Computational Screening Points to Tungsten-Modified Carbon Nitride for HCN Capture

Hydrogen cyanide is one of the most dangerous gases that industry releases into the atmosphere, and a new computational mini-review argues that a familiar carbon-based material, carefully decorated with transition metal atoms, may be the key to detecting and capturing it. The review, published in the journal Carbon Neutral Systems, uses density functional theory (DFT) to systematically compare how hydrogen cyanide (HCN) interacts with a wide range of adsorbent platforms, from pristine graphene to doped nanotubes and metal-modified graphitic carbon nitride. Its headline conclusion is striking: among all the modified systems surveyed, tungsten-modified graphitic carbon nitride (g-C3N4) shows the strongest interaction with HCN, achieving an adsorption energy of −3.104 eV, the most negative value reported among the doped versions examined.

The stakes are high. According to the review, HCN can be lethal at concentrations as low as 300 ppm within minutes of exposure, and it is particularly insidious because it is colorless, odorless, and tasteless, making it nearly impossible for most people to detect without instrumentation. The authors note that most individuals lack the genetic ability to smell the compound, which raises the risk of accidental poisoning. Once inhaled or absorbed through the skin, HCN disrupts cellular respiration by binding to cytochrome oxidase, depriving cells of oxygen rapidly. These properties make reliable sensor technologies and effective removal methods essential for both occupational safety and environmental protection.

HCN occupies a dual role in modern industry. It is a widely used chemical in synthesis, metallurgy, and pharmaceutical production, yet it is also a byproduct of fossil fuel combustion and various industrial processes. Its linear molecular structure, H–C≡N, and high reactivity demand advanced monitoring and removal technologies. The review surveys the existing toolbox: combustion can handle high-concentration streams but requires temperatures above 500 °C and risks generating nitrogen oxide byproducts; catalytic hydrolysis and oxidation convert HCN into less harmful compounds such as N2, H2O, and NH3 at lower temperatures, but suffer from catalyst poisoning by ammonia and sulfur compounds; and biological treatment through biofiltration offers a sustainable alternative, though microbial systems require careful maintenance to prevent clogging or drying of the filter bed.

Against this backdrop, adsorption stands out as the preferred strategy in the authors’ assessment, thanks to its operational simplicity, cost-effectiveness, and high efficiency, particularly when advanced nanomaterials are used. The review catalogs a decade of DFT findings on candidate materials. Silicon carbide nanotubes bind HCN with a binding energy of about 0.7 eV, inducing charge transfer that significantly alters their conductivity. Aluminum-doped graphene shows strong HCN sensitivity, and boron nitride nanotubes, in their pure form, adsorb HCN only weakly at −0.2474 eV, but transition-metal doping with nickel, palladium, or platinum strengthens the interaction considerably, with platinum-doped nanotubes showing the most negative interaction energy among those doped systems.

Phosphorene provides another instructive comparison. Pure phosphorene adsorbs HCN with an energy of −0.249 eV, but doping with aluminum or silicon dramatically enhances the interaction, yielding adsorption energies of −0.879 eV and −0.924 eV respectively. Sulfur doping, by contrast, degrades performance to just −0.169 eV with a larger atomic separation of 3.452 Å. Similar patterns emerge across the periodic table of dopants: aluminum-rich aluminum nitride nanotubes interact with HCN where pure ones barely do; silicon-doped graphene reaches an optimal adsorption energy of roughly −10.1 kcal/mol; and magnesium- and calcium-doped beryllium oxide nanotubes show enhanced sensitivity relative to undoped tubes through significant net charge transfer.

The central material of the review, graphitic carbon nitride, is a semiconductor with a heptazine-based structure that the authors describe as more stable than other C3N4 allotropes. Its unit cell contains six carbon and eight nitrogen atoms with three distinct nitrogen types—edge, bridge, and inner—arranged around a relaxed lattice parameter of 7.40 Å, consistent with both theoretical predictions and experimental data. The material’s advantages include tunable band-gap energy, enhanced gas absorption capacity, favorable pore size distribution, and cost-effectiveness. Earlier DFT work cited in the review showed that nickel, palladium, and platinum doping transforms HCN adsorption on g-C3N4, with platinum-doped systems demonstrating particularly high adsorption energy and stronger electronic signatures near the Fermi level than their nickel-doped counterparts.

