Microporous Metal–Organic Frameworks with High Gas Sorption and Separation Capacity

The design, synthesis, and structural characterization of two microporous metal–organic framework structures, [M(bdc)(ted)_0.5]·2 DMF·0.2 H₂O (M = Zn ( 1 ), Cu ( 2 ); H₂bdc = 1,4‐benzenedicarboxylic acid; ted = triethylenediamine; DMF: N,N‐dimethylformamide) is reported. The pore characteristics and gas sorption properties of these compounds are investigated at cryogenic temperatures, room temperature, and higher temperatures by experimentally measuring argon, hydrogen, and selected hydrocarbon adsorption/desorption isotherms. These studies show that both compounds are highly porous with a pore volume of 0.65 ( 1 ) and 0.52 cm³ g^{– 1} ( 2 ). The amount of the hydrogen uptake, 2.1 wt % ( 1 ) and 1.8 wt % ( 2 ) at 77 K (1 atm; 1 atm = 101 325 Pa), places them among the group of metal–organic frameworks (MOFs) having the highest H₂ sorption capacity. [Zn(bdc)(ted)_0.5]·2 DMF·0.2 H₂O adsorbs a very large amount of hydrocarbons, including methanol, ethanol, dimethylether (DME), n‐hexane, cyclohexane, and benzene, giving the highest sorption values among all metal–organic based porous materials reported to date. In addition, these materials hold great promise for gas separation.     

Hydrogen Adsorption in Metal–Organic Frameworks: Cu‐MOFs and Zn‐MOFs Compared

Hydrogen adsorption in two different metal–organic frameworks (MOFs), MOF‐5 and Cu‐BTC (BTC: benzene‐1,3,5‐tricarboxylate), with Zn²⁺ and Cu²⁺ as central metal ions, respectively, is investigated at temperatures ranging from 77 K to room temperature. The process responsible for hydrogen storage in these MOFs is pure physical adsorption with a heat of adsorption of approximately –4 kJ mol^–1. With a saturation value of 5.1 wt.‐% for the hydrogen uptake at high pressures and 77 K, MOF‐5 shows the highest storage capacity ever reported for crystalline microporous materials. However, at low pressures Cu‐BTC shows a higher hydrogen uptake than MOF‐5, making Cu‐based MOFs more promising candidates for potential storage materials. Furthermore, the hydrogen uptake is correlated with the specific surface area for crystalline microporous materials, as shown for MOFs and zeolites.     

Highly Stable Nanoporous Sulfur‐Bridged Covalent Organic Polymers for Carbon Dioxide Removal

Carbon dioxide capture and separation requires robust solids that can stand harsh environments where a hot mixture of gases is often found. Herein, the first and comprehensive syntheses of porous sulfur‐bridged covalent organic polymers (COPs) and their application for carbon dioxide capture in warm conditions and a wide range of pressures (0–200 bar) are reported. These COPs can store up to 3294 mg g^?1 of carbon dioxide at 318 K and 200 bar while being highly stable against heating up to 400 °C. The carbon dioxide capacity of the COPs is also not hindered upon boiling in water for at least one week. Physisorptive binding is prevalent with isosteric heat of adsorptions around 24 kJ mol^?1. M06–2X and RIMP2 calculations yield the same relative trend of binding energies, where, interestingly, the dimer of triazine and benzene play a cooperative role for a stronger binding of CO₂ (19.2 kJ mol^?1) as compared to a separate binding with triazine (13.3 kJ mol^?1) or benzene (11.8 kJ mol^?1).     

In-Plane Heterostructured MoN/MoC Nanosheets with Enhanced Interfacial Charge Transfer for Superior Pseudocapacitive Storage

2D transition metal carbide/nitride heterostructures are emerging pseudocapacitive materials for supercapacitors (SCs); however, the lack of efficient synthesis methods and an in-depth understanding of the pseudocapacitive storage mechanism of these potentially important materials impede their applications in SCs. Herein, 2D MoN/MoC nanosheets with a precisely regulated interface are prepared controllably by a scalable salt-assisted method with bulk MoS₂ as the precursor. In operando infrared spectroscopy and electrochemical quartz crystal microbalance results reveal that the pseudocapacitance of the MoN/MoC nanosheets originates from the reversible reaction between Mo–N sites and H⁺ in the acidic electrolyte. Density-functional theory calculations and X-ray photoelectron spectroscopy disclose that the MoC/MoN heterointerface induces the internal electric field from the accumulated negative charges at the Mo–N sites by electron donation from MoC, leading to enhanced H⁺ adsorption at the Mo–N sites and superior pseudocapacitive storage. The heterostructured MoN/MoC nanosheets show a large volumetric capacity of 1045.3 F cm⁻³ at 1 A cm⁻³, high-rate capability of 702.8 F cm⁻³ at 10 A cm⁻³, and superior cyclability with capacity retention of 98% after 10,000 cycles, which outperform reported Mo-based carbides and nitrides. The results provide new insights into the development of high-performance 2D heterostructured materials for superior pseudocapacitive storage.     

