPa and 5.24(5) GPa with a volume increase of 0.8(1)% and a decrease of 3.0(1)%, respectively. The bulk moduli of the Ag-NAT change from 42(1) to 49(7), from 38(1) to 227(1) and from 49(3) to 79(2) in the case of N₂, O₂ and CH₄ runs, respectively, revealing that the Ag-NAT becomes more incompressible after each insertion of PTM molecules. The shape of the channel window of the Ag-NAT changes from elliptical to more circular after the uptake of N₂, O₂ and CH₄. Overall, the experimental results of Ag-NAT from our previous data and this work establish that the onset pressure exponentially increases with the molecular size. The unit cell volumes of the expanded (or contracted) phases of the Ag-NAT have a linear relationship and limit to maximally expand and contract upon pressure-induced insertion.

Elucidation of the Structural Origins and Contrasting Guest-Host Interactions in CO2 -Loaded CdSDB and PbSDB Metal-Organic Frameworks at High Pressures

PbSDB and CdSDB (SDB=4,4'-sulfonyldibenzoate) are two structurally related SDB-based metal-organic frameworks (MOFs) that demonstrate promising potential for selective CO₂ adsorption capabilities. The structural stabilities and guest-host interactions between CO₂ and PbSDB or CdSDB frameworks at high pressures up to 13 GPa in situ were comparatively investigated by Raman spectroscopy, FTIR spectroscopy, and synchrotron X-ray diffraction. Although both empty frameworks exhibited high chemical stabilities upon compression, they show different pressure-induced modifications in crystallinity. This difference can be attributed to their different coordination topologies that result in near isotropic contraction of unit cells for the CdSDB framework but anisotropic for the PbSDB framework. Furthermore, the CO₂ -loaded PbSDB and CdSDB frameworks at high pressures show strongly contrasting guest-host interactions in terms of the pressure-regulated CO₂ adsorption sites. In both frameworks, pressure can highly efficiently promote the formation of new CO₂ adsorption sites and the enhancement of guest-host interactions. In the CO₂ -loaded PbSDB framework, in particular, the peculiar pressure-tuned CO₂ population was observed preferentially on one of the two adsorption sites in response to external compression. These unique guest-host interaction behaviors can also be unambiguously correlated to their different topological origins. These findings for the PbSDB and CdSDB frameworks provide in-depth understanding of the structure-property relationship, which is of fundamental importance for CO₂ storage application in SDB-based MOFs.

Porous Carbon Materials Based on Graphdiyne Basis Units by the Incorporation of the Functional Groups and Li Atoms for Superior CO2 Capture and Sequestration

The graphdiyne family has attracted a high degree of concern because of its intriguing and promising properties. However, graphdiyne materials reported to date represent only a tiny fraction of the possible combinations. In this work, we demonstrate a computational approach to generate a series of conceivable graphdiyne-based frameworks (GDY-Rs and Li@GDY-Rs) by introducing a variety of functional groups (R = -NH₂, -OH, -COOH, and -F) and doping metal (Li) in the molecular building blocks of graphdiyne without restriction of experimental conditions and rapidly screen the best candidates for the application of CO₂ capture and sequestration (CCS). The pore topology and morphology and CO₂ adsorption and separation properties of these frameworks are systematically investigated by combining density functional theory (DFT) and grand canonical Monte Carlo (GCMC) simulations. On the basis of our computer simulations, combining Li-doping and hydroxyl groups strategies offer an unexpected synergistic effect for efficient CO₂ capture with an extremely CO₂ uptake of 4.83 mmol/g at 298 K and 1 bar. Combined with its superior selectivity (13 at 298 K and 1 bar) for CO₂ over CH₄, Li@GDY-OH is verified to be one of the most promising materials for CO₂ capture and separation.

Effects of Sulfur Doping and Humidity on CO2 Capture by Graphite Split Pore: A Theoretical Study

By use of grand canonical Monte Carlo calculations, we study the effects of sulfur doping and humidity on the performance of graphite split pore as an adsorbent for CO₂ capture. It is demonstrated that S doping can greatly enhance pure CO₂ uptake by graphite split pore. For example, S-graphite split pore with 33.12% sulfur shows a 39.85% rise in pure CO₂ uptake (51.001 mmol/mol) compared with pristine graphite split pore at 300 K and 1 bar. More importantly, it is found that S-graphite split pore can still maintain much higher CO₂ uptake than that by pristine graphite split pore in the presence of water. Especially, uptake by 33.12% sulfur-doped S-graphite split pore is 51.963 mmol of CO₂/mol in the presence of water, which is 44.34% higher than that by pristine graphite split pore at 300 K and 1 bar. In addition, CO₂/N₂ selectivity of S-graphite split pore increases with increasing S content, resulting from stronger interactions between CO₂ and S-graphite split pore. Moreover, by use of density functional theory calculations, we demonstrate that S doping can enhance adsorption energy between CO₂ molecules and S-graphene surface at different humidities and furthermore enhance CO₂ uptake by S-graphite split pore. Our results indicate that S-graphite split pore is a promising adsorbent material for humid CO₂ capture.

[Cu3(BTC)2]-polyethyleneimine: an efficient MOF composite for effective CO2separation

Cu-BTC MOF and a series of polyethyleneimine (PEI) incorporated Cu-BTC composites (Cu-BTC–PEI) have been developed for CO₂separation.

