An amino acid based system for CO2 capture and catalytic utilization to produce formates

Herein, we report a novel amino acid based reaction system for CO₂ capture and utilization (CCU) to produce formates in the presence of the naturally occurring amino acid l-lysine. Utilizing a specific ruthenium-based catalyst system, hydrogenation of absorbed carbon dioxide occurs with high activity and excellent productivity. Noteworthy, following the CCU concept, CO₂ can be captured from ambient air in the form of carbamates and converted directly to formates in one-pot (TON > 50 000). This protocol opens new potential for transforming captured CO₂ from ambient air to C1-related products.

A novel amino acid based reaction system for CO₂ capture and utilization (CCU) to produce formates is presented applying a ruthenium-based catalyst. Noteworthy, CO₂ can be captured from ambient air and converted to formates in one-pot (TON > 50 000).     

Accelerated reactions of amines with carbon dioxide driven by superacid at the microdroplet interface

Microdroplets display distinctive interfacial chemistry, manifested as accelerated reactions relative to those observed for the same reagents in bulk. Carbon dioxide undergoes C–N bond formation reactions with amines at the interface of droplets to form carbamic acids. Electrospray ionization mass spectrometry displays the reaction products in the form of the protonated and deprotonated carbamic acid. Electrosonic spray ionization (ESSI) utilizing carbon dioxide as nebulization gas, confines reaction to the gas–liquid interface where it proceeds much faster than in the bulk. Intriguingly, trace amounts of water accelerate the reaction, presumably by formation of superacid or superbase at the water interface. The suggested mechanism of protonation of CO₂ followed by nucleophilic attack by the amine is analogous to that previously advanced for imidazole formation from carboxylic acids and diamines.

Microdroplets display distinctive interfacial chemistry, manifested as accelerated reactions relative to those observed for the same reagents in bulk.     

Role of ion-selective membranes in the carbon balance for CO2 electroreduction via gas diffusion electrode reactor designs

In this work, the effect of ion-selective membranes on the detailed carbon balance was systematically analyzed for high-rate CO₂ reduction in GDE-type flow electrolyzers. By using different ion-selective membranes, we show nearly identical catalytic selectivity for CO₂ reduction, which is primarily due to a similar local reaction environment created at the cathode/electrolyte interface via the introduction of a catholyte layer. In addition, based on a systematic exploration of gases released from electrolytes and the dynamic change of electrolyte speciation, we demonstrate the explicit discrepancy in carbon balance paths for the captured CO₂ at the cathode/catholyte interface via reaction with OH⁻ when using different ion-selective membranes: (i) the captured CO₂ could be transported through an anion exchange membrane in the form of CO₃²⁻, subsequently releasing CO₂ along with O₂ in the anolyte, and (ii) with a cation exchange membrane, the captured CO₂ would be accumulated in the catholyte in the form of CO₃²⁻, while (iii) with the use of a bipolar membrane, the captured CO₂ could be released at the catholyte/membrane interface in the form of gaseous CO₂. The unique carbon balance path for each type of membrane is linked to ion species transported through the membranes.

In this work, the effect of ion-selective membranes on the detailed carbon balance was systematically analyzed for high-rate CO₂ reduction in GDE-type flow electrolyzers.     

Stereodivergent synthesis of β-iodoenol carbamates with CO2via photocatalysis

Photocatalytic conversion of carbon dioxide (CO₂) into value-added chemicals is of great significance from the viewpoint of green chemistry and sustainable development. Here, we report a stereodivergent synthesis of β-iodoenol carbamates through a photocatalytic three-component coupling of ethynylbenziodoxolones, CO₂ and amines. By choosing appropriate photocatalysts, both Z- and E-isomers of β-iodoenol carbamates, which are difficult to prepare using existing methods, can be obtained stereoselectively. This transformation featured mild conditions, excellent functional group compatibility and broad substrate scope. The potential synthetic utility of this protocol was demonstrated by late-stage modification of bioactive molecules and pharmaceuticals as well as by elaborating the products to access a wide range of valuable compounds. More importantly, this strategy could provide a general and practical method for stereodivergent construction of trisubstituted alkenes such as triarylalkenes, which represents a fascinating challenge in the field of organic chemistry research. A series of mechanism investigations revealed that the transformation might proceed through a charge-transfer complex which might be formed through a halogen bond.

Stereodivergent synthesis of β-iodoenol carbamates was achieved via a photocatalytic three-component coupling reaction of ethynylbenziodoxolones, CO₂ and amines.     