A fascinating structural detail unifies much of this work: when HCN adsorbs onto pure or transition-metal-doped g-C3N4, the planar sheet bends. The review emphasizes that this planar-to-curved transformation produces configurations with greater thermodynamic stability than the original flat structures. Palladium and platinum atoms maintain nearly symmetric positions within the g-C3N4 cavities, while nickel atoms adopt asymmetric coordination geometries and show reduced stability due to strong covalent nitrogen bonding. Partial density of states analysis reveals that in pure g-C3N4, the 2p and 2s orbitals of edge nitrogen atoms change minimally near the Fermi energy after HCN adsorption, indicating only weak interaction, whereas metal-doped systems develop sharp peaks near the Fermi level that correlate with stronger binding.

The newest computational results in the review extend this strategy to chromium, molybdenum, and tungsten modification of heptazine-based g-C3N4. Relaxed-geometry analysis showed that molybdenum and tungsten atoms sit nearly symmetrically within the g-C3N4 cavities, while chromium induces an asymmetric coordination environment. Doping and HCN adsorption together generate new electronic states near the Fermi level, and because the conduction and valence bands cross that level, the modified systems exhibit metallic conductivity—a property highly desirable for resistive gas sensing. Among the three metals, tungsten produced the strongest HCN interaction, with the adsorption energy of −3.104 eV surpassing both chromium- and molybdenum-doped counterparts. The authors attribute this to orbital overlap between tungsten and the adsorbing molecule, consistent with earlier findings that tungsten’s 5d orbitals form strong chemical bonds with nitrogen 2p orbitals in related doped graphene systems.

The review is careful to frame these results as computational predictions rather than demonstrated devices. DFT provides a one-particle description of multi-particle systems that simplifies calculations of electronic behavior and geometric structure, offering cost advantages over experimental approaches, but the authors explicitly state that future research must focus on the large-scale synthesis of these frameworks and their long-term stability under varying environmental conditions before the computational insights can translate into practical industrial applications. The goal, they argue, is a class of ‘smart’ adsorbents capable of both high-capacity capture and real-time sensing, bridging the gap between laboratory discovery and industrial-scale detoxification systems.

Even within its computational scope, the review’s comparative tables carry weight for researchers designing the next generation of gas sensors and remediation materials. The survey spans activated carbon modified with copper, cobalt phthalocyanine, and cerium for combined hydrolysis and oxidation; manganese-titanium oxide catalysts achieving complete HCN conversion at 200 °C; copper-manganese oxide catalysts decomposing HCN at temperatures as low as 80 °C; and boron- and phosphorus-doped graphene nanoribbons showing 15- and 12-fold increases in adsorption energy over pure ribbons. By placing tungsten-modified g-C3N4 at the top of this energetic hierarchy, the mini-review offers the sensor and remediation communities a clear, quantitatively grounded starting point: a structurally simple, chemically stable semiconductor whose adsorption profile can be tuned from passive to highly active through deliberate transition metal engineering.

Subject of Research: Density functional theory screening of adsorbent materials for hydrogen cyanide removal

Article Title: A DFT-based mini-review on adsorbent materials for hydrogen cyanide removal

Article References: Madadi-Atmiansofla, F., Babapoor, A., Basharnavaz, H., & Hashemi, S. H. (2026). A DFT-based mini-review on adsorbent materials for hydrogen cyanide removal. Carbon Neutral Systems, 2(1), Article 13. https://doi.org/10.1007/s44438-026-00034-2

Image Credits: AI Generated

DOI: 10.1007/s44438-026-00034-2

Keywords: hydrogen cyanide, DFT, graphitic carbon nitride, adsorption, gas sensors, transition metal doping, tungsten, environmental remediation, toxic gas detection, computational chemistry, nanomaterials, DFT-based