High Heat Of Adsorption Research Articles

Hierarchically porous carbon foams coated with carbon nitride: Insights into adsorbents for pre-combustion and post-combustion CO2 separation

Adsorption is fundamental to many industrial processes, including separation of carbon dioxide from other gases in pre- or post-combustion gas mixtures. Adsorbents should have high capacity and selectivity, which are both intimately linked with surface area, pore size distribution, and surface energy. Porous carbons are cheap and scalable adsorbents, but greater understanding of how their textural properties and surface chemistry affects their performance is needed. Here, we investigate the effect of nitrogen doping on CO2 adsorption. Microporous carbon foams with large surface area (>2500 m2 g−1) and pore volume (1.6 cm3 g−1) are synthesized, then coated with varying amounts of carbon nitride (up to 17 at% nitrogen) to achieve high CO2 uptake (25.5 mmol g−1) and selectivity (CO2:N2 = 21), whilst also giving insights into the relationship between structure and function. At low pressure (relevant to post-combustion capture), moderate carbon nitride loading leads to enhanced uptake and selectivity by combining large ultramicropore volume with the introduction of Lewis base sites, leading to high isosteric heat of adsorption. Higher carbon nitride loading further increases selectivity but lowers uptake by blocking micropores. Conversely, at high pressure (relevant to pre-combustion capture) the uncoated carbon foam displays superior uptake, because mesoporosity is the dominant factor in this regime, rather than the presence of ultramicropores. Finally, the samples displayed excellent regeneration under repeated adsorption–desorption cycles, and breakthrough curves were measured. These results underscore the delicate balance required for optimal material design when applying porous carbon adsorbents to CO2 separation processes. Moving forward, improved adsorbents will contribute to the proliferation of carbon capture and storage (CCS) and carbon capture and utilisation (CCU) technologies, ultimately contributing reduced anthropogenic CO2 emissions.

Efficient CO2 removal enabled by N, S co-doped hierarchical porous carbon derived from sustainable lignin

Biomass-derived heteroatoms-doped hierarchical porous carbon materials are highly regarded as promising CO2 adsorbents. However, these materials cannot simultaneously exhibit advanced porosity, high yield, and high heteroatom content. Herein, a series of N, S co-doped hierarchical porous carbons with advanced porosity (narrow micropore: 0.37–0.42 cm3/g), high heteroatom content (N content: 8.54 at% and 8.87 wt% and S content: 0.86 at% and 1.73 wt%) and remarkable yield (57.12–69.13 wt%) was produced using lignin as the raw material via a synergistic strategy involving melamine modification and CuCl2 activation. Notably, melamine modification not only introduced mesopores, but also promoted the effect of CuCl2 activation to generate additional micropores. Importantly, the advanced porosity required a low dosage of CuCl2. The optimized adsorbent (NHPC-850) exhibits outstanding CO2 adsorption capacity (6.87 mmol/g at 273 K and 100 kPa, 3.57 mmol/g at 303 K and 100 kPa), a moderately high heat of adsorption (34.7 kJ/mol), and an extraordinary CO2/N2 selectivity (132 at 273 K/81 at 303 K). These excellent properties are attributed to the well-developed micropores and suitable mesopores of carbon materials, as well as rich nitrogen and sulfur functionality in the carbon structure. Collectively, this work offers new insights into a simple and easy-to-scale strategy for the preparation of biomass-derived N, S co-doped hierarchical porous carbon.

Preparation of novel green adsorbent (Tabernaemontana divaricata leaf powder) and evaluation of its dye (malachite green) removal capacity, mechanism, kinetics, and phytotoxicity

In this study, a novel green adsorbent, Tabernaemontana divaricata leaf powder (TD), was prepared, and its efficacy in removing malachite green (MG) dye from water, along with the associated mechanism and kinetics, was systematically evaluated for the first time. Characterization of TD was carried out using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). Optimization of MG dye removal was conducted by varying parameters such as pH, initial dye concentration, contact time, and TD dosage. Results demonstrated that TD exhibited a high adsorption capacity for MG dye (5.2131 mg.g−1), achieving a maximum removal efficiency of 89.5 % under optimized conditions: pH 7.0, initial dye concentration of 20 ppm, contact time of 120 min, TD dosage of 4 g/L, and temperature of 28.1 °C. Kinetic and isotherm models were applied to analyze the experimental data, revealing that the adsorption process most accurately followed Ho's pseudo-second-order kinetic model (R2 = 0.999). The high heats of adsorption observed in the isotherm study suggest prominent electrostatic interactions between adsorbate molecules and the surface, governing the chemisorption mechanism that dominates at the solid-liquid interface. This study underscores the potential of Tabernaemontana divaricata (jasmine) leaf powder as a cost-effective, environmentally friendly, and efficient adsorbent for the remediation of MG dye-contaminated water.

