A Robust 3D Cage‐like Ultramicroporous Network Structure with High Gas‐Uptake Capacity

A three‐dimensional (3D) cage‐like organic network (3D‐CON) structure synthesized by the straightforward condensation of building blocks designed with gas adsorption properties is presented. The 3D‐CON can be prepared using an easy but powerful route, which is essential for commercial scale‐up. The resulting fused aromatic 3D‐CON exhibited a high Brunauer–Emmett–Teller (BET) specific surface area of up to 2247 m² g^?1. More importantly, the 3D‐CON displayed outstanding low pressure hydrogen (H₂, 2.64 wt %, 1.0 bar and 77 K), methane (CH₄, 2.4 wt %, 1.0 bar and 273 K), and carbon dioxide (CO₂, 26.7 wt %, 1.0 bar and 273 K) uptake with a high isosteric heat of adsorption (H₂, 8.10 kJ mol^?1; CH₄, 18.72 kJ mol^?1; CO₂, 31.87 kJ mol^?1). These values are among the best reported for organic networks with high thermal stability (ca. 600 °C).     

Catholyte‐Free Electrocatalytic CO2 Reduction to Formate

Electrochemical reduction of carbon dioxide (CO₂) into value‐added chemicals is a promising strategy to reduce CO₂ emission and mitigate climate change. One of the most serious problems in electrocatalytic CO₂ reduction (CO₂R) is the low solubility of CO₂ in an aqueous electrolyte, which significantly limits the cathodic reaction rate. This paper proposes a facile method of catholyte‐free electrocatalytic CO₂ reduction to avoid the solubility limitation using commercial tin nanoparticles as a cathode catalyst. Interestingly, as the reaction temperature rises from 303 K to 363 K, the partial current density (PCD) of formate improves more than two times with 52.9 mA cm^?2, despite the decrease in CO₂ solubility. Furthermore, a significantly high formate concentration of 41.5 g L^?1 is obtained as a one‐path product at 343 K with high PCD (51.7 mA cm^?2) and high Faradaic efficiency (93.3 %) via continuous operation in a full flow cell at a low cell voltage of 2.2 V.     

Metal Microporous Aromatic Polymers with Improved Performance for Small Gas Storage

A novel metal‐doping strategy was developed for the construction of iron‐decorated microporous aromatic polymers with high small‐gas‐uptake capacities. Cost‐effective ferrocene‐functionalized microporous aromatic polymers (FMAPs) were constructed by a one‐step Friedel–Crafts reaction of ferrocene and s‐triazine monomers. The introduction of ferrocene endows the microporous polymers with a regular and homogenous dispersion of iron, which avoids the slow reunion that is usually encountered in previously reported metal‐doping procedures, permitting a strong interaction between the porous solid and guest gases. Compared to ferrocene‐free analogues, FMAP‐1, which has a moderate BET surface area, shows good gas‐adsorption capabilities for H₂ (1.75 wt % at 77 K/1.0 bar), CH₄ (5.5 wt % at 298 K/25.0 bar), and CO₂ (16.9 wt % at 273 K/1.0 bar), as well as a remarkably high ideal adsorbed solution theory CO₂/N₂ selectivity (107 v/v at 273 K/(0–1.0) bar), and high isosteric heats of adsorption of H₂ (16.9 kJ mol^?1) and CO₂ (41.6 kJ mol^?1).     

A Strategy for Constructing Pore-Space-Partitioned MOFs with High Uptake Capacity for C2 Hydrocarbons and CO2

Introduction of pore partition agents into hexagonal channels of MIL-88 type (acs topology) endows materials with high tunability in gas sorption. Here, we report a strategy to partition acs framework into pacs (partitioned acs) crystalline porous materials (CPM). This strategy is based on insertion of in situ synthesized 4,4′-dipyridylsulfide (dps) ligands. One third of open metal sites in the acs net are retained in pacs MOFs; two thirds are used for pore-space partition. The Co₂V-pacs MOFs exhibit near or at record high uptake capacities for C₂H₂, C₂H₄, C₂H₆, and CO₂ among MOFs. The storage capacity of C₂H₂ is 234 cm³ g⁻¹ (298 K) and 330 cm³ g⁻¹ (273 K) at 1 atm for CPM-733-dps (the Co₂V-BDC form, BDC=1,4-benzenedicarboxylate). These high uptake capacities are accomplished with low heat of adsorption, a feature desirable for low-energy-cost adsorbent regeneration. CPM-733-dps is stable and shows no loss of C₂H₂ adsorption capacity following multiple adsorption–desorption cycles.     

