Implementing Mesoporosity in Zeolitic Imidazolate Frameworks through Clip-Off Chemistry in Heterometallic Iron-Zinc ZIF-8

Bond breaking has emerged as a new tool to postsynthetically modify the pore structure in metal-organic frameworks since it allows us to obtain pore environments in structures that are inaccessible by other techniques. Here, we extend the concept of clip-off chemistry to archetypical ZIF-8, taking advantage of the different stabilities of the bonds between imidazolate and Zn and Fe metal atoms in heterometallic Fe-Zn-ZIF-8. We demonstrate that Fe centers can be removed selectively without affecting the backbone of the structure that is supported by the Zn atoms. This allows us to create mesopores within the highly stable ZIF-8 structure. The strategy presented, combined with control of the amount of iron centers incorporated into the structure, permits porosity engineering of ZIF materials and opens a new avenue for designing novel hierarchical porous frameworks.

The role of carbon capture, utilization, and storage for economic pathways that limit global warming to below 1.5°C

The 2021 Intergovernmental Panel on Climate Change (IPCC) report, for the first time, stated that CO₂ removal will be necessary to meet our climate goals. However, there is a cost to accomplish CO₂ removal or mitigation that varies by source. Accordingly, a sensible strategy to prevent climate change begins by mitigating emission sources requiring the least energy and capital investment per ton of CO₂, such as new emitters and long-term stationary sources. The production of CO₂-derived products should also start by favoring processes that bring to market high-value products with sufficient margin to tolerate a higher cost of goods.

Recent advancement in bimetallic metal organic frameworks (M’MOFs): Synthetic challenges and applications

Metal-organic frameworks (MOFs) is a burgeoning research field and has received increasing interest in recent years due to their inherent advantages of inorganic metal ions, range of organic linkers, tunable...

Capture and Reuse of Carbon Dioxide (CO2) for a Plastics Circular Economy: A Review

Plastic production has been increasing at enormous rates. Particularly, the socioenvironmental problems resulting from the linear economy model have been widely discussed, especially regarding plastic pieces intended for single use and disposed improperly in the environment. Nonetheless, greenhouse gas emissions caused by inappropriate disposal or recycling and by the many production stages have not been discussed thoroughly. Regarding the manufacturing processes, carbon dioxide is produced mainly through heating of process streams and intrinsic chemical transformations, explaining why first-generation petrochemical industries are among the top five most greenhouse gas (GHG)-polluting businesses. Consequently, the plastics market must pursue full integration with the circular economy approach, promoting the simultaneous recycling of plastic wastes and sequestration and reuse of CO2 through carbon capture and utilization (CCU) strategies, which can be employed for the manufacture of olefins (among other process streams) and reduction of fossil-fuel demands and environmental impacts. Considering the previous remarks, the present manuscript’s purpose is to provide a review regarding CO2 emissions, capture, and utilization in the plastics industry. A detailed bibliometric review of both the scientific and the patent literature available is presented, including the description of key players and critical discussions and suggestions about the main technologies. As shown throughout the text, the number of documents has grown steadily, illustrating the increasing importance of CCU strategies in the field of plastics manufacture.

Electronic structure benchmark calculations of CO2 fixing elementary chemical steps in RuBisCO using the projector-based embedding approach