Chemical Blowing Approach for Ultramicroporous Carbon Nitride Frameworks and Their Applications in Gas and Energy Storage

A scalable, template‐free synthetic strategy is presented for the preparation of ultramicroporous carbon nitride frameworks (CNFs) through a chemical blowing approach by using ammonium chloride as blowing agent and hexamethylene tetraamine as the C and N precursor and a subsequent potassium hydroxide chemical activation is employed to obtain CNFs with surface areas up to 1730 m² g^?1 along with a high nitrogen content of 13.3 wt%. CNFs showed CO₂ uptake capacities up to 5.74 mmol g^?1 at 1 bar and 1.67 mmol g^?1 at 0.15 bar, 273 K along with a very high CO₂/N₂ selectivity. In addition, H₂ uptake capacity of 1.9 wt% and the isosteric heats of adsorption (Q _st) value of 9.0 kJ mol^?1 at zero coverage have been also observed. Moreover, the presence of nitrogen‐doped graphene walls in CNFs also facilitated their application as supercapacitors, with capacitance values up to ≈114 F g^?1 at 0.5 A g^?1, along with a good cyclability and capacitance retention. This approach effectively extends unique surface properties of carbon nitrides into the micropore regime for effective capture of small gases and energy storage applications. Importantly, textural properties of CNFs can be simply tuned by judicious choice of organic precursors and the blowing agent.     

Coupling Uniform Pore Size And Multi‑Chemisorption Sites: Hierarchically Ordered Porous Carbon For Ultra-Fast And Large Zinc Ion Storage

Constructing hierarchically ordered macro/meso−microporous structures of carbonaceous cathode with matchable pore size and adequate active sites is significant toward large Zn²⁺ storage, but remains a formidable challenge. Herein, a new perspective is reported for synthesizing phosphorus and nitrogen dual-doped hierarchical ordered porous carbon (PN-HOPC) by eliminating the micropore confinement effect and synchronously introducing multi-chemisorption sites. The interconnected macropore can effectively facilitate long-distance mass transfer, and meso−microporous wall can promote accessibility of active sites. Density functional theory (DFT) calculations identify that the P and N co-doping markedly contributes to the reversible adsorption/desorption of zinc ions and protons. Consequently, the optimized PN-HOPC exhibits outstanding Zn²⁺ storage capabilities in terms of high capacity (211.9 mAh g⁻¹), superb energy density (169.5 Wh kg⁻¹), and ultralong lifespan (99.3% retention after 60 000 cycles). Systematic ex situ measurements integrating with in situ Raman spectroscopy and electrochemical quartz crystal microbalance (EQCM) techniques elucidate that the superior electrochemical capability is ascribed to the synergistic effect of the Zn²⁺, H⁺, and SO₄²⁻ co-adsorption mechanism, as well as invertible chemical adsorption. This study not only provides new insights to design advanced carbon materials toward practical applications but also sheds lights on a deeper understanding of charge storage mechanism for zinc-ion capacitors (ZICs).     

A Quantum‐Chemical Study on Understanding the Dehydrogenation Mechanisms of Metal (Na,K, or Mg) Cation Substitution in Lithium Amide Nanoclusters