Recent advances in single atom catalysts for the electrochemical carbon dioxide reduction reaction

The electrochemical carbon dioxide reduction reaction (CO₂RR) offers a promising solution to mitigate carbon emission and at the same time generate valuable carbonaceous chemicals/fuels. Single atom catalysts (SACs) are encouraging to catalyze the electrochemical CO₂RR due to the tunable electronic structure of the central metal atoms, which can regulate the adsorption energy of reactants and reaction intermediates. Moreover, SACs form a bridge between homogeneous and heterogeneous catalysts, providing an ideal platform to explore the reaction mechanism of electrochemical reactions. In this review, we first discuss the strategies for promoting the CO₂RR performance, including suppression of the hydrogen evolution reaction (HER), generation of C₁ products and formation of C₂₊ products. Then, we summarize the recent developments in regulating the structure of SACs toward the CO₂RR based on the above aspects. Finally, several issues regarding the development of SACs for the CO₂RR are raised and possible solutions are provided.

The electrochemical carbon dioxide reduction reaction (CO₂RR) offers a promising solution to mitigate carbon emission and at the same time generate valuable carbonaceous chemicals/fuels.     

Insights into amine-based CO<Subscript>2</Subscript> capture: an ab initio self-consistent reaction field investigation

Ab initio many-body perturbation theory (MP2/6-311++G(,dp)), density functional theory (B3LYP/6-31++G(d,p)) and self-consistent reaction field (IEF-PCM UA HF/6-31G(d)) calculations have been used to study the CO₂ capture reagents NH₃, 2-hydroxyethylamine (MEA), diaminoethane (EN), 2-amino-1-propanol (2A1P), diethanolamine (DEA), N-methyl-2-hydroxyethylamine (N-methylMEA), 2-amino-2-methyl-1-propanol (AMP), trishydroxymethylaminomethane (tris), piperazine (PZ) and piperidine (PD). This study involved full conformational searches of the capture amines in their native and protonated forms, and their carbamic acid and carbamate derivatives. Using this data, we were able to compute Boltzmann-averaged thermodynamic values for the amines, carbamates and carbamic acid derivatives, as well as equilibrium constants for a series of ‘universal’ aqueous capture reactions. Important findings include (i) relative pK _a values for the carbamic acid derivatives are a useful measure of carbamate stability, due to a particular chemical resonance which is also manifest in short computed N–CO₂H bonds at both levels of theory, (ii) the computational results for sterically hindered amines such as AMP and tris are consistent with these species forming carbamates which readily hydrolyse and (iii) the amine-catalysed reaction between OH⁻ and CO₂ to generate bicarbonate correlates with amine pK _a. Thermodynamic data from the ab initio computations predicts that the heterocycles PD and PZ and the acyclic sorbent EN are good choices for a capture solvent. AMP and tris perform poorly in comparison.     

From CO2 activation to catalytic reduction: a metal-free approach

Over exploitation of natural resources and human activities are relentlessly fueling the emission of CO₂ in the atmosphere. Accordingly, continuous efforts are required to find solutions to address the issue of excessive CO₂ emission and its potential effects on climate change. It is imperative that the world looks towards a portfolio of carbon mitigation solutions, rather than a single strategy. In this regard, the use of CO₂ as a C1 source is an attractive strategy as CO₂ has the potential to be a great asset for the industrial sector and consumers across the globe. In particular, the reduction of CO₂ offers an alternative to fossil fuels for various organic industrial feedstocks and fuels. Consequently, efficient and scalable approaches for the reduction of CO₂ to products such as methane and methanol can generate value from its emissions. Accordingly, in recent years, metal-free catalysis has emerged as a sustainable approach because of the mild reaction conditions by which CO₂ can be reduced to various value-added products. The metal-free catalytic reduction of CO₂ offers the development of chemical processes with low cost, earth-abundant, non-toxic reagents, and low carbon-footprint. Thus, this perspective aims to present the developments in both the reduction and reductive functionalization chemistry of CO₂ during the last decade using various metal-free catalysts.

This review article documents the key developments in the metal-free catalytic reduction of CO₂ into various energy intensive chemicals and fuels, and reductive functionalization of CO₂ for the formation of new C–N bonds.     