Ribulose 1,5-bisphosphate carboxylase-oxygenase (RuBisCO) is the main enzyme involved in atmospheric carbon dioxide (CO₂ ) fixation in the biosphere. This enzyme catalyzes a set of five chemical steps that take place in the same active-site within magnesium (II) coordination sphere. Here, a set of electronic structure benchmark calculations have been carried out on a reaction path proposed by Gready et al. by means of the projector-based embedding approach. Activation and reaction energies for all main steps catalyzed by RuBisCO have been calculated at the MP2, SCS-MP2, CCSD, and CCSD(T)/aug-cc-pVDZ and cc-pVDZ levels of theory. The treatment of the magnesium cation with post-HF methods is explored to determine the nature of its involvement in the mechanism. With the high-level ab initio values as a reference, we tested the performance of a set of density functional theory (DFT) exchange-correlation (xc) functionals in reproducing the reaction energetics of RuBisCO carboxylase activity on a set of model fragments. Different DFT xc-functionals show large variation in activation and reaction energies. Activation and reaction energies computed at the B3LYP level are close to the reference SCS-MP2 results for carboxylation, hydration and protonation reactions. However, for the carbon-carbon bond dissociation reaction, B3LYP and other functionals give results that differ significantly from the ab initio reference values. The results show the applicability of the projector-based embedding approach to metalloenzymes. This technique removes the uncertainty associated with the selection of different DFT xc-functionals and so can overcome some of inherent limitations of DFT calculations, complementing, and potentially adding to modeling of enzyme reaction mechanisms with DFT methods.

Cation Doping Approach for Nanotubular Hydrosilicates Curvature Control and Related Applications

The past two decades have been marked by an increased interest in the synthesis and the properties of geoinspired hydrosilicate nanoscrolls and nanotubes. The present review considers three main representatives of this group: halloysite, imogolite and chrysotile. These hydrosilicates have the ability of spontaneous curling (scrolling) due to a number of crystal structure features, including the size and chemical composition differences between the sheets, (or the void in the gibbsite sheet and SiO2 tetrahedron, in the case of imogolite). Mineral nanoscrolls and nanotubes consist of the most abundant elements, like magnesium, aluminium and silicon, accompanied by uncontrollable amounts of impurities (other elements and phases), which hinder their high technology applications. The development of a synthetic approach makes it possible to not only to overcome the purity issues, but also to enhance the chemical composition of the nanotubular particles by controllable cation doping. The first part of the review covers some principles of the cation doping approach and proposes joint criteria for the semiquantitative prediction of morphological changes that occur. The second part focuses on some doping-related properties and applications, such as morphological control, uptake and release, magnetic and mechanical properties, and catalysis.

Cyclometalation of lanthanum(iii) based MOF for catalytic hydrogenation of carbon dioxide to formate

A novel metal–organic framework JMS-1 with rare topology zaz shows catalytic activity towards conversion of carbon dioxide to formate.

Construction of a hierarchical-structured MgO-carbon nanocomposite from a metal–organic complex for efficient CO2 capture and organic pollutant removal

A hierarchical-structured porous MgO/C nanocomposite derived from a metal–organic complex performs as a remarkable adsorbent for CO₂ adsorption and organic pollutant removal.

ZIF-8 as a Catalyst in Ethylene Oxide and Propylene Oxide Reaction with CO2 to Cyclic Organic Carbonates

CO2 is an important by-product in epoxides synthesis, accounting for 0.02% of worldwide greenhouse emissions. The CO2 cycloaddition to ethylene and propylene oxides is an important class of reactions due to the versatile nature of the corresponding organic carbonates as chemical feedstocks. We report that these reactions can be catalyzed by ZIF-8 (Zeolitic Imidazole Framework-8) in the absence of solvent or co-catalyst and in mild conditions (40 °C and 750 mbar). In situ infrared spectroscopy places the onset time for ethylene and propylene carbonate formation to 80 and 30 min, respectively. Although there is low catalytic activity, these findings suggest the possibility to cut the CO2 emissions from epoxides production through their direct conversion to these highly valuable chemical intermediates, eliminating de facto energetically demanding steps as the CO2 capture and storage.