Water‐Stable Zirconium‐Based Metal–Organic Framework Material with High‐Surface Area and Gas‐Storage Capacities

We designed, synthesized, and characterized a new Zr‐based metal–organic framework material, NU‐1100 , with a pore volume of 1.53 ccg^?1 and Brunauer–Emmett–Teller (BET) surface area of 4020 m²g^?1; to our knowledge, currently the highest published for Zr‐based MOFs. CH₄/CO₂/H₂ adsorption isotherms were obtained over a broad range of pressures and temperatures and are in excellent agreement with the computational predictions. The total hydrogen adsorption at 65 bar and 77 K is 0.092 g g^?1, which corresponds to 43 g L^?1. The volumetric and gravimetric methane‐storage capacities at 65 bar and 298 K are approximately 180 v_STP/v and 0.27 g g^?1, respectively.     

Microporous La–Metal–Organic Framework (MOF) with Large Surface Area

A microporous La–metal‐organic framework (MOF) has been synthesized by the reaction of La(NO₃)₃ ? 6 H₂O with a ligand 4,4′,4′′‐s‐triazine‐1,3,5‐triyltri‐p‐aminobenzoate (TATAB) featuring three carboxylate groups. Crystal structure analysis confirms the formation of 3D MOF with hexagonal micropores, a Brunauer–Emmett—Teller (BET) surface area of 1074 m² g^?1 and high thermal and chemical stability. The CO₂ adsorption capacities are 76.8 cm³ g^?1 at 273 K and 34.6 cm³ g^?1 at 293 K, a highest measured CO₂ uptake for a Ln–MOFs.     

Water‐stable Adenine‐based MOFs with Polar Pores for Selective CO2 Capture

Here, we report two novel water‐stable amine‐functionalized MOFs, namely IISERP‐MOF26 ([NH₂(CH₃)₂][Cu₂O(Ad)(BDC)]?(H₂O)₂(DMA), 1 ) and IISERP‐MOF27 ([NH₂(CH₃)₂]_1/2[Zn₄O(Ad)₃(BDC)₂]?(H₂O)₂(DMF)_1/2, 2 ), which show selective CO₂ capture capabilities. They are made by combining inexpensive and readily available terephthalic acid and N‐rich adenine with Cu and Zn, respectively. They possess 1D channels decorated by the free amine group from the adenine and the polarizing oxygen atoms from the terephthalate units. Even more, there are dimethyl ammonium (DMA⁺) cations in the pore rendering an electrostatic environment within the channels. The activated Cu‐ and Zn‐MOFs physisorb about 2.7 and 2.2 mmol g^?1 of CO₂, respectively, with high CO₂/N₂ and moderate CO₂/CH₄ selectivity. The calculated heat of adsorption (HOA=21–23 kJ mol^?1) for the CO₂ in both MOFs suggest optimal physical interactions which corroborate well with their facile on‐off cycling of CO₂. Notably, both MOFs retain their crystallinity and porosity even after soaking in water for 24 hours as well as upon exposure to steam over 24 hours. The exceptional thermal and chemical stability, favorable CO₂ uptakes and selectivity and low HOA make these MOFs promising sorbents for selective CO₂ capture applications. However, the MOF′s low heat of adsorption despite having a highly CO₂‐loving groups lined walls is quite intriguing.     

3D Hexagonal Mesoporous Silica and Its Organic Functionalization for High CO2 Uptake

Highly ordered 3D‐hexagonal mesoporous silica HMS‐3 and its vinyl‐ and 3‐chloropropyl‐functionalized analogues HMS‐4 and ‐5, respectively, are synthesized under strongly alkaline conditions at 277 K. Tetraethyl orthosilicate, vinyltrimethoxysilane, and 3‐chloropropyltrimethoxysilane are used as silica sources, and cetyltrimethylammonium bromide as the structure‐directing agent. The 3D‐hexagonal pore structures of HMS‐3, 4‐, and ‐5 were confirmed by powder XRD and high‐resolution TEM studies. Brunauer–Emmett–Teller surface areas of these materials are 1353, 1211, and 603 m² g^?1 for HMS‐3, ‐4, and ‐5, respectively. Among these materials, vinyl‐functionalized mesoporous material HMS‐4 adsorbs the highest CO₂ (5.5 mmol g^?1, 24.3 wt %) under 3 bar pressure at 273 K. The 3D‐hexagonal pore openings, very high surface area, and cagelike mesopores as well as organic functionalization could be responsible for very high CO₂ uptakes of these materials compared to other related mesoporous silica‐based materials.     