Indirect reduction of CO2 and recycling of polymers by manganese-catalyzed transfer hydrogenation of amides,carbamates, urea derivatives,and polyurethanes

The reduction of polar bonds, in particular carbonyl groups, is of fundamental importance in organic chemistry and biology. Herein, we report a manganese pincer complex as a versatile catalyst for the transfer hydrogenation of amides, carbamates, urea derivatives, and even polyurethanes leading to the corresponding alcohols, amines, and methanol as products. Since these compound classes can be prepared using CO₂ as a C1 building block the reported reaction represents an approach to the indirect reduction of CO₂. Notably, these are the first examples on the reduction of carbamates and urea derivatives as well as on the C–N bond cleavage in amides by transfer hydrogenation. The general applicability of this methodology is highlighted by the successful reduction of 12 urea derivatives, 26 carbamates and 11 amides. The corresponding amines, alcohols and methanol were obtained in good to excellent yields up to 97%. Furthermore, polyurethanes were successfully converted which represents a viable strategy towards a circular economy. Based on control experiments and the observed intermediates a feasible mechanism is proposed.

A Mn–PNP complex proved to be a suitable catalyst for the transfer hydrogenation of amides, carbamates, urea derivatives and even polyurethanes.     

Spatial-confinement induced electroreduction of CO and CO2 to diols on densely-arrayed Cu nanopyramids

The electroreduction of carbon dioxide (CO₂) and carbon monoxide (CO) to liquid alcohol is of significant research interest. This is because of a high mass-energy density, readiness for transportation and established utilization infrastructure. Current success is mainly around monohydric alcohols, such as methanol and ethanol. There exist few reports on converting CO₂ or CO to higher-valued diols such as ethylene glycol (EG; (CH₂OH)₂). The challenge to producing diols lies in the requirement to retain two oxygen atoms in the compound. Here for the first time, we demonstrate that densely-arrayed Cu nanopyramids (Cu-DAN) are able to retain two oxygen atoms for hydroxyl formation. This results in selective electroreduction of CO₂ or CO to diols. Density Functional Theory (DFT) computations highlight that the unique spatial-confinement induced by Cu-DAN is crucial to selectively generating EG through a new reaction pathway. This structure promotes C–C coupling with a decreased reaction barrier. Following C–C coupling the structure facilitates EG production by (1) retaining oxygen and promoting the *COH–CHO pathway, which is a newly identified pathway toward ethylene glycol production; and, (2) suppressing the carbon–oxygen bond breaking in intermediate *CH₂OH–CH₂O and boosting hydrogenation to EG. Our findings will be of immediate interest to researchers in the design of highly active and selective CO₂ and CO electroreduction to diols.

Densely-arrayed Cu nanopyramids have spatial confinement induced by the additional Cu–O bond. This promotes C–C coupling, regulates post-C–C coupling, and retains both oxygen atoms in an alternative pathway toward ethylene glycol formation from CO.     

Next steps for solvent-based CO2 capture; integration of capture,conversion, and mineralisation

In this perspective, we detail how solvent-based carbon capture integrated with conversion can be an important element in a net-zero emission economy. Carbon capture and utilization (CCU) is a promising approach for at-scale production of green CO₂-derived fuels, chemicals and materials. The challenge is that CO₂-derived materials and products have yet to reach market competitiveness because costs are significantly higher than those from conventional means. We present here the key to making CO₂-derived products more efficiently and cheaper, integration of solvent-based CO₂ capture and conversion. We present the fundamentals and benefits of integration within a changing energy landscape (i.e., CO₂ from point source emissions transitioning to CO₂ from the atmosphere), and how integration could lead to lower costs and higher efficiency, but more importantly how CO₂ altered in solution can offer new reactive pathways to produce products that cannot be made today. We discuss how solvents are the key to integration, and how solvents can adapt to differing needs for capture, conversion and mineralisation in the near, intermediate and long term. We close with a brief outlook of this emerging field of study, and identify critical needs to achieve success, including establishing a green-premium for fuels, chemicals, and materials produced in this manner.

In this perspective, we detail how solvent-based carbon capture integrated with conversion can be an important element in a net-zero emission economy.     