Electronic structure benchmark calculations of inorganic and biochemical carboxylation reactions

Carboxylation reactions represent a very special class of chemical reactions that is characterized by the presence of a carbon dioxide (CO₂ ) molecule as reactive species within its global chemical equation. These reactions work as fundamental gear to accomplish the CO₂ fixation and thus to build up more complex molecules through different technological and biochemical processes. In this context, a correct description of the CO₂ electronic structure turns out to be crucial to study the chemical and electronic properties associated with this kind of reactions. Here, a systematic study of CO₂ electronic structure and its contribution to different carboxylation reaction electronic energies has been carried out by means of several high-level ab initio post-Hartree Fock (post-HF) and density functional theory (DFT) calculations for a set of biochemistry and inorganic systems. We have found that for a correct description of the CO₂ electronic correlation energy it is necessary to include post-CCSD(T) contributions (beyond the gold standard). These high-order excitations are required to properly describe the interactions of the four π-electrons associated with the two degenerated π-molecular orbitals of the CO₂ molecule. Likewise, our results show that in some reactions it is possible to obtain accurate reaction electronic energy values with computationally less demanding methods when the error in the electronic correlation energy compensates between reactants and products. Furthermore, the provided post-HF reference values allowed to validating different DFT exchange-correlation functionals combined with different basis sets for chemical reactions that are relevant in biochemical CO₂ fixing enzymes. © 2019 Wiley Periodicals, Inc.

Communication: Photoinduced carbon dioxide binding with surface-functionalized silicon quantum dots

Nowadays, the search for efficient methods able to reduce the high atmospheric carbon dioxide concentration has turned into a very dynamic research area. Several environmental problems have been closely associated with the high atmospheric level of this greenhouse gas. Here, a novel system based on the use of surface-functionalized silicon quantum dots (sf-SiQDs) is theoretically proposed as a versatile device to bind carbon dioxide. Within this approach, carbon dioxide trapping is modulated by a photoinduced charge redistribution between the capping molecule and the silicon quantum dots (SiQDs). The chemical and electronic properties of the proposed SiQDs have been studied with a Density Functional Theory and Density Functional Tight-Binding (DFTB) approach along with a time-dependent model based on the DFTB framework. To the best of our knowledge, this is the first report that proposes and explores the potential application of a versatile and friendly device based on the use of sf-SiQDs for photochemically activated carbon dioxide fixation.

In Situ Observation of Carbon Dioxide Capture on Pseudo-Liquid Eutectic Mixture-Promoted Magnesium Oxide

Eutectic mixtures of alkali nitrates are known to increase the sorption capacity and kinetics of MgO-based sorbents. Underlying principles and mechanisms for CO₂ capture on such sorbents have already been established; however, real-time observation of the system was not yet accomplished. In this work, we present the direct-observation of the CO₂ capture phenomenon on a KNO₃-LiNO₃ eutectic mixture (EM)-promoted MgO sample, denoted as KLM, via in situ transmission electron microscopy (in situ TEM). Results revealed that the pseudoliquid EM undergoes structural rearrangement as MgCO₃ evolves from the surface of MgO, resulting in surface roughening and evolution of cloudy structures that stay finely distributed after regeneration. From this, we propose a nucleation and structural rearrangement scheme for MgCO₃ and EM, which involves the rearrangement of bulk EM to evenly distributed EM clusters due to MgCO₃ saturation as adsorption proceeds. We also conducted studies on the interface between EM over solid MgO and MgCO₃ formed during sorption, which further clarifies the interaction between MgO and EM. This study provides better insight into the sorption and regeneration mechanism, as well as the structural rearrangements involved in EM-promoted sorbents by basing not only on intrinsic evolutions but also on real-time observation of the system as a whole.

Sensing and capture of toxic and hazardous gases and vapors by metal–organic frameworks

This review summaries recent progress in the luminescent detection and adsorptive removal of harmful gases and vapors by metal–organic frameworks, as well as the principles and strategies guiding the design of these materials.

On the structure of superbasic (MgO)n sites solvated in a faujasite zeolite

Theory and experiment reveal the structure of magnesium oxide nanoclusters in a superbasic faujasite zeolite.