Cross-Linking CdSO4-Type Nets with Hexafluorosilicate Anions to Form an Ultramicroporous Material for Efficient C2H2/CO2 and C2H2/C2H4 Separation.

A 44.610.8 topology hybrid ultramicroporous material (HUM), {[Cu1.5F(SiF6)(L)2.5]·G}n, (L = 4,4'-bisimidazolylbiphenyl, G = guest molecules), 1, formed by cross-linking interpenetrated 3D four-connected CdSO4-type nets with hexafluorosilicate anions is synthesized and evaluated in the context of gas sorption and separation herein. 1 is the first HUM functionalized with two different types of fluorinated sites (SiF6 2- and F- anions) lining along the pore surface. The optimal pore size (≈5Å) combining mixed and high-density electronegative fluorinated sites enable 1 to preferentially adsorb C2H2 over CO2 and C2H4 by hydrogen bonding interactions with a high C2H2 isosteric heat of adsorption (Qst) of ≈42.3kJmol-1 at zero loading. The pronounced discriminatory sorption behaviors lead to excellent separation performance for C2H2/CO2 and C2H2/C2H4 that surpasses many well-known sorbents. Dynamic breakthrough experiments are conducted to confirm the practical separation capability of 1, which reveal an impressive separation factor of 6.1 for equimolar C2H2/CO2 mixture. Furthermore, molecular simulation and density functional theory (DFT) calculations validate the strong binding of C2H2 stems from the chelating fix of C2H2 between SiF6 2- anion and coordinated F- anion.

Improving the Separation of CO2/N2 Using Impregnation of a Deep Eutectic Solvent on a Porous MOF.

As the partial pressure of CO2 in flue gas is 0.1-0.2 bar, CO2 capture at a low pressure needs more attention. Under low pressure conditions, the functional metal-organic framework (MOF) is powerful for CO2 capture. One of the effective methods to increase the absorption capacity of the MOF is impregnation with deep eutectic solvents. In this research, NH2-MIL101(Cr) is impregnated with a deep eutectic solvent of choline chloride:urea (DES ChCl:urea) to enhance the adsorption capacity. The CO2 and N2 adsorption capacity of NH2-MIL101(Cr) and DES/NH2-MIL101(Cr) was investigated at temperatures of 288.15-303.15 K and pressures up to 1 bar. The obtained results indicate that the adsorption capacity of the MOF increases by 1.7 and 3 times with the impregnated DES for CO2 and N2, respectively. Nevertheless, the pore volume of the MOF decreased after impregnation, but the adsorption capacity of the MOF increased due to the interaction of the adsorbate with the confined DES in pores. The contribution of the impregnated DES to adsorption capacity is explained according to Henry's law. Also, high heats of adsorption are attributed to the strong interaction between modified NH2-MIL101(Cr) and CO2. Also, the sample was refined at 298 K and vacuum and was reused without considerable reduction of the CO2 capture capacity after 6 times. Moreover, the impregnation of ChCl:urea into NH2-MIL101(Cr) nanostructures was studied using density functional theory-based approaches.

