Charged-Controlled Separation of Nitrogen from Natural Gas Using Boron Nitride Fullerene

Natural gas (the main component is methane) has been widely used as a fuel and raw material in industry. Removal of nitrogen (N₂) from methane (CH₄) can reduce the cost of natural gas transport and improve its efficiency. However, their extremely similar size increases the difficulty of separating N₂ from CH_4. In this study, we have performed a comprehensive investigation of N₂ and CH₄ adsorption on different charge states of boron nitride (BN) nanocage fullerene, B₃₆N₃₆, by using a density functional theory approach. The calculational results indicate that B₃₆N₃₆ in the negatively charged state has high selectivity in separating N₂ from CH₄. Moreover, once the extra electron is removed from the BN nanocage, the N₂ will be released from the material. This study demonstrates that the B₃₆N₃₆ fullerene can be used as a highly selective and reusable material for the separation of N₂ from CH₄. The study also provides a clue to experimental design and application of BN nanomaterials for natural gas purification

Porous Polyethersulfone-Supported Zeolitic Imidazolate Framework Membranes for Hydrogen Separation

ZIF-8 thin layer has been synthesized on the asymmetric porous polyethersulfone (PES) substrate via secondary seeded growth. Continuous and dense ZIF-8 layer, containing microcavities, has good affinity with the PES support. Single gas permeance was measured for H₂, N₂, CH₄, O₂, and Ar at different pressure gradients and temperatures. Molecular sieving separation has been achieved for selectively separating hydrogen from larger gases. At 333 K, the H₂ permeance can reach ∼4 × 10^–7 mol m^–2 s^–1 Pa^–1, and the ideal separation factors of H₂ from Ar, O₂, N₂, and CH₄ are 9.7, 10.8, 9.9, and 10.7, respectively. Long-term hydrogen permeance and H₂/N₂ separation performance show the stable permeability of the derived membranes

Graphyne and Graphdiyne: Versatile Catalysts for Dehydrogenation of Light Metal Complex Hydrides

The interaction between new two-dimensional carbon allotropes, i.e., graphyne (GP) and graphdiyne (GD), and light metal complex hydrides LiAlH₄, LiBH₄, and NaAlH₄ was studied using density functional theory (DFT) incorporating long-range van der Waals dispersion correction. The interaction of light metal complex hydrides with GP and GD is much stronger than that with fullerene because of the well-defined pore structure of GP and GD. Such strong interactions greatly affect the degree of charge donation from the alkali metal atom to AlH₄ or BH₄, consequently destabilizing the Al–H or B–H bonds. Compared to the isolated light metal complex hydride, the presence of GP or GD can lead to a significant reduction of the hydrogen removal energy. Most interestingly, the hydrogen removal energies for LiBH_<i>x</i> on GP and with GD are found to be lowered at all the stages (<i>x</i> from 4 to 1), whereas the H-removal energy in the third stage is increased for LiBH₄ on fullerene. In addition, the presence of uniformly distributed pores on GP and GD is expected to facilitate the dehydrogenation of light metal complex hydrides. The present results highlight new interesting materials to catalyze light metal complex hydrides for potential application as media for hydrogen storage. Because GD has been successfully synthesized in a recent experiment, we hope the present work will stimulate further experimental investigations in this direction

Simplest MOF Units for Effective Photodriven Hydrogen Evolution Reaction

Metal–organic frameworks (MOFs) combining the merits of both organic and inorganic functional building structures are fundamentally important and can meet the requirement of vast scientific and technological applications. Intrigued from the fact that transition metals (TMs) are widely embedded in the carbon sp² network or strongly interact with a bare graphene edge, the single transition metal atom may work as a linker to connect carbon chains to build nanoarchitectures. A new MOF building structure, [Metal–Carbon–(Benzene)_<i>i</i>–Chain]_<i>n</i> ring abbreviated as [M-CB_<i>i</i>C]_<i>n</i> (M = Ti, V, and Cr), with increasing carbon chain length <i>i</i> (= 0, 1, 2, ···), was proposed as carbon chains CB<i>_i</i>C connected by a single transition metal atom M to form a ring structure with multiedges <i>n</i> (= 2–6), based on advanced computational methods. They are thermodynamically stable and chemically and physically versatile with ring shape, electronic structures, optical response, as well as hydrogen adsorption energy that vary by changing the length of the carbon chain, the edge number of rings, or the type of connecting metal atoms. The optical response to incoming light of [M-CB_<i>i</i>C]_<i>n</i> rings can be adjustable to cover the entire visible solar spectrum range and exhibit a red shift by either increasing the edge number <i>n</i> or filling the <i>d</i> bands in connecting transition metals. In combination with their ideal adsorption energy of hydrogen atoms, |Δ<i>G</i>_H*|, the proposed [M-CB_<i>i</i>C]_<i>n</i> building structure is attractive for photocatalytic or photoelectrochemical hydrogen evolution applications when they are extended in space to build up 1D, 2D, and 3D MOF frameworks