Hierarchical Nanocomposite by the Integration of Reduced Graphene Oxide and Amorphous Carbon with Ultrafine MgO Nanocrystallites for Enhanced CO2 Capture

Exploring efficient and low-cost solid sorbents is essential for carbon capture and storage. Herein, a novel class of high-performance CO₂ adsorbent (rGO@MgO/C) is engineered based on the controllable integration of reduced graphene oxide (rGO), amorphous carbon, and MgO nanocrystallites. The optimized rGO@MgO/C nanocomposite exhibits remarkable CO₂ capture capacity (up to 31.5 wt % at 27 °C, 1 bar CO₂, and 22.5 wt % under the simulated flue gas), fast sorption rate, and strong process durability. The enhanced capture capability of CO₂ is the best among all of the MgO-based sorbents reported so far. The high performance of rGO@MgO/C nanocomposite can be ascribed to the hierarchical architecture and special physicochemical features, including the sheet-on-sheet sandwich-like structure, ultrathin nanosheets with abundant nanopores, large surface area, and highly dispersed ultrafine MgO nanocrystallites (ca. 3 nm in size), together with the rGO sheets and in situ generated amorphous carbon that serve as a dual carbon support and protectant system with which to prevent MgO nanocrystallites from agglomeration. In addition, the CO₂-uptake capacity at intermediate temperature (e.g., 350 °C) can be further improved threefold through alkali metal salt promotion treatment. This work provides a facile and effective strategy with which to engineer advanced graphene-based functional nanocomposites with rationally designed compositions and architectures for potential applications in the field of gas storage and separation.

Synthesis, Structure, and Reactivity of a Terminal Magnesium Hydride Compound with a Carbatrane Motif, [TismPriBenz]MgH: A Multifunctional Catalyst for Hydrosilylation and Hydroboration

The tris[(1-isopropylbenzimidazol-2-yl)dimethylsilyl)]methyl ligand, [Tism^PriBenz], has been employed to form the magnesium carbatrane compound, [Tism^PriBenz]MgH, which possesses a terminal hydride ligand. Specifically, [Tism^PriBenz]MgH is obtained via the reaction of [Tism^PriBenz]MgMe with PhSiH₃. The reactivity of [Tism^PriBenz]MgMe and [Tism^PriBenz]MgH allows access to a variety of other structurally characterized carbatrane derivatives, including [Tism^PriBenz]MgX [X = F, Cl, Br, I, SH, N(H)Ph, CH(Me)Ph, O₂CMe, S₂CMe]. In addition, [Tism^PriBenz]MgH is a catalyst for (i) hydrosilylation and hydroboration of styrene to afford the Markovnikov products, Ph(Me)C(H)SiH₂Ph and Ph(Me)C(H)Bpin, and (ii) hydroboration of carbodiimides and pyridine to form N-boryl formamidines and N-boryl 1,4- and 1,2-dihydropyridines, respectively.

Synthetic Architecture of MgO/C Nanocomposite from Hierarchical-Structured Coordination Polymer toward Enhanced CO2 Capture

Highly efficient, durable, and earth-abundant solid sorbents are of paramount importance for practical carbon capture, storage, and utilization. Here, we report a novel and facile two-step strategy to synthesize a group of hierarchically structured porous MgO/C nanocomposites using flowerlike Mg-containing coordination polymer as a precursor. The new nanocomposites exhibit superb CO₂ capture performance with sorption capacity up to 30.9 wt % (at 27 °C, 1 bar CO₂), fast sorption kinetics, and long cycling life. Importantly, the achieved capacity is >14 times higher than that of commercial MgO, and favorably exceeds the highest value recorded to date for MgO-based sorbents under similar operating conditions. On the basis of the morphological and textural property analysis, together with CO₂ sorption mechanism study using CO₂-TPD and DRIFT techniques, the outstanding performance in CO₂ uptake originates from unique features of this type of sorbent materials, which include hierarchical architecture, porous building blocks of nanosheets, high specific surface area (ca. 300 m²/g), evenly dispersed MgO nanocrystallites (ca. 3 nm) providing abundant active sites, and the in situ generated carbon matrix that acts as a stabilizer to prevent the growth and agglomeration of MgO crystallites. The nanocomposite system developed in this work shows good potential for future low-cost CO₂ abatement and utilization.