Study on Adsorption of Diesel Molecules on MoS<sub>2</sub> and NiMoS Catalysts

For deep insight into complex reaction system of diesel hydrotreating, the monolayer adsorption and competitive adsorption of typical reactant molecules (phenanthrene, naphthalene, acridine, quinoline, dibenzothiophene, 4,6-dimethyldibenzothiophene and H2) on MoS2 and NiMoS catalyst models with different structures were investigated. The basal plane is discovered to be the best physical adsorption position for all molecules in MoS2 series catalysts. Following saturation of the basal plane, reactant molecules will be adsorbed at Mo edge first, and Mo edge is more prone to bimolecular or multimolecular adsorption than S-edge, implying that Mo edge active sites play an important role in diesel hydrotreating. Naphthalene has a higher adsorption capacity in the partial pressure system that simulates the actual reaction atmosphere, and it is the most likely reactant molecule to predominately occupy active sites, but 4,6-dimethyl dibenzothiophene still exhibits good competition adsorption performance due to its high adsorption capacity and heat release. Interestingly, after phenanthrene adsorption, the secondary adsorption of hydrogen decreases in all of the catalyst models studied, indicating that phenanthrene is one of the most important molecules influencing hydrogen adsorption. Furthermore, the secondary adsorption of hydrogen after phenanthrene adsorption decreased the most on Tri-S50 catalyst. It shed light on that the activity and stability of Tri-S50 catalyst was most likely to decrease during diesel hydrotreating because of the notable inhibition on adsorption of hydrogen molecules brought by phenanthrene adsorption. It presents a theoretical basis for the design and development of highly efficient diesel hydrotreating catalysts.

Investigating the impact of pore structure and surface chemistry on CO2 adsorption in graphitic slit-pores using GCMC simulation

Carbon capture, storage, and utilization from post-combustion processes using adsorption phenomena has emerged as a promising solution to the greenhouse gas emission crisis. The capacity of solid porous adsorbents dictates the performance of such carbon capture processes. Developments of porous adsorbents with favourable structural and chemical characteristics of the pore have been a major research area. Computational tools, notably the Grand Canonical Monte Carlo (GCMC) simulation, are widely employed to characterize the adsorption process in crystalline adsorbents like metal-organic frameworks and zeolites. Activated carbons are becoming promising alternatives to conventionally-used zeolite adsorbents for CO2 adsorption, because of their abundant microporosity and cost performance. However, the amorphous nature of the activated carbon materials poses a challenge in accurately modelling their pore characteristics and their adsorption process. Therefore, this study systematically explores the effect of pore size distribution and type of functional groups on the adsorption of CO2 on activated carbons using a simplified slit-pore graphite structure representing the activated carbon adsorbent. Four different pore sizes (7 Å, 8.9 Å, 18.5 Å, and 27.9 Å) and three oxygen-containing functional groups (Carbonyl, Hydroxyl, and Carboxyl) were selected to model the graphite structures. Results from the GCMC simulation reveal a significant rise in the CO2 adsorption capacity (from 4 mmol/g to 21 mmol/g) as the pore size was increased from 7 Å to 27.9 Å. Likewise, the functional groups enhance the low-pressure adsorption process by reducing the onset pressure of the pore filling by a factor of 100, especially in ultra-micropores. Likewise, we demonstrate the increase in the isosteric heat of adsorption due to the reduction in the pore size and the presence of functional groups. Additionally, the study illustrates the adsorbed phase behaviour of CO2 concerning the pore characteristics, a facet often overlooked in the existing literature. The adsorbed phase local density and molecular orientation distribution are analysed to understand the variation in the adsorption uptake and isosteric heat of adsorption properties. The study further identifies the adsorbed phase monolayer to multilayer transition and the ‘T′-shaped orientation of the adsorbed CO2 molecules as the key contributors to the high isosteric heat of adsorption in 8.9 Å pore size. It is envisaged that this study will navigate the precision adsorbent development for an efficient carbon capture process.

Air-Stable Cu(I) Metal-Organic Framework for Hydrogen Storage.

Metal-organic frameworks (MOFs) that contain open metal sites have the potential for storing hydrogen (H2) at ambient temperatures. In particular, Cu(I)-based MOFs demonstrate very high isosteric heats of adsorption for hydrogen relative to other reported MOFs with open metal sites. However, most of these Cu(I)-based MOFs are not stable in ambient conditions since the Cu(I) species display sensitivity toward moisture and can rapidly oxidize in air. As a result, researchers have focused on the synthesis of new air-stable Cu(I)-based materials for H2 storage. Here, we have developed a de novo synthetic strategy to generate a robust Cu(I)-based MOF, denoted as NU-2100, using a mixture of Cu/Zn precursors in which zinc acts as a catalyst to transform an intermediate MOF into NU-2100 without getting incorporated into the final MOF structure. NU-2100 is air-stable and displays one of the initial highest isosteric heats of adsorption (32 kJ/mol) with good hydrogen storage capability under ambient conditions (10.4 g/L, 233 K/100 bar to 296 K/5 bar). We further elucidated the H2 storage performance of NU-2100 using a combination of spectroscopic analysis and computational modeling studies. Overall, this new synthetic route may enable the design of additional stable Cu(I)-MOFs for next-generation hydrogen storage adsorbents at ambient temperatures.