Microporous Polymers from a Carbazole‐Based Triptycene Monomer: Synthesis and Their Applications for Gas Uptake

Two kinds of novel organic microporous polymers TCP s ( TCP‐A and TCP‐B ) were prepared by two cost‐effective synthetic strategies from the monomer of tricarbazolyltriptycene ( TCT ). Their structure and properties were characterized by FT‐IR, solid ¹³C NMR, powder XRD, SEM, TEM, and gas absorption measurements. TCP‐B displayed a high surface area (1469 m² g^?1) and excellent H₂ storage (1.70 wt % at 1 bar/77 K) and CO₂ uptake abilities (16.1 wt % at 1 bar/273 K), which makes it a promising material for potential application in gas storage.     

No More HF: Teflon‐Assisted Ultrafast Removal of Silica to Generate High‐Surface‐Area Mesostructured Carbon for Enhanced CO2 Capture and Supercapacitor Performance

An innovative technique to obtain high‐surface‐area mesostructured carbon (2545 m² g^?1) with significant microporosity uses Teflon as the silica template removal agent. This method not only shortens synthesis time by combining silica removal and carbonization in a single step, but also assists in ultrafast removal of the template (in 10 min) with complete elimination of toxic HF usage. The obtained carbon material (JNC‐1) displays excellent CO₂ capture ability (ca. 26.2 wt % at 0 °C under 0.88 bar CO₂ pressure), which is twice that of CMK‐3 obtained by the HF etching method (13.0 wt %). JNC‐1 demonstrated higher H₂ adsorption capacity (2.8 wt %) compared to CMK‐3 (1.2 wt %) at ?196 °C under 1.0 bar H₂ pressure. The bimodal pore architecture of JNC‐1 led to superior supercapacitor performance, with a specific capacitance of 292 F g^?1 and 182 F g^?1 at a drain rate of 1 A g^?1 and 50 A g^?1, respectively, in 1 m H₂SO₄ compared to CMK‐3 and activated carbon.     

Framework Cationization by Preemptive Coordination of Open Metal Sites for Anion‐Exchange Encapsulation of Nucleotides and Coenzymes

Cationic frameworks can selectively trap anions through ion exchange, and have applications in ion chromatography and drug delivery. However, cationic frameworks are much rarer than anionic or neutral ones. Herein, we propose a concept, preemptive coordination (PC), for targeting positively charged metal–organic frameworks (P‐MOFs). PC refers to proactive blocking of metal coordination sites to preclude their occupation by neutralizing ligands such as OH^?. We use 20 MOFs to show that this PC concept is an effective approach for developing P‐MOFs whose high stability, porosity, and anion‐exchange capability allow immobilization of anionic nucleotides and coenzymes, in addition to charge‐ and size‐selective capture or separation of organic dyes. The CO₂ and C₂H₂ uptake capacity of 117.9 cm³ g^?1 and 148.5 cm³ g^?1, respectively, at 273 K and 1 atm, is exceptionally high among cationic framework materials.     

Tuning CO2 Uptake and Reversible Iodine Adsorption in Two Isoreticular MOFs through Ligand Functionalization

The synthesis and characterization of two isoreticular metal–organic frameworks (MOFs), {[Cd(bdc)(4‐bpmh)]}_n?2 n(H₂O) ( 1 ) and {[Cd(2‐NH₂bdc)(4‐bpmh)]}_n?2 n(H₂O) ( 2 ) [bdc=benzene dicarboxylic acid; 2‐NH₂bdc=2‐amino benzene dicarboxylic acid; 4‐bpmh=N,N‐bis‐pyridin‐4‐ylmethylene‐hydrazine], are reported. Both compounds possess similar two‐fold interpenetrated 3D frameworks bridged by dicarboxylates and a 4‐bpmh linker. The 2D Cd‐dicarboxylate layers are extended along the a‐axis to form distorted square grids which are further pillared by 4‐bpmh linkers to result in a 3D pillared‐bilayer interpenetrated framework. Gas adsorption studies demonstrate that the amino‐functionalized MOF 2 shows high selectivity for CO₂ (8.4 wt % 273 K and 7.0 wt % 298 K) over CH₄, and the uptake amounts are almost double that of non‐functional MOF 1 . Iodine (I₂) adsorption studies reveal that amino‐functionalized MOF 2 exhibits a faster I₂ adsorption rate and controlled delivery of I₂ over the non‐functionalized homolog 1 .     