CO2 Capture in Dry and Wet Conditions in UTSA-16 Metal-Organic Framework

Water is the strongest competitor to CO₂ in the adsorption on microporous materials, affecting their performances as CO₂ scrubbers in processes such as postcombustion carbon capture. The metal-organic framework (MOF) UTSA-16 is considered a promising material for its capacity to efficiently capture CO₂ in large quantities, thanks to the presence of open metal sites (OMSs). It is here shown that UTSA-16 is also able to desorb fully water already at room temperature. This property is unique from all the other materials with OMSs reported so far. UTSA-16 retains indeed the 70% of its CO₂ separation capacity after admittance of water in a test flow, created to simulate the emissions from a real postcombustion carbon-capture process. This important aspect not yet observed for any other amine-free material, associated with a high material stability-tested for 160 cycles-and a small temperature swing necessary for regeneration, places UTSA-16 in the restrict number of systems with a real technological future for CO₂ separation.

Hierarchically structured magnesium based oxides: synthesis strategies and applications in organic pollutant remediation

In this highlight, we review the design and formation of MgO based hierarchical structures and cover some selected examples on their applications in adsorption of organic contaminants.

Solvent-Driven Gate Opening in MOF-76-Ce: Effect on CO2 Adsorption

A cerium-based metal-organic framework with MOF-76 topology has been synthesized by a very simple and fast solvothermal method that has been tested for a one gram yield. Variable-temperature powder XRD and X-ray absorption data, analyzed by Rietveld and multiple-scattering extended X-ray absorption fine-structure methods, revealed high thermal stability and the presence of three different stable structures. X-ray absorption near-edge structure and FTIR spectroscopy probed the presence of cerium(III), which was characterized by coordinatively unsaturated sites that, however, played no major role in carbon dioxide adsorption. The material revealed excellent carbon dioxide adsorption properties: the highest gravimetric capacity of 15 wt% was observed at 1.1 bar in the case of the sample activated at 250 °C in vacuum, whereas the strongest interaction energy of 35 kJ mol(-1) was observed for the sample activated at 150 °C. Negligible nitrogen uptake of the sample activated at 150 °C indicates that this material is a promising candidate for nitrogen/carbon dioxide separation purposes.

Experimental Investigation and Simplistic Geochemical Modeling of CO₂ Mineral Carbonation Using the Mount Tawai Peridotite

In this work, the potential of CO₂ mineral carbonation of brucite (Mg(OH)₂) derived from the Mount Tawai peridotite (forsterite based (Mg)₂SiO₄) to produce thermodynamically stable magnesium carbonate (MgCO₃) was evaluated. The effect of three main factors (reaction temperature, particle size, and water vapor) were investigated in a sequence of experiments consisting of aqueous acid leaching, evaporation to dryness of the slurry mass, and then gas-solid carbonation under pressurized CO₂. The maximum amount of Mg converted to MgCO₃ is ~99%, which occurred at temperatures between 150 and 175 °C. It was also found that the reduction of particle size range from >200 to <75 µm enhanced the leaching rate significantly. In addition, the results showed the essential role of water vapor in promoting effective carbonation. By increasing water vapor concentration from 5 to 10 vol %, the mineral carbonation rate increased by 30%. This work has also numerically modeled the process by which CO₂ gas may be sequestered, by reaction with forsterite in the presence of moisture. In both experimental analysis and geochemical modeling, the results showed that the reaction is favored and of high yield; going almost to completion (within about one year) with the bulk of the carbon partitioning into magnesite and that very little remains in solution.

Catalytic hydrogenation of CO2 to methanol in a Lewis pair functionalized MOF

Capture and conversion of CO₂ to methanol using a renewable source of H₂ is a promising way to reduce net CO₂ emissions while producing valuable fuels.

New insights into UTSA-16

High CO₂ volumetric capacity of UTSA-16 is exclusively driven by the formation of direct adducts between CO₂ and K⁺ sites.

Nanostructure and pore size control of template-free synthesised mesoporous magnesium carbonate

The structure of mesoporous magnesium carbonate (MMC) first presented in 2013 is investigated using a bottom-up approach.