Experimental Study and Thermodynamic Analysis of Carbon Dioxide Adsorption onto Activated Carbons Prepared from Biowaste Raw Materials

Nutshells are regarded as cost-effective and abundant raw materials for producing activated carbons (ACs) for CO2 capture, storage, and utilization. The effects of carbonization temperature and thermochemical KOH activation conditions on the porous structure as a BET surface, micropore volume, micropore width, and pore size distribution of ACs prepared from walnut (WNS) and hazelnut (HNS) shells were investigated. As a result, one-step carbonization at 900/800 °C and thermochemical KOH activation with a char/KOH mass ratio of 1:2/1:3 were found to be optimal for preparing ACs from WNS/HNS: WNS-AC-3 and HNS-AC-2, respectively. The textural properties of the WNS/HNS chars and ACs were characterized by low-temperature nitrogen vapor adsorption, XRD, and SEM methods. Dubinin’s theory of volume filling of micropores was used to evaluate the microporosity parameters and to calculate the CO2 adsorption equilibrium over the sub- and supercritical temperatures from 216.4 to 393 K at a pressure up to 10 MPa. The CO2 capture capacities of WNS- and HNS-derived adsorbents reached 5.9/4.1 and 5.4/3.9 mmol/g at 273/293 K under 0.1 MPa pressure, respectively. A discrepancy between the total and delivery volumetric adsorption capacities of the adsorbents was attributed to the strong binding of CO2 molecules with the adsorption sites, which were mainly narrow micropores with a high adsorption potential. The high initial differential heats of CO2 adsorption onto ACs of ~32 kJ/mol confirmed this proposal. The behaviors of thermodynamic functions (enthalpy and entropy) of the adsorption systems were attributed to changes in the state of adsorbed CO2 molecules determined by a balance between attractive and repulsive CO2–CO2 and CO2–AC interactions during the adsorption process. Thus, the chosen route for preparing ACs from the nutshells made it possible to prepare efficient carbon adsorbents with a relatively high CO2 adsorption performance due to a substantial volume of micropores with a size in the range of 0.6–0.7 nm.

The influence of zeolite pore topology on the separation of carbon dioxide from methane

The influence of framework topology on the separation of carbon dioxide from methane has been studied in a set of small pore pure silica zeolites with CHA, IHW, ITW, LTA, MTF and RWR structures. To isolate this effect, the composition of the materials has been kept constant by using pure silica materials, which have neither aluminium in their framework nor extraframework cations that can alter the adsorption behaviour. Pure component adsorption isotherms and breakthrough experiments with synthetic mixtures resembling biogas and natural gas have been conducted. Materials Si-RWR and Si-ITW, which present channel-like topology, show higher IAST selectivities towards CO2 due to a kinetic exclusion of methane, which in the case of Si-RWR is pore-size based and in the case of Si-ITW, topology based. High heat of adsorption of CO2 on Si-ITW is explained through a maximisation of the dispersive interactions between the tight channels and the adsorbate. The extremely small pores of Si-RWR lead to a reduced diffusivity not only of CH4 but also of CO2 precluding its use as adsorbent for this separation. Si-ITW arises as a promising material in the separation of CO2 from CH4, having high selectivity towards CO2 while keeping high diffusion rates and a moderate maximum capacity. A comparison of the performance of these materials with that of aluminosilicate zeolites LTA with Si/Al ratio of 5 and 13X shows that Si-ITW can be more convenient by lowering the energetic requirements of the regeneration step. Moreover, the hydrophobicity of this material can be a further advantage over traditional zeolites.