Polyoxometalate-based electron transfer modulation for efficient electrocatalytic carbon dioxide reduction

The electrocatalytic carbon dioxide (CO₂) reduction reaction (CO₂RR) involves a variety of electron transfer pathways, resulting in poor reaction selectivity, limiting its use to meet future energy requirements. Polyoxometalates (POMs) can both store and release multiple electrons in the electrochemical process, and this is expected to be an ideal “electron switch” to match with catalytically active species, realize electron transfer modulation and promote the activity and selectivity of the electrocatalytic CO₂RR. Herein, we report a series of new POM-based manganese-carbonyl (MnL) composite CO₂ reduction electrocatalysts, whereby SiW₁₂–MnL exhibits the most remarkable activity and selectivity for CO₂RR to CO, resulting in an increase in the faradaic efficiency (FE) from 65% (MnL) to a record-value of 95% in aqueous electrolyte. A series of control electrochemical experiments, photoluminescence spectroscopy (PL), transient photovoltage (TPV) experiments, and density functional theory (DFT) calculations revealed that POMs act as electronic regulators to control the electron transfer process from POM to MnL units during the electrochemical reaction, enhancing the selectivity of the CO₂RR to CO and depressing the competitive hydrogen evolution reaction (HER). This work demonstrates the significance of electron transfer modulation in the CO₂RR and suggests a new idea for the design of efficient electrocatalysts towards CO₂RR.

Polyoxometalates as electron regulators to promote the carbonyl manganese (MnL) electrocatalyst for highly efficient CO₂ reduction in aqueous electrolyte.     

Probing the local activity of CO2 reduction on gold gas diffusion electrodes: effect of the catalyst loading and CO2 pressure

Large scale CO₂ electrolysis can be achieved using gas diffusion electrodes (GDEs), and is an essential step towards broader implementation of carbon capture and utilization strategies. Different variables are known to affect the performance of GDEs. Especially regarding the catalyst loading, there are diverging trends reported in terms of activity and selectivity, e.g. for CO₂ reduction to CO. We have used shear–force based Au nanoelectrode positioning and scanning electrochemical microscopy (SECM) in the surface-generation tip collection mode to evaluate the activity of Au GDEs for CO₂ reduction as a function of catalyst loading and CO₂ back pressure. Using a Au nanoelectrode, we have locally measured the amount of CO produced along a catalyst loading gradient under operando conditions. We observed that an optimum local loading of catalyst is necessary to achieve high activities. However, this optimum is directly dependent on the CO₂ back pressure. Our work does not only present a tool to evaluate the activity of GDEs locally, it also allows drawing a more precise picture regarding the effect of catalyst loading and CO₂ back pressure on their performance.

Large scale CO₂ electrolysis can be achieved using gas diffusion electrodes (GDEs), and is an essential step towards broader implementation of carbon capture and utilization strategies.     

A rationally designed two-dimensional MoSe2/Ti2CO2 heterojunction for photocatalytic overall water splitting: simultaneously suppressing electron–hole recombination and photocorrosion

Electron–hole recombination and photocorrosion are two challenges that seriously limit the application of two-dimensional (2D) transition metal dichalcogenides (TMDs) for photocatalytic water splitting. In this work, we propose a 2D van der Waals MoSe₂/Ti₂CO₂ heterojunction that features promising resistance to both electron–hole recombination and photocorrosion existing in TMDs. By means of first-principles calculations, the MoSe₂/Ti₂CO₂ heterojunction is demonstrated to be a direct Z-scheme photocatalyst for overall water splitting with MoSe₂ and Ti₂CO₂ serving as photocatalysts for hydrogen and oxygen evolution reactions, respectively, which is beneficial to electron–hole separation. The ultrafast migration of photo-generated holes from MoSe₂ to Ti₂CO₂ as well as the anti-photocorrosion ability of Ti₂CO₂ are responsible for photocatalytic stability. This heterojunction is experimentally reachable and exhibits a high solar-to-hydrogen efficiency of 12%. The strategy proposed here paves the way for developing 2D photocatalysts for water splitting with high performance and stability in experiments.

The two challenges of electron–hole recombination and photocorrosion for two-dimensional transition metal dichalcogenides in the application of photocatalytic water splitting are simultaneously suppressed by rational design of heterojunctions.     

Utilization of N,N‐Dialkylcarbamic Acid Derived from Secondary Amines and Supercritical Carbon Dioxide: Stereoselective Synthesis of Z Alkenyl Carbamates with a CO2‐Soluble Ruthenium–P(OC2H5)3 Catalyst

Reversible transformation of diethylamine ( 1 ) and supercritical carbon dioxide (scCO₂) into N,N‐diethylcarbamic acid ( 2 ) was confirmed by direct acquisition of ¹H and ¹³C{¹H} NMR spectra. The equilibrium between 1 +CO₂ and 2 is strongly influenced by conditions of the supercritical state. Low temperature favors formation of carbamic acid, whereas high temperature causes decarboxylation. On the basis of the spectroscopic results of carbamic acid formation under scCO₂ conditions, the ruthenium‐catalyzed formation of alkenyl carbamates from terminal alkynes, 1 , and carbon dioxide was investigated to demonstrate the useful transformation of elusive carbamic acids. Selectivity toward the CO₂‐fixation products over enynes obtained by dimerization of the alkyne substrates was improved by the use of scCO₂ as a reaction medium. In particular, a CO₂‐soluble ruthenium complex, trans‐[RuCl₂{P(OC₂H₅)₃}₄], was found to be effective in affording Z alkenyl carbamates with high stereoselectivity.     