The hydrogen‐releasing activity of (LiNH₂)₆–LiH nanoclusters and metal (Na, K, or Mg)‐cation substituted nanoclusters (denoted as (NaNH₂)(LiNH₂)₅, (KNH₂)(LiNH₂)₅, and (MgNH)(LiNH₂)₅) are studied using ab initio molecular orbital theory. Kinetics results show that the rate‐determining step for the dehydrogenation of the (LiNH₂)₆–LiH nanocluster is the ammonia liberation from the amide with a high activation energy of 167.0 kJ mol^?1 (at B3LYP/6‐31 + G(d,p) level). However, metal (Na, K, Mg)‐cation substitution in amide–hydride nanosystems reduces the activation energies for the rate‐determining step to 156.8, 149.6, and 144.1 kJ mol^?1 (at B3LYP/6‐31 + G(d,p) level) for (NaNH₂)(LiNH₂)₅, (KNH₂)(LiNH₂)₅, and (MgNH)(LiNH₂)₅, respectively. Furthermore, only the ?NH₂ group bound to the Na/K cation is destabilized after Na/K cation substitution, indicating that the improving effect from Na/K‐cation substitution is due to a short‐range interaction. On the other hand, Mg‐cation substitution affects all –NH₂ groups in the nanocluster, resulting in weakened N–H covalent bonding together with stronger ionic interactions between Li and the –NH₂ group. The present results shed light on the dehydrogenation mechanisms of metal‐cation substitution in lithium amide–hydride nanoclusters and the application of (MgNH)(LiNH₂)₅ nanoclusters as promising hydrogen‐storage media.     

Structure–Thermodynamic‐Property Relationships in Cyanovinyl‐Based Microporous Polymer Networks for the Future Design of Advanced Carbon Capture Materials

Nitrogen‐rich solid absorbents, which have been immensely tested for carbon dioxide capture, seem until this date to be without decisive molecular engineering or design rules. Here, a family of cyanovinylene‐based microporous polymers synthesized under metal‐catalyzed conditions is reported as a promising candidate for advanced carbon capture materials. These networks reveal that isosteric heats of CO₂ adsorption are directly proportional to the amount of their functional group. Motivated by this finding, polymers produced under base‐catalyzed conditions with tailored quantities of cyanovinyl content confirm the systematical tuning of their sorption enthalpies to reach 40 kJ mol^?1. This value is among the highest reported to date in carbonaceous networks undergoing physisorption. A six‐point‐plot reveals that the structure–thermodynamic‐property relationship is linearly proportional and can thus be perfectly fitted to tailor‐made values prior to experimental measurements. Dynamic simulations show a bowl‐shaped region within which CO₂ is able to sit and interact with its conjugated surrounding, while theoretical calculations confirm the increase of binding sites with the increase of Ph? C?C(CN)? Ph functionality in a network. This concept presents a distinct method for the future design of carbon dioxide capturing materials.     

Toward High‐Performance Capacitive Potassium‐Ion Storage: A Superior Anode Material from Silicon Carbide‐Derived Carbon with a Well‐Developed Pore Structure

Potassium‐ion battery (PIB) using a carbon‐based anode is an ideal device for electrochemical energy storage. However, the large atomic size of potassium ions inevitably leads to huge volume expansion and the collapse of anodes, resulting in the severe capacity fading during the long‐term cycling. Herein, silicon carbide‐derived carbon (SiC‐CDC) with a controllable pore structure is synthesized with a concise etching approach. It exhibits a maximum capacity of 284.8 mA h g^?1 at a current density of 0.1 A g^?1 after 200 cycles as well as a highly reversible capacity of 197.3 mA h g^?1 at a current density of 1.0 A g^?1 even after 1000 cycles. A mixed mechanism of the potassium storage is proposed for this prominent performance. The interconnected pore structure with a high proportion of mesopore volume provides abundant active sites for the adsorption of potassium ions, a shortened electrolyte penetration path, and enlarged accumulation space for potassium ions, eventually leading to facilitated capacitive potassium storage inside this SiC‐CDC electrode. This work provides fundamental theories of designing pore structures for boosting capacitive potassium storage and unveils CDC‐based materials as the prospective anodes for high‐performance PIBs.     

Robust Design of Dual‐Phasic Carbon Cathode for Lithium–Oxygen Batteries

Given that the performance of a lithium–oxygen battery (LOB) is determined by the electrochemical reactions occurring on the cathode, the development of advanced cathode nanoarchitectures is of great importance for the realization of high‐energy‐density, reversible LOBs. Herein, a robust cathode design is proposed for LOBs based on a dual‐phasic carbon nanoarchitecture. The cathode is composed of an interwoven network of porous metal–organic framework (MOF) derived carbon (MOF‐C) and conductive carbon nanotubes (CNTs). The dual‐phasic nanoarchitecture incorporates the advantages of both components: MOF‐C provides a large surface area for the oxygen reactions and a large pore volume for Li₂O₂ storage, and CNTs provide facile pathways for electron and O₂ transport as well as additional void spaces for Li₂O₂ accommodation. It is demonstrated that the synergistic nanoarchitecturing of the dual‐phasic MOF‐C/CNT material results in promising electrochemical performance of LOBs, as evidenced by a high discharge capacity of ≈10 050 mAh g^?1 and a stable cycling performance over 75 cycles.     