Analysis of High and Selective Uptake of CO2 in an Oxamide‐Containing {Cu2(OOCR)4}‐Based Metal–Organic Framework

The porous framework [Cu₂(H₂O)₂L] ? 4 H₂O ? 2 DMA (H₄L=oxalylbis(azanediyl)diisophthalic acid; DMA=N,N‐dimethylacetamide), denoted NOTT‐125, is formed by connection of {Cu₂(RCOO)₄} paddlewheels with the isophthalate linkers in L^4?. A single crystal structure determination reveals that NOTT‐125 crystallises in monoclinic unit cell with a=27.9161(6), b=18.6627(4) and c=32.3643(8) Å, β=112.655(3)°, space group P2₁/c. The structure of this material shows fof topology, which can be viewed as the packing of two types of cages (cage A and cage B) in three‐dimensional space. Cage A is constructed from twelve {Cu₂(OOCR)₄} paddlewheels and six linkers to form an ellipsoid‐shaped cavity approximately 24.0 Å along its long axis and 9.6 Å across its central diameter. Cage B consists of six {Cu₂(OOCR)₄} units and twelve linkers and has a spherical diameter of 12.7 Å taking into account the van der Waals radii of the atoms. NOTT‐125 incorporates oxamide functionality within the pore walls, and this, combined with high porosity in desolvated NOTT‐125a, is responsible for excellent CO₂ uptake (40.1 wt % at 273 K and 1 bar) and selectivity for CO₂ over CH₄ or N₂. Grand canonical Monte Carlo (GCMC) simulations show excellent agreement with the experimental gas isotherm data, and a computational study of the specific interactions and binding energies of both CO₂ and CH₄ with the linkers in NOTT‐125 reveals a set of strong interactions between CO₂ and the oxamide motif that are not possible with a single amide.     

Calorimetric study of the CO2 adsorption on carbon materials

Given the great interest in the CO₂ removal and decreasing their impact on the environment, in this work, a calorimetric study of CO₂ adsorption on different activated carbons was performed. For this purpose, we used two methodologies for the determination heat of CO₂ adsorption: determination of CO₂ isotherms at different temperatures and adsorption calorimetry. The heats determined by these two techniques were compared. In this regard, carbonaceous materials of granular and monolithic types were prepared, characterized, and functionalized for carbon dioxide adsorption. As precursor material, African palm stones that were activated with H₃PO₄ and CaCl₂ at different concentrations was used. The obtained materials were functionalized in gas phase with NH₃ and liquid phase with NH₄OH, with the intention to incorporate the surface basic groups (amines or nitrogen groups) and subsequently were studied for CO₂ adsorption at 273 K and atmospheric pressure. For characterization of these materials, the following techniques are used: N₂ adsorption at 77 K and immersion calorimetry in different solvents. The experimental results show the obtaining of micropores and mesoporous (moderately) materials, with surface area between 430 and 1,425 m² g^?1 and pore volumes between 0.17 and 0.53 cm³ g^?1. It was determined that there is a difference between the heats of CO₂ adsorption obtained by the techniques employed. This deviation between the values corresponds to the methodological difference between the two experiments. In this work, we obtained a maximum adsorption capacity of CO₂, which is greater than 334 mg CO₂ g^?1 at 273 K and 1 bar in carbon materials with moderate surface area and pores volume.     

Highly Efficient Conversion of Propargylic Amines and CO2 Catalyzed by Noble‐Metal‐Free [Zn116] Nanocages

The reaction of propargylic amines and CO₂ can provide high‐value‐added chemical products. However, most of catalysts in such reactions employ noble metals to obtain high yield, and it is important to seek eco‐friendly noble‐metal‐free MOFs catalysts. Here, a giant and lantern‐like [Zn₁₁₆] nanocage in zinc‐tetrazole 3D framework [Zn₂₂(Trz)₈(OH)₁₂(H₂O)₉?8 H₂O]_n Trz=(C₄N₁₂O)^4? ( 1 ) was obtained and structurally characterized. It consists of six [Zn₁₄O₂₁] clusters and eight [Zn₄O₄] clusters. To our knowledge, this is the highest‐nuclearity nanocages constructed by Zn‐clusters as building blocks to date. Importantly, catalytic investigations reveal that 1 can efficiently catalyze the cycloaddition of propargylic amines with CO₂, exclusively affording various 2‐oxazolidinones under mild conditions. It is the first eco‐friendly noble‐metal‐free MOFs catalyst for the cyclization of propargylic amines with CO₂. DFT calculations uncover that Zn^II ions can efficiently activate both C≡C bonds of propargylic amines and CO₂ by coordination interaction. NMR and FTIR spectroscopy further prove that Zn‐clusters play an important role in activating C≡C bonds of propargylic amines. Furthermore, the electronic properties of related reactants, intermediates and products can help to understand the basic reaction mechanism and crucial role of catalyst 1 .     

