Motivated by the recent successful synthesis of biphenylene structure [Science 372, (2021), 852], we have explored the sensing properties of this material towards the catechol biomolecule by performing the first-principles density functional theory and molecular dynamics simulations. Pristine biphenylene sheet adsorbs catechol molecule with a binding energy of -0.35 eV, which can be systematically improved by decorating the transition metals (Ag, Au, Pd, and Ti) at various possible sites of biphenylene. It is observed that the catechol molecule is adsorbed on Pd and Ti-decorated biphenylene sheets with a strong adsorption energy of -1.00 eV and -2.54 eV, respectively. The interaction of the catechol molecule with biphenylene and metal-decorated biphenylene is due to the charge transfer from the O-2p orbitals of the catechol molecule, to the C-2p orbitals of biphenylene and d-orbitals of metals in metal-decorated biphenylene, respectively. From the Bader charge calculation, we found that 0.05e amount of charge is transferred from the catechol molecule to pristine biphenylene, which gets almost double (~0.1e) for the Ti-decorated biphenylene sheet. The diffusion energy barrier for the clustering of the Pd and Ti atoms comes out to be 2.39 eV and 4.29 eV, computed by performing the climbing-image nudged elastic band calculations. We found that the catechol molecule gets