Thermochemistry of alloys of transition metals: Part III. Copper-silver, -titanium, -zirconium,and -hafnium at 1373 K

The enthalpies of mixing of liquid copper with liquid silver and with solid titanium, zirconium, and hafnium have been measured by high temperature reaction calorimetry at 1371 to 1373 K. A least squares treatment of the data for copper-silver alloys yields the following expression for the molar enthalpy of mixing: δH_mix = x_Agx_Cu(17.66-5.46 x_Ag) kJ mol^-1. The enthalpies of solution of solid titanium, zirconium, and hafnium in dilute solutions in liquid copper are all exothermic; the following values were found: -2.0 kJ mol^-1 for Ti, -52.5 kJ mol^-1 for Zr, and -46.3 kJ mol^-1 for Hf. These values are all significantly less exothermic than predicted by the semiempirical theory of Miedema. The enthalpies of formation of congruent melting intermetallic phases in the systems Cu-Ti, Cu-Zr, and Cu-Hf were measured by drop calorimetry or by solution calorimetry in liquid copper. The enthalpies of formation of the solid alloys have been compared with corresponding data for the liquid alloys.     

A Highly Efficient Electrochemical Biosensing Platform by Employing Conductive Nanocomposite Entrapping Magnetic Nanoparticles and Oxidase in Mesoporous Carbon Foam

A conductive multi‐catalyst system consisting of Fe₃O₄ magnetic nanoparticles (MNPs) and oxidative enzymes co‐entrapped in the pores of mesoporous carbon is developed as an efficient and robust electrochemical biosensing platform. The construction of the nanocomposite begins with the incorporation of MNPs by impregnating Fe(NO₃)₃ on a wall of mesoporous carbon followed by heat treatment under an Ar/H₂ atmosphere, which results in the formation of magnetic mesoporous carbon (MMC). Glucose oxidase (GOx) is subsequently immobilized in the remaining pore spaces of the MMC by using glutaraldehyde crosslinking to prevent enzyme leaching from the matrix. H₂O₂ generated by the catalytic action of GOx in proportion to the amount of target glucose is subsequently reduced into H₂O by the peroxidase mimetic activity of MNPs generating cathodic current, which can be detected through the conductive carbon matrix. To develop a robust and easy‐to‐use electrocatalytic biosensing platform, a carbon paste electrode is prepared by mechanically mixing the nanocomposite or MMCs and mineral oil. Using this strategy, H₂O₂ and several phenolic compounds are amperometrically determined employing MMCs as peroxidase mimetics, and target glucose was successfully detected over a wide range of 0.5 × 10^?3 to 10 × 10^?3 M , which covers the actual range of glucose concentration in human blood, with excellent storage stability of over two months at room temperature. Sensitivities of the biosensor (19 to 36 nA mM ^?1) are about 7–14 times higher than that of the biosensor using immobilized GOx in mesoporous carbon without MNPs under optimized condition. The biosensor is of considerable interest because of its potential for expansion to any oxidases, which will be beneficial for use in practical applications by replacing unstable organic peroxidase with immobilized MNPs in a conductive carbon matrix.     

Synthesis of MnO2 Nanoparticles Confined in Ordered Mesoporous Carbon Using a Sonochemical Method

A sonochemical method has been successfully used in order to incorporate MnO₂ nanoparticles inside the pore channels of CMK‐3 ordered mesoporous carbon. Modification of the intrachannel surfaces of CMK‐3 to make them hydrophilic enables KMnO₄ to readily penetrate the pore channels. At the same time, the modification changes the surface reactivity, enabling the formation of MnO₂ nanoparticles inside the pores of CMK‐3 by the sonochemical reduction of metal ions. The resultant structures were characterized by X‐ray diffraction (XRD), nitrogen adsorption, and transmission electron microscopy (TEM). CMK‐3 with 20 wt.‐% loading of MnO₂ inside CMK‐3 delivered an improved discharge performance of 223 mA h g^–1 at a relatively high rate of 1 A g^–1. Almost no decrease in specific capacity is observed for the second cycle, and a discharge capacity of more than 165 mA h g^–1 is retained after 100 cycles. This is attributed to the nanometer‐sized MnO₂ formed inside CMK‐3 and the high surface area of the mesopores (3.1 nm) in which the MnO₂ nanoparticles are formed.     

