Porous Organic Polymers for Efficient and Selective SO2 Capture from CO2-rich Flue Gas.

The quest for effective technologies to reduce SO2 pollution is crucial due to its adverse effects on the environment and human health. Markedly, removing a ppm level of SO2 from CO2-containing waste gas is a persistent challenge, and current technologies suffer from low SO2/CO2 selectivity and energy-intensive regeneration processes. Here using the molecular building blocks approach and theoretical calculation, we constructed two porous organic polymers (POPs) encompassing pocket-like structures with exposed imidazole groups, promoting preferential interactions with SO2 from CO2-containing streams. Markedly, the evaluated POPs offer outstanding SO2/CO2 selectivity, high SO2 capacity, and an easy regeneration process, making it one of the best materials for SO2 capture. To gain better structural insights into the notable SO2 selectivity of the POPs, we used dynamic nuclear polarization NMR spectroscopy (DNP) and molecular modelling to probe the interactions between SO2 and POP adsorbents. The newly developed materials are poised to offer an energy-efficient and environment-friendly SO2 separation process while we are obliged to use fossil fuels for our energy needs.

Tuning Cellular Biological Functions Through the Controlled Release of NO from a Porous Ti-MOF.

Materials for the controlled release of nitric oxide (NO) are of interest for therapeutic applications. However, to date, many suffer from toxicity and stability issues, as well as poor performance. Herein, we propose a new NO adsorption/release mechanism through the formation of nitrites on the skeleton of a titanium-based metal-organic framework (MOF) that we named MIP-177, featuring a suitable set of properties for such an application: (i) high NO storage capacity (3 µmol mg-1solid ), (ii) excellent biocompatibility at therapeutic relevant concentrations (no cytotoxicity at 90 µg mL-1 for wound healing) due to its high stability in biological media (<9 % degradation in 72 hours) and (iii) slow NO release in biological media (≈2 hours for 90 % release). The prospective application of MIP-177 is demonstrated through NO-driven control of mitochondrial respiration in cells and stimulation of cell migration, paving the way for the design of new NO delivery systems for wound healing therapy.

Polymer Infiltration into Metal-Organic Frameworks in Mixed-Matrix Membranes Detected in Situ by NMR.

Solid-state NMR has been used to study mixed-matrix membranes (MMMs) prepared with a metal-organic framework (MOF, UiO-66) and two different high molecular weight polymers (PEO and PVDF). 13C and 1H NMR data provide overwhelming evidence that most UiO-66 organic linkers are within 1 nm of PEO, which indicates that PEO is homogeneously distributed throughout the MOF. Systematic changes in MOF 13C NMR peak positions and 1H NMR line widths, as well as dramatic reductions in the MOF 1H T1ρ relaxation times, are observed as the PEO content increases, and when the pores have been filled, a further increase in PEO results in the formation of semicrystalline PEO outside the UiO-66 particles. In contrast, similar studies on PVDF MMMs show that the polymer contacts only a small fraction (<20%) of the MOF linkers. Simulations confirm that PEO penetrates into UiO-66 more easily than does PVDF. These studies are among the first to provide experimental insights into MOF-polymer interactions in an MMM.

Enhanced Polymer Crystallinity in Mixed-Matrix Membranes Induced by Metal-Organic Framework Nanosheets for Efficient CO2 Capture.

The design and fabrication of novel mixed-matrix membranes (MMMs) with simultaneously enhanced gas permeability and selectivity are highly sought for the industrial deployment of membrane technology for large-scale CO2 capture and storage. Conventional isotropic bulky particle fillers often exhibit limited interfacial compatibility that eventually leads to significant selectivity loss in MMMs. Here, we report the incorporation of chemically stable metal-organic framework (MOF) nanosheets into a highly permeable polymer matrix to prepare defect-free MMMs. MOF nanosheets are homogeneously dispersed within the polymer matrix, owing to their high aspect ratios that improve the polymer-filler integration. The strong hydrogen bonding and π-π interactions between the two components not only enhance the interfacial compatibility but also favor the efficient polymer chain packing along the surface of MOF nanosheets, leading to enhanced polymer crystallinity as well as size-sieving capability of the membranes. The as-prepared MMMs demonstrate high CO2-selective separation performance, good antipressure, and antiaging abilities, thus offering new opportunities in developing advanced membranes for industrial gas separation applications.

DFT calculations for structural prediction and applications of intercalated lamellar compounds.

The intercalated layered materials are commonly built from structures complex enough to have large unit cells and, because of this, calculations of their electronic structures are very demanding in terms of memory, processing and time. Also, the versatility of these compounds enables the synthesis of a large number of derived materials difficult to characterize. Only in the last two decades, a combination of theoretical methodologies and advances in processing made density-functional theory (DFT) calculations quite interesting as an investigation tool for this family of materials. Since the intercalated layered or lamellar compounds correspond to a large group of important classes of materials and their experimental data were, and are still being, generated, only a small part of the data comes from electronic structure simulations. In this review, we have listed some relevant types of intercalated lamellar materials, the useful methodologies implemented in the standard suit of codes for DFT calculations and examples of the many applications of the calculations to the understanding of physical and chemical properties, to the planning of novel materials with desirable properties, and even to assist the structural characterization, by simulating complex results from nuclear magnetic resonance, vibrational spectroscopy and powder X-ray diffraction. In addition to the properties simulated directly as observables, other quantities such as density of states, partial charges and electronic density difference, provide relevant information about the materials and their behavior under diverse physical and chemical conditions. The combination of the geometric, electronic and vibrational structures also leads to the simulations of thermodynamic potentials, entropy and phase diagrams in the solid state. This significant ensemble of research tools makes DFT calculations very compelling and useful to gain new insights into innovation developments for intercalated lamellar materials.