Structural engineering of NiFe-Layered double hydroxides and halloysite composites for efficient CO2 capture

The cost- and use-effects for solid CO2 adsorbents have accelerated development of the clay-based adsorbents. Herein, a series of NiFe-layered double hydroxides/halloysite (NiFe-LDH/Hal) composites were fabricated via facile hydrothermal strategy using calcined halloysites (Hal) as supports. Depending on treatment temperatures of halloysite, the supported NiFe-LDH exhibited different morphologies in form of nanoparticle or intertwined nanosheets. Based on the distinct morphology, these NiFe-LDH/halloysite composites displayed different textural properties and CO2 adsorption performance. Particularly, the sample NiFe-LDH/Hal600 using halloysite calcined at 600 °C as support possessed 3D hierarchical structure, and displayed superior CO2 adsorption capacity of 60.7 mg g−1 and 40.3 mg g−1 at 273 K and 298 K, respectively, much higher than those of NiFe-LDH/Hal composites supporting LDH nanoparticles. The high isosteric heat of adsorption calculated from Clausius-Clapeyron equation (21.7 kJ mol−1) indicated the strong interaction between basic NiFe-LDH surface and CO2 molecules. It was validated that the dehydroxylation and forming of silanols groups during calcination process changed the activity of internal and external surface, resulting in distinct morphology and distribution difference of the supported NiFe-LDH. The prepared clay-based composites displayed satisfying recyclability of CO2 adsorption at a high retention level after 25 cycles of adsorption–desorption.

Influence of chain length on structural properties of carbon molecular sieving membranes and their effects on CO[formula omitted], CH[formula omitted] and N[formula omitted] adsorption: A molecular simulation study

Carbon molecular sieving membranes (CMSM) derived from 6FDA/BPDA-DAM polymer precursors (6F-CMSM) show excellent adsorption and selectivity towards CO2. Using molecular dynamics (MD) simulations, we investigate how the length of individual carbon chains determines the morphologies emerging from the same monomers. Smaller chains produce densely packed structures, whereas longer chains arrange in layers, creating larger voids comprising both micropores and ultra-micropores. The pure gas adsorption isotherms of CO2, CH4, and N2 inside various 6F-CMSM morphologies, obtained from MD, provide theoretical insights into most feasible structures formed in experiments, thereby providing an estimate of the corresponding 6F-CMSM density. Using grand canonical Monte Carlo simulations, we observe that high isosteric heats of adsorption for CO2 leads to enhanced adsorption capacity and high sorption selectivity from binary mixtures of these gases. Studying the asphericity of carbon chains, we report the existence of an optimum chain length of highest curvature, leading to low density, high porosity, and high CO2 adsorption capacities that compare well with available experimental data, without compromising sorption selectivity of 6F-CMSM. This work provides a theoretical basis of how slight modifications of the physical arrangements of chemical components lead to significant changes in porosity and gas adsorption capacities of molecular sieving membranes.

Valorization of orange peel waste to tunable heteroatom-doped hydrochar-derived microporous carbons for selective CO2 adsorption and separation

Constrained by the extortionately expensive carbon sources, low carbon yields, inadequate adsorption capacities, and corrosive chemical activating agents, the commercialization of carbonaceous CO2 adsorbents remains a challenging task. Herein, potassium oxalate (K2C2O4), an activating agent with less corrosive properties, was used for the synthesis of activated carbons from inexhaustibly available “orange peel biowaste.” For the first time, a comprehensive report is presented on the effect of hydrothermal treatment, hydrochar/K2C2O4 ratio, activation temperature, and melamine modification in tailoring the porosity and surface functionalization of activated carbons. The optimized sample, OPMK-900, exhibited large specific surface area ~2130 m2/g; micropore volume ~1.1166 cm3/g, and a high pyrrolic nitrogen content (~ 46.1 %). Notably, melamine played the dual role as a promoter to K2C2O4 porosity generation and a nitrogen dopant, which synergistically led to an efficient CO2 uptake of ~6.67 mmol/g at 273 K/ 1 bar via micropore-filling mechanism and Lewis acid–base interactions. Moreover, remarkably high IAST CO2/N2 selectivity (105 at 273 K and 96 at 298 K) surpasses most of the biomass-derived carbons. Furthermore, the moderately high isosteric heat of adsorption (∆Hads ~ 38.9 kJ/mol) revealed the physisorption mechanism of adsorption with a limited energy requirement for the regeneration of the spent adsorbents.