Interfacial Engineering Promoting Electrosynthesis of Ammonia over Mo/Phosphotungstic Acid with High Performance

Electrochemical nitrogen reduction reaction (eNRR) is recognized as a promising approach for ammonia synthesis, which is, however, impeded by the inert nitrogen and the unavoidable competing hydrogen evolution reaction (HER). Here, a Mo-PTA@CNT electrocatalyst in which Mo species are anchored on the fourfold hollow sites of phosphotungstic acid (PTA) and closely embedded in multi-walled carbon nanotubes (CNT) for immobilization is designed and synthesized. Interestingly, the catalyst presents a high ammonia yield rate of 51 ± 1 µg h⁻¹ mg_cat.⁻¹ and an excellent Faradaic efficiency of 83 ± 1% at −0.1 V versus RHE under ambient conditions. The concentrations of NH₄⁺ are also quantitatively calculated by ¹H NMR spectra and ion chromatography. Isotopic labeling identifies that the N atom of the formed NH₃ originates from N₂. The controlled experiments confirm a strong interaction between Mo-PTA and N₂ with an adsorption energy of 50.46 kJ mol⁻¹ and activation energy of 21.36 kJ mol⁻¹. More importantly, due to CNT's gas storage and hydrophobicity properties, there is a fourfold increase in N₂ content. The concentration of H₂O is reduced by more than half at the interface of the electrode. Thus, the activity of eNRR can be significantly improved with ultrahigh electron selectivity.     

Order Mesoporous Carbon Spheres with Precise Tunable Large Pore Size by Encapsulated Self‐Activation Strategy

Order mesoporous carbon spheres (O‐MCS) have wide applications in catalysis, absorption, and energy storage/conversion due to their ordered mesoporous channels, large surface areas, and quantum effects in the nanoscale. However, realizing a precise control of large mesoporous size still remains a big challenge. Herein, an encapsulated self‐activation strategy to prepare highly ordered mesoporous carbon spheres with precise tunable large pore sizes is first reported. The large mesopore size is achieved by encapsulating mesoporous polymer sphere in compact silica shell for pyrolysis process. Moreover, the self‐activation mechanism endows the O‐MCS high surface area, large mesoporous size, and pore volume. In addition, simply increasing the amount of silica precursor will enlarge the pore sizes of O‐MCS from 3.1 to 10.0 nm with increased specific surface area from 696 to 1186 m² g^?1. The large order mesoporous structure of O‐MCS, which can facilitate diffusion of guest molecules in the channels exhibit great advantage in the adsorption and electrochemical applications.     

Formation of Chiral Mesopores in Conducting Polymers by Chiral‐Lipid‐Ribbon Templating and “Seeding” Route

Conducting polymer nanofibers with controllable chiral mesopores in the size, the shape, and handedness have been synthesized by chiral lipid ribbon templating and “seeding” route. Chiral mesoporous conducting poly(pyrrole) (CMPP) synthesized with very small amount of chiral amphiphilic molecules (usually < 3%) has helically twisted channels with well‐defined controllable pore size of 5–20 nm in central axis of the twisted fibers. The structure and chirality of helical mesopores have been characterized by high‐resolution transmission electron microscope (HRTEM), scanning electron microscope (SEM) and electron tomography. The average pore diameters of chiral mesopores were approximately estimated from the N₂ adsorption–desorption data and calculated by the conversion calculation from helical ribbons to a rectangular straight tape. The pore size of CMPP has been controlled by choosing different alkyl chain lengths of chiral lipid molecules or precisely adjusting the H₂O/EtOH volume ratio.     

Oxidation of Fe (II) in sulfuric acid solutions with dissolved molecular oxygen

The oxidation of Fe(II) with dissolved molecular oxygen was studied in sulfuric acid solutions containing 0.2 mol . dm^-3 FeSO₄ at temperatures ranging from 343 to 363 K. In solutions of sulfuric acid above 0.4 mol . dm^-3, the oxidation of Fe (II) was found to proceed through two parallel paths. In one path the reaction rate was proportional to both [Fe²⁺]² and po₂, exhibiting an activation energy of 51.6 . kJ mol^-1. In another path the reaction rate was proportional to [Fe²⁺]², [SO_4-], and po₂ with an activation energy of 144.6 kJ . mol^-1. A reaction mechanism in which the SO_4- ions play an important role was proposed for the oxidation of Fe(II). In dilute solutions of sulfuric acid below 0.4 mol . dm^-3, the rate of the oxidation reaction was found to be proportional to both [Fe(II)]² and Po₂, and was also affected by [H⁺] and [SO_2- ⁴]. The decrease in [H⁺] resulted in the increase of reaction rate. The discussion was further extended to the effect of Fe (III) on the oxidation reaction of Fe (II).     