Insertion of N2 into the Channels of AFI Zeolite under High Pressure

We present an experimental study of a new hybrid material where nitrogen is encapsulated in the channels of porous zeolite AlPO₄-5 (AFI) single crystals by a high-pressure method. The high-pressure behavior of nitrogen confined inside the AFI nano-channels is then investigated by Raman spectroscopy up to 44 GPa. Under pressure, the Raman modes of confined nitrogen show behaviors different from those of the bulk nitrogen. After the return to atmospheric pressure, it is demonstrated that non-gaseous nitrogen can be effectively stabilized by being confined inside the intact AFI sample. This result provides new insight into nitrogen capture and storage technologies.

Enhanced interfacial interaction and CO2 separation performance of mixed matrix membrane by incorporating polyethylenimine-decorated metal-organic frameworks

Polyethylenimine (PEI) was immobilized by MIL-101(Cr) (∼550 nm) via a facile vacuum-assisted method, and the obtained PEI@MIL-101(Cr) was then incorporated into sulfonated poly(ether ether ketone) (SPEEK) to fabricate mixed matrix membranes (MMMs). High loading and uniform dispersion of PEI in MIL-101(Cr) were achieved as demonstrated by ICP, FT-IR, XPS, and EDS-mapping. The PEI both in the pore channels and on the surface of MIL-101(Cr) improved the filler-polymer interface compatibility due to the electrostatic interaction and hydrogen bond between sulfonic acid group and PEI, and simultaneously rendered abundant amine carriers to facilitate the transport of CO2 through reversible reaction. MMMs were evaluated in terms of gas separation performance, thermal stability, and mechanical property. The as-prepared SPEEK/PEI@MIL-101(Cr) MMMs showed increased gas permeability and selectivity, and the highest ideal selectivities for CO2/CH4 and CO2/N2 were 71.8 and 80.0 (at a CO2 permeability of 2490 Barrer), respectively. Compared with the membranes doped with unfilled MIL-101(Cr), the ideal selectivities of CO2/CH4 and CO2/N2 for PEI@MIL-101(Cr)-doped membranes were increased by 128.1 and 102.4 %, respectively, at 40 wt % filler loading, surpassing the 2008 Robeson upper bound line. Moreover, the mechanical property and thermal stability of SPEEK/PEI@MIL-101(Cr) were enhanced.

Pressure-induced metathesis reaction to sequester Cs

We report here a pressure-driven metathesis reaction where Ag-exchanged natrolite (Ag16Al16Si24O80·16H2O, Ag-NAT) is pressurized in an aqueous CsI solution, resulting in the exchange of Ag(+) by Cs(+) in the natrolite framework forming Cs16Al16Si24O80·16H2O (Cs-NAT-I) and, above 0.5 GPa, its high-pressure polymorph (Cs-NAT-II). During the initial cation exchange, the precipitation of AgI occurs. Additional pressure and heat at 2 GPa and 160 °C transforms Cs-NAT-II to a pollucite-related, highly dense, and water-free triclinic phase with nominal composition CsAlSi2O6. At ambient temperature after pressure release, the Cs remains sequestered in a now monoclinic pollucite phase at close to 40 wt % and a favorably low Cs leaching rate under back-exchange conditions. This process thus efficiently combines the pressure-driven separation of Cs and I at ambient temperature with the subsequent sequestration of Cs under moderate pressures and temperatures in its preferred waste form suitable for long-term storage at ambient conditions. The zeolite pollucite CsAlSi2O6·H2O has been identified as a potential host material for nuclear waste remediation of anthropogenic (137)Cs due to its chemical and thermal stability, low leaching rate, and the large amount of Cs it can contain. The new water-free pollucite phase we characterize during our process will not display radiolysis of water during longterm storage while maintaining the Cs content and low leaching rate.

N-doped microporous carbons derived from direct carbonization of K+ exchanged meta-aminophenol–formaldehyde resin for superior CO2 sorption

Direct carbonization of K⁺ exchanged meta-aminophenol–formaldehyde resin afforded N-doped ultramicroporous carbons with high CO₂ uptakes.

Tuning the target composition of amine-grafted CPO-27-Mg for capture of CO2 under post-combustion and air filtering conditions: a combined experimental and computational study

A computational and experimental study is performed to determine the optimal composition that enhances the adsorption performance at low pressure.

Flexible and mechanically-stable MIL-101(Cr)@PFs for efficient benzene vapor and CO2adsorption

Novel MIL-101(Cr)@PF sheets with high uptakes for benzene and CO₂(10.29 and 2.13 mmol g⁻¹at 298 K, respectively) and excellent flexibility/mechanical stability were prepared by immobilizing MIL-101(Cr) crystals onto the modified pulp fibers (PFs).

Mesoporous poly(melamine-formaldehyde) solid sorbent for carbon dioxide capture

Feed the pore: A highly mesoporous melamine-formaldehyde resin is synthesized through a simple, one-step polycondensation reaction by using inexpensive and abundant common industrial chemicals. The material is demonstrated to have a high surface area and a well-defined pore structure. Its high density of CO2 binding pockets with low CO2 binding energy facilitates rapid and reversible CO2 sorption.