Strategic Design of Mg-Centered Porphyrin Metal-Organic Framework for Efficient Visible Light-Promoted Fixation of CO2 under Ambient Conditions: Combined Experimental and Theoretical Investigation.

The sunlight-driven fixation of CO2 into valuable chemicals constitutes a promising approach toward environmental remediation and energy sustainability over traditional thermal-driven fixation. Consequently, in this article, we report a strategic design and utilization of Mg-centered porphyrin-based metal-organic framework (MOFs) having relevance to chlorophyll in green plants as a visible light-promoted highly recyclable catalyst for the effective fixation of CO2 into value-added cyclic carbonates under ambient conditions. Indeed, the Mg-centered porphyrin MOF showed good CO2 capture ability with a high heat of adsorption (44.5 kJ/mol) and superior catalytic activity under visible light irradiation in comparison to thermal-driven conditions. The excellent light-promoted catalytic activity of Mg-porphyrin MOF has been attributed to facile ligand-to-metal charge transfer transition from the photoexcited Mg-porphyrin unit (SBU) to the Zr6 cluster which in turn activates CO2, thereby lowering the activation barrier for its cycloaddition with epoxides. The in-depth theoretical studies further unveiled the detailed mechanistic path of the light-promoted conversion of CO2 into high-value cyclic carbonates. This study represents a rare demonstration of sunlight-promoted sustainable fixation of CO2, a greenhouse gas into value-added chemicals.

An overview of the role of supramolecular interactions in gas storage using MOFs

This work aims to provide a complete understanding of how different supramolecular interactions in metal–organic frameworks (MOFs): Hydrogen bonds (HBs), dipole–dipole (D-D) interactions, van der Waals forces (VWFs), π stacking, π*–n interactions, as well as coordination bonds (CBs) have repercussion on the adsorption of different gases (H2, CO2, CH4, hydrocarbons, SO2 and SH2). We conclude that a small pore size increases the binding energy with guest molecules due to an increase in van der Waals interaction (VWIs). A large aromatic system produces strong interactions with guest molecules but increases pore size. The functional groups on the linkers can promote the guest molecules' adsorption by changing the linkers' electronic density, which increases the polarization of the guest molecules, creating a specific interaction such as HBs with the guest molecules. Regarding CBs, it depends on the metal's electronic configuration. A high isosteric adsorption heat (indicative of a stronger interaction) does not always explain a high gas uptake; a high isosteric adsorption heat is more likely to be the main factor explaining the material selectivity towards a given gas.

WATERMELON PEEL EXTRACT AS GREEN CORROSION INHIBITOR FOR ST-37 CARBON STEEL IN SEAWATER

Corrosion engineering has taken great interest in many industries that required high cost management to overcome the serious problems. This work has investigated the role of watermelon peel extract as green inhibitor to protect carbon steel in seawater. This investigation has studied the corrosion rate and inhibition efficiency applying weight loss method. The laboratory result shows the optimum inhibition efficiency found to be 71.64% at 5% inhibitor concentration in 100 ml seawater at room temperature. The effects of temperature and immersion time on inhibition efficiency have also been examined. This study has used Arrhenius equation based on activation energy to determine type of adsorption encountered with corrosion process. The result shows a chemical adsorption justified by its high adsorption heat and strengthened by FTIR and UV-Vis examinations. The phytochemical examination of watermelon peel extract gives positive response to flavonoid, alkaloid, and saponin. The finding is useful for many industries encountered with carbon steel corrosion in corrosive medium using green inhibitor.

Interpenetration Symmetry Control Within Ultramicroporous Robust Boron Cluster Hybrid MOFs for Benchmark Purification of Acetylene from Carbon Dioxide.

The separation of C2 H2 /CO2 is an important process in industry but challenged by the trade-off of capacity and selectivity owning to their similar physical properties and identical kinetic molecular size. We report the first example of symmetrically interpenetrated dodecaborate pillared MOF, ZNU-1, for benchmark selective separation of C2 H2 from CO2 with a high C2 H2 capacity of 76.3 cm3 g-1 and record C2 H2 /CO2 selectivity of 56.6 (298 K, 1 bar) among all the robust porous materials without open metal sites. Single crystal structure analysis and modeling indicated that the interpenetration shifting from asymmetric to symmetric mode provided optimal pore chemistry with ideal synergistic "2+2" dihydrogen bonding sites for tight C2 H2 trapping. The exceptional separation performance was further evidenced by simulated and experimental breakthroughs with excellent recyclability and high productivity (2.4 mol kg-1 ) of 99.5 % purity C2 H2 during stepped desorption process.