Fast oxygen ion migration in Cu–In–oxide bulk and its utilization for effective CO2 conversion at lower temperature

Efficient activation of CO₂ at low temperature was achieved by reverse water–gas shift via chemical looping (RWGS-CL) by virtue of fast oxygen ion migration in a Cu–In structured oxide, even at lower temperatures. Results show that a novel Cu–In₂O₃ structured oxide can show a remarkably higher CO₂ splitting rate than ever reported. Various analyses revealed that RWGS-CL on Cu–In₂O₃ is derived from redox between Cu–In₂O₃ and Cu–In alloy. Key factors for high CO₂ splitting rate were fast migration of oxide ions in the alloy and the preferential oxidation of the interface of alloy–In₂O₃ in the bulk of the particles. The findings reported herein can open up new avenues to achieve effective CO₂ conversion at lower temperatures.

Efficient activation of CO₂ at low temperature was achieved by reverse water–gas shift via chemical looping (RWGS-CL) by virtue of fast oxygen ion migration in a Cu–In structured oxide, even at lower temperatures.     

H2/CO2 separations in multicomponent metal-adeninate MOFs with multiple chemically distinct pore environments

Metal–organic frameworks constructed from multiple (≥3) components often exhibit dramatically increased structural complexity compared to their 2 component (1 metal, 1 linker) counterparts, such as multiple chemically unique pore environments and a plurality of diverse molecular diffusion pathways. This inherent complexity can be advantageous for gas separation applications. Here, we report two isoreticular multicomponent MOFs, bMOF-200 (4 components; Cu, Zn, adeninate, pyrazolate) and bMOF-201 (3 components; Zn, adeninate, pyrazolate). We describe their structures, which contain 3 unique interconnected pore environments, and we use Kohn–Sham density functional theory (DFT) along with the climbing image nudged elastic band (CI-NEB) method to predict potential H₂/CO₂ separation ability of bMOF-200. We examine the H₂/CO₂ separation performance using both column breakthrough and membrane permeation studies. bMOF-200 membranes exhibit a H₂/CO₂ separation factor of 7.9. The pore space of bMOF-201 is significantly different than bMOF-200, and one molecular diffusion pathway is occluded by coordinating charge-balancing formate and acetate anions. A consequence of this structural difference is reduced permeability to both H₂ and CO₂ and a significantly improved H₂/CO₂ separation factor of 22.2 compared to bMOF-200, which makes bMOF-201 membranes competitive with some of the best performing MOF membranes in terms of H₂/CO₂ separations.

Tailorable multicomponent MOFs and MOF membranes for efficient H₂/CO₂ separation.     

Direct air capture of CO2via crystal engineering

This article presents a perspective view of the topic of direct air capture (DAC) of carbon dioxide and its role in mitigating climate change, focusing on a promising approach to DAC involving crystal engineering of metal–organic and hydrogen-bonded frameworks. The structures of these crystalline materials can be easily elucidated using X-ray and neutron diffraction methods, thereby allowing for systematic structure–property relationships studies, and precise tuning of their DAC performance.

A perspective view of direct air capture (DAC) of CO₂ and its role in mitigating climate change is presented. The article focuses on a promising approach to DAC involving crystal engineering of metal–organic and hydrogen-bonded frameworks.     