Dirac State in the FeB₂ Monolayer with Graphene-Like Boron Sheet

By introducing the commonly utilized Fe atoms into a two-dimensional (2D) honeycomb boron network, we theoretically designed a new Dirac material of FeB₂ monolayer with a Fermi velocity in the same order of graphene. The electron transfer from Fe atoms to B networks not only effectively stabilizes the FeB₂ networks but also leads to the strong interaction between the Fe and B atoms. The Dirac state in FeB₂ system primarily arises from the Fe d orbitals and hybridized orbital from Fe-d and B-p states. The newly predicted FeB₂ monolayer has excellent dynamic and thermal stabilities and is also the global minimum of 2D FeB₂ system, implying its experimental feasibility. Our results are beneficial to further uncovering the mechanism of the Dirac cones and providing a feasible strategy for Dirac materials design

Single Molybdenum Atom Anchored on N‑Doped Carbon as a Promising Electrocatalyst for Nitrogen Reduction into Ammonia at Ambient Conditions

Ammonia (NH₃) is one of the most important industrial chemicals owing to its wide applications in various fields. However, the synthesis of NH₃ at ambient conditions remains a coveted goal for chemists. In this work, we study the potential of the newly synthesized single-atom catalysts, i.e., single metal atoms (Cu, Pd, Pt, and Mo) supported on N-doped carbon for N₂ reduction reaction (NRR) by employing first-principles calculations. It is found that Mo₁-N₁C₂ can catalyze NRR through the enzymatic mechanism with an ultralow overpotential of 0.24 V. Most importantly, the removal of the produced NH₃ is rapid with a free-energy uphill of only 0.47 eV for the Mo₁-N₁C₂ catalyst, which is much lower than that for ever-reported catalysts with low overpotentials and endows Mo₁-N₁C₂ with excellent durability. The coordination effect on activity is further evaluated, showing that the experimentally realized active site, single Mo atom coordinated by one N atom and two C atoms (Mo-N₁C₂), possesses the highest catalytic performance. Our study offers new opportunities for advancing electrochemical conversion of N₂ into NH₃ at ambient conditions

Carbon Dioxide Capture and Gas Separation on B₈₀ Fullerene

Exploring advanced materials for efficient capture and separation of CO₂ is important for CO₂ reduction and fuel purification. In this study, we have carried out first-principles density functional theory calculations to investigate CO₂, N₂, CH₄, and H₂ adsorption on the amphoteric regioselective B₈₀ fullerene. Based on our calculations, we find that CO₂ molecules form strong interactions with the basic sites of the B₈₀ by Lewis acid–base interactions, while there are only weak bindings between the other three gases (N₂, CH₄, and H₂) and the B₈₀ adsorbent. The study also provides insight into the reaction mechanism of capture and separation of CO₂ using the electron deficient B₈₀ fullerene

Asymmetrically Decorated, Doped Porous Graphene As an Effective Membrane for Hydrogen Isotope Separation

We propose a new route to hydrogen isotope separation which exploits the quantum sieving effect in the context of transmission through asymmetrically decorated, doped porous graphenes. Selectivities of D₂ over H₂ as well as rate constants are calculated based on ab initio interaction potentials for passage through pure and nitrogen functionalized porous graphene. One-sided dressing of the membrane with metal provides the critical asymmetry needed for an energetically favorable pathway

Auxetic and Ferroelastic Borophane: A Novel 2D Material with Negative Possion’s Ratio and Switchable Dirac Transport Channels

Recently synthesized atomically thin boron sheets (that is, borophene) provide a fascinating template for new material property discovery. Here, we report findings of an extraordinary combination of unusual mechanical and electronic properties in hydrogenated borophene, known as borophane, from first-principles calculations. This novel 2D material has been shown to exhibit robust Dirac transport physics. Our study unveils that borophane is auxetic with a surprising negative Poisson’s ratio stemming from its unique puckered triangle hinge structure and the associated hinge dihedral angle variation under a tensile strain in the armchair direction. Our results also identify borophane to be ferroelastic with a stress-driven 90° lattice rotation in the boron layer, accompanied by a remarkable orientation switch of the anisotropic Dirac transport channels. These outstanding strain-engineered properties make borophane a highly versatile and promising 2D material for innovative applications in microelectromechanical and nanoelectronic devices