High‐Content,Well‐Dispersed γ‐Fe2O3 Nanoparticles Encapsulated in Macroporous Silica with Superior Arsenic Removal Performance

Novel composites of iron oxide encapsulated in macroporous silica with excellent arsenic adsorption performance have been successfully developed. Macroporous silica foams with large pore sizes of ≈100 nm and a high pore volume of 1.6 cm³ g^?1 are chosen as the porous matrix. Electron tomography technique confirms that γ‐Fe₂O₃ nanoparticles with an average particle size of ≈6 nm are spatially well‐dispersed and anchored on the pore walls at even a high γ‐Fe₂O₃ content of 34.8 wt%, rather than forming aggregates inside the pores or on the external surface. The open large‐pore structure, high loading amount, and the non‐aggregated nature of γ‐Fe₂O₃ nanoparticles lead to increased adsorption sites and thus high adsorption capacities of both As (V) and As (III) without pre‐treatment (248 and 320 mg g^?1, respectively). Moreover, the composites can reduce the concentration of both As (V) and As (III) from 100 to 2 μg L^?1. It is also demonstrated that the composites can be applied in a household drinking water treatment device, which can continuously treat 20 L of wastewater containing As (V) with the effluent concentration lower than the World Health Organization standard.     

Construction of Tri-Functional HOFs Material for Efficient Selective Adsorption and Photodegradation of Bisphenol A and Hydrogen Production

This study proposes the construction of porous nanomaterial (HOFs@Fe³⁺) which anchors non-noble metal ions Fe³⁺ onto nanoscale rod-like hydrogen-bonded organic frameworks (HOFs) by electrostatic and coordination interactions. The high specific surface area and the abundance of hydrogen-bond adsorption active sites in pore structure of HOFs@Fe³⁺ facilitate strong interactions with the double  OH in bisphenol A (BPA), resulting in the highest saturation adsorption of BPA that has been reported so far (452 mg g^-1). In addition, the ordered conjugate stacking framework structure and hydrogen bond of HOFs@Fe³⁺ and the variable valence properties of Fe³⁺ create new pathways for efficient separation of photogenerated carriers. The results show that HOFs@Fe³⁺ can completely adsorb and photodegrade 50 ppm BPA within 20 min, owing to the abundant hydrogen bond that acts both as adsorption sites to accelerate the mass transfer process and as catalytic sites to ensure adsorption and photodegradation can be matched synergistically. Meanwhile, the efficiency of photocatalytic H₂ production by HOFs@Fe³⁺ reaches 21.55 mmol g^-1 h^-1 with non-noble metal Fe³⁺ as co-catalyst. This tri-functional material with high adsorption capacity, high photodegradation efficiency, and high photocatalytic H₂ production activity can be successfully used to solve the long-standing conflict between environment and energy.     

A New Approach to Tuning Carbon Ultramicropore Size at Sub‐Angstrom Level for Maximizing Specific Capacitance and CO2 Uptake

Ultramicroporous carbon materials with uniform pore size accurately adjusted to the dimension of electrolyte ions or CO₂ molecule are highly desirable for maximizing specific capacitance and CO₂ uptake. However, efficient ways to fine‐tuning ultramicropore size at angstrom level are scarce. A completely new approach to precisely tuning carbon ultramicropore size at sub‐angstrom level is proposed herein. Due to the varying activating strength and size of the alkali ions, the ultramicropore size can be finely tuned in the range of 0.60–0.76 nm as the activation ion varies from Li⁺ to Cs⁺. The carbons prepared by direct pyrolysis of alkali salts of carboxylic phenolic resins yield ultrahigh capacitances of up to 223 F g^‐1 (205 F cm^‐3) in ionic liquid electrolyte, and superior CO₂ uptake of 5.20 mmol g^‐1 at 1.0 bar and 25 °C. Such outstanding performance of the finely tuned carbons lies in its adjustable pore size perfectly adapted to the electrolyte ions and CO₂ molecule. This work paves the way for a new route to finely tuning ultramicropore size at the sub‐angstrom level in carbon materials.