Lithium‐Functionalized Metal–Organic Frameworks that Show >10 wt % H2 Uptake at Ambient Temperature

We have used grand canonical Monte Carlo simulations with a first‐principles‐based force field to show that metal–organic frameworks (MOFs) with Li functional groups (i.e. C? Li bonds) allow for exceptional H₂ uptake at ambient temperature. For example, at 298 K and 100 bar, IRMOF‐1‐4Li shows a total H₂ uptake of 5.54 wt % and MOF‐200‐27Li exhibits a total H₂ uptake of 10.30 wt %, which are much higher than the corresponding values with pristine MOFs. Li‐functionalized MOF‐200 (MOF‐200‐27Li) shows 11.84 wt % H₂ binding at 243 K and 100 bar. These hydrogen‐storage capacities exceed the 2015 DOE target of 5.5 wt % H₂. Moreover, the incorporation of Li functional groups into MOFs provides more benefits, such as higher delivery amount, for H₂ uptake than previously reported Li‐doped MOFs.     

Three novel topologically different metal–organic frameworks built from 3‐nitro‐4‐(pyridin‐4‐yl)benzoic acid

The design and synthesis of metal–organic frameworks (MOFs) have attracted much interest due to the intriguing diversity of their architectures and topologies. However, building MOFs with different topological structures from the same ligand is still a challenge. Using 3‐nitro‐4‐(pyridin‐4‐yl)benzoic acid (HL) as a new ligand, three novel MOFs, namely poly[[(N,N‐dimethylformamide‐κO)bis[μ₂‐3‐nitro‐4‐(pyridin‐4‐yl)benzoato‐κ³O,O′:N]cadmium(II)] N,N‐dimethylformamide monosolvate methanol monosolvate], {[Cd(C₁₂H₇N₂O₄)₂(C₃H₇NO)]·C₃H₇NO·CH₃OH}_n, ( 1 ), poly[[(μ₂‐acetato‐κ²O:O′)[μ₃‐3‐nitro‐4‐(pyridin‐4‐yl)benzoato‐κ³O:O′:N]bis[μ₃‐3‐nitro‐4‐(pyridin‐4‐yl)benzoato‐κ⁴O,O′:O′:N]dicadmium(II)] N,N‐dimethylacetamide disolvate monohydrate], {[Cd₂(C₁₂H₇N₂O₄)₃(CH₃CO₂)]·2C₄H₉NO·H₂O}_n, ( 2 ), and catena‐poly[[[diaquanickel(II)]‐bis[μ₂‐3‐nitro‐4‐(pyridin‐4‐yl)benzoato‐κ²O:N]] N,N‐dimethylacetamide disolvate], {[Ni(C₁₂H₇N₂O₄)₂(H₂O)₂]·2C₄H₉NO}_n, ( 3 ), have been prepared. Single‐crystal structure analysis shows that the Cd^II atom in MOF ( 1 ) has a distorted pentagonal bipyramidal [CdN₂O₅] coordination geometry. The [CdN₂O₅] units as 4‐connected nodes are interconnected by L^? ligands to form a fourfold interpenetrating three‐dimensional (3D) framework with a dia topology. In MOF ( 2 ), there are two crystallographically different Cd^II ions showing a distorted pentagonal bipyramidal [CdNO₆] and a distorted octahedral [CdN₂O₄] coordination geometry, respectively. Two Cd^II ions are connected by three carboxylate groups to form a binuclear [Cd₂(COO)₃] cluster. Each binuclear cluster as a 6‐connected node is further linked by acetate groups and L^? ligands to produce a non‐interpenetrating 3D framework with a pcu topology. MOF ( 3 ) contains two crystallographically distinct Ni^II ions on special positions. Each Ni^II ion adopts an elongated octahedral [NiN₂O₄] geometry. Each Ni^II ion as a 4‐connected node is linked by L^? ligands to generate a two‐dimensional network with an sql topology, which is further stabilized by two types of intermolecular OW—HW…O hydrogen bonds to form a 3D supramolecular framework. MOFs ( 1 )–( 3 ) were also characterized by powder X‐ray diffraction, IR spectroscopy and thermogravimetic analysis. Furthermore, the solid‐state photoluminescence of HL and MOFs ( 1 ) and ( 2 ) have been investigated. The photoluminescence of MOFs ( 1 ) and ( 2 ) are enhanced and red‐shifted with respect to free HL. The gas adsorption investigation of MOF ( 2 ) indicates a good separation selectivity (71) of CO₂/N₂ at 273 K (i.e. the amount of CO₂ adsorption is 71 times higher than N₂ at the same pressure).     

Mixed Metal–Organic Framework with Multiple Binding Sites for Efficient C2H2/CO2 Separation

The separation of C₂H₂/CO₂ is particularly challenging owing to their similarities in physical properties and molecular sizes. Reported here is a mixed metal–organic framework (M′MOF), [Fe(pyz)Ni(CN)₄] ( FeNi‐M′MOF , pyz=pyrazine), with multiple functional sites and compact one‐dimensional channels of about 4.0 Å for C₂H₂/CO₂ separation. This MOF shows not only a remarkable volumetric C₂H₂ uptake of 133 cm³ cm^?3, but also an excellent C₂H₂/CO₂ selectivity of 24 under ambient conditions, resulting in the second highest C₂H₂‐capture amount of 4.54 mol L^?1, thus outperforming most previous benchmark materials. The separation performance of this material is driven by π–π stacking and multiple intermolecular interactions between C₂H₂ molecules and the binding sites of FeNi‐M′MOF . This material can be facilely synthesized at room temperature and is water stable, highlighting FeNi‐M′MOF as a promising material for C₂H₂/CO₂ separation.     

A Polyhedron‐based Metal‐Organic Framework showing high CO2 Adsorption Capacity

A novel porous copper‐based metal‐organic framework {[Cu₂(TTDA)₂]*(DMA)₇}_n ( 1 ) (DMA = N,N‐dimethylacetamide) was designed and synthesized via the combination of a dual‐functional organic linker 5′‐(4‐(4H‐1,2,4‐triazol‐4‐yl)phenyl)‐[1,1′:3′,1′′‐terphenyl]‐4,4′′‐dicarboxylic acid (H₂TTDA) and a dinuclear Cu^II paddle‐wheel cluster. This MOF is characterized by elemental analysis, powder X‐ray diffraction (PXRD), thermo gravimetric analysis (TGA), and single‐crystal X‐ray diffraction. The framework is constructed from two types of cages (octahedral and cuboctahedral cages) and exhibits two types of circular‐shaped channels of approximate size of 5.8 and 11.4 Å along the crystallographic c axis. The gas sorption experiments indicate that it possesses a large surface area (1687 m² · g^–1) and high CO₂ adsorption capacities around room temperature (up to 172 cm³ · g^–1 at 273 K and 124 cm³ · g^–1 at 298 K).     

Ultramicroporous Building Units as a Path to Bi‐microporous Metal–Organic Frameworks with High Acetylene Storage and Separation Performance

A strategy called ultramicroporous building unit (UBU) is introduced. It allows the creation of hierarchical bi‐porous features that work in tandem to enhance gas uptake capacity and separation. Smaller pores from UBUs promote selectivity, while larger inter‐UBU packing pores increase uptake capacity. The effectiveness of this UBU strategy is shown with a cobalt MOF (denoted SNNU‐45) in which octahedral cages with 4.5 Å pore size serve as UBUs. The C₂H₂ uptake capacity at 1 atm reaches 193.0 cm³ g^?1 (8.6 mmol g^?1) at 273 K and 134.0 cm³ g^?1 (6.0 mmol g^?1) at 298 K. Such high uptake capacity is accompanied by a high C₂H₂/CO₂ selectivity of up to 8.5 at 298 K. Dynamic breakthrough studies at room temperature and 1 atm show a C₂H₂/CO₂ breakthrough time up to 79 min g^?1, among top‐performing MOFs. Grand canonical Monte Carlo simulations agree that ultrahigh C₂H₂/CO₂ selectivity is mainly from UBU ultramicropores, while packing pores promote C₂H₂ uptake capacity.