Co‐Catalyst‐Free Chemical Fixation of CO2 into Cyclic Carbonates by using Metal‐Organic Frameworks as Efficient Heterogeneous Catalysts

The concentration of carbon dioxide (CO₂) in the atmosphere is increasing at an alarming rate resulting in undesirable environmental issues. To mitigate this growing concentration of CO₂, selective carbon capture and storage/sequestration (CCS) are being investigated intensively. However, CCS technology is considered as an expensive and energy‐intensive process. In this context, selective carbon capture and utilization (CCU) as a C1 feedstock to synthesize value‐added chemicals and fuels is a promising step towards lowering the concentration of the atmospheric CO₂ and for the production of high‐value chemicals. Towards this direction, several strategies have been developed to convert CO₂, a Greenhouse gas (GHG) into useful chemicals by forming C?N, C?O, C?C, and C?H bonds. Among the various CO₂ functionalization processes known, the cycloaddition of CO₂ to epoxides has gained considerable interest owing to its 100% atom‐economic nature producing cyclic carbonates or polycarbonates in high yield and selectivity. Among the various classes of catalysts studied for cycloaddition of CO₂ to cyclic carbonates, porous metal‐organic frameworks (MOFs) have gained a special interest due to their modular nature facilitating the introduction of a high density of Lewis acidic (LA) and CO₂‐philic Lewis basic (LB) functionalities. However, most of the MOF‐based catalysts reported for cycloaddition of CO₂ to respective cyclic carbonates in high yields require additional co‐catalyst, say tetra‐n‐butylammonium bromide (TBAB). On the contrary, the co‐catalyst‐free conversion of CO₂ using rationally designed MOFs composed of both LA and LB sites is relatively less studied. In this review, we provide a comprehensive account of the research progress in the design of MOF based catalysts for environment‐friendly, co‐catalyst‐free fixation of CO₂ into cyclic carbonates.     

Soluble,crystalline, and thermally stable alkali CO2− and carbonite (CO22−) clusters supported by cyclic(alkyl)(amino) carbenes

The mono- and dianions of CO₂ (i.e., CO₂⁻ and CO₂²⁻) have been studied for decades as both fundamentally important oxycarbanions (anions containing only C and O atoms) and as critical species in CO₂ reduction and fixation chemistry. However, CO₂ anions are highly unstable and difficult to study. As such, examples of stable compounds containing these ions are extremely limited; the unadulterated alkali salts of CO₂ (i.e., MCO₂, M₂CO₂, M = alkali metal) decompose rapidly above 15 K, for example. Herein we report the chemical reduction of a cyclic (alkyl)(amino) carbene (CAAC) adduct of CO₂ at room temperature by alkali metals, which results in the formation of CAAC-stabilized alkali CO₂⁻ and CO₂²⁻ clusters. One-electron reduction of CAAC–CO₂ adduct (1) with lithium, sodium or potassium metal yields stable monoanionic radicals [M(CAAC–CO₂)]_n (M = Li, Na, K, 2–4) analogous to the alkali CO₂⁻ radical, and two-electron alkali metal reduction affords dianionic clusters of the general formula [M₂(CAAC–CO₂)]_n (5–8) with reduced CO₂ units which are structurally analogous to the carbonite anion CO₂²⁻. It is notable that crystalline clusters of these alkali–CO₂ salts may also be isolated via the “one-pot” reaction of free CO₂ with free CAAC followed by the addition of alkali metals – a process which does not occur in the absence of carbene. Each of the products 2–8 was investigated using a combination of experimental and theoretical methods.

The direct chemical reduction of CAACCO2 adducts by alkali metals to yield multinuclear clusters is reported. The mono- and dianions of CO₂ have been studied for decades and are fundamentally important oxycarbanions and critical species in CO₂ fixation chemistry.     

A window-space-directed assembly strategy for the construction of supertetrahedron-based zeolitic mesoporous metal–organic frameworks with ultramicroporous apertures for selective gas adsorption

Despite their scarcity due to synthetic challenges, supertetrahedron-based metal–organic frameworks (MOFs) possess intriguing architectures, diverse functionalities, and superb properties that make them in-demand materials. Employing a new window-space-directed assembly strategy, a family of mesoporous zeolitic MOFs have been constructed herein from corner-shared supertetrahedra based on homometallic or heterometallic trimers [M₃(OH/O)(COO)₆] (M₃ = Co₃, Ni₃ or Co₂Ti). These MOFs consisted of close-packed truncated octahedral cages possessing a sodalite topology and large β-cavity mesoporous cages (∼22 Å diameter) connected by ultramicroporous apertures (∼5.6 Å diameter). Notably, the supertetrahedron-based sodalite topology MOF combined with the Co₂Ti trimer exhibited high thermal and chemical stability as well as the ability to efficiently separate acetylene (C₂H₂) from carbon dioxide (CO₂).

A series of supertetrahedron (ST)-based sodalite (sod)-topology zeolitic MOFs specimens ST-sod-MOFs featuring ultramicroporous square windows and a mesoporous sodcage have been synthesized via a window-space-directed assembly approach.