Fingerprinting diverse nanoporous materials for optimal hydrogen storage conditions using meta-learning.

Adsorptive hydrogen storage is a desirable technology for fuel cell vehicles, and efficiently identifying the optimal storage temperature requires modeling hydrogen loading as a continuous function of pressure and temperature. Using data obtained from high-throughput Monte Carlo simulations for zeolites, metal-organic frameworks, and hyper-cross-linked polymers, we develop a meta-learning model that jointly predicts the adsorption loading for multiple materials over wide ranges of pressure and temperature. Meta-learning gives higher accuracy and improved generalization compared to fitting a model separately to each material and allows us to identify the optimal hydrogen storage temperature with the highest working capacity for a given pressure difference. Materials with high optimal temperatures are found in close proximity in the fingerprint space and exhibit high isosteric heats of adsorption. Our method and results provide new guidelines toward the design of hydrogen storage materials and a new route to incorporate machine learning into high-throughput materials discovery.

Role of heteroatoms (nitrogen and sulfur)-dual doped corn-starch based porous carbons for selective CO2 adsorption and separation

Herein, we have produced two series of novel materials including heteroatoms-doped (thiourea-modified) and heteroatoms-deprived microporous carbons using three different potassium salts activators (KOH, K2CO3, K2C2O4). The experimental results reveal that thiourea-modified KOH activated sample exhibit excellent textural features (specific surface area∼1795 m2/g, micropore volume∼0.82 cm3/g) but at the expense of a reduced heteroatom content. However, sample prepared with K2C2O4 exhibited a comparable specific surface area (∼1747 m2/g), enough population of narrow micropores (<1.0 nm), the highest micropore volume (0.93 cm3/g) and a high nitrogen (4.6 at. %) and sulfur content (2.3 at. %). Therefore, the optimized sample, STO, exhibits remarkable CO2 adsorption (269.61 mg/g at 0 °C and 1 bar), excellent IAST CO2/N2 selectivity (73), high isosteric heat of adsorption (39.3 kJ/mol) and high cyclic stability, surpassing the CO2 adsorption/separation performance of most of the biomass-derived carbons. Herein, for the first time, a comprehensive study on potassium salts activation, in comparison with the conventionally practiced KOH activation, is presented. Concluding, the experimental results unveiled K2C2O4 as a more competitive and less corrosive potassium salt activating agent by virtue of its ability to fabricate N, S dual-doped highly porous carbons for efficient CO2 adsorption and separation.

A rational design of cellulose-based heteroatom-doped porous carbons: Promising contenders for CO2 adsorption and separation

The present work demonstrates a facile synthesis of cellulose-based novel microporous carbons (Cell-X) for environmental remediation by virtue of their application as CO2 adsorbents. The presence of heteroatoms (N, S) in highly porous carbon frameworks (1032 m2/g) endowed Cell-X with efficient CO2 adsorption and separation characteristics. The optimized sample, Cell-UK, exhibit significantly large micropore volume (0.7135 cm3/g), abundance of narrow micropores (<0.94 nm) and optimum pyrrolic nitrogen content (58%) which leads to efficient CO2 adsorption (297.1 mg/g at 273 K and 193.7 mg/g at 298 K/1 bar) and moderately high heat of adsorption (36.70 kJ/mol). Additionally, ideal adsorbed solution theory (IAST) determines a CO2/N2 selectivity ~ 110 at 298 K, surpassing the gas separation performance of most reported microporous carbons. Herein, the remarkable CO2 adsorption and separation performance of prepared materials is attributed to the synergistic role of narrow micropores (<0.94 nm) and surface heterogeneity (N/N, S-doped surfaces). These heteroatoms enriched basic sites induced stronger affinity for acidic CO2 molecules by generating Lewis acid-base interactions between gas molecules and adsorbent surfaces. Conclusively, present work demonstrates an effort devoted to the rational designing of tunable porous cellulose-based CO2 adsorbents as promising contenders to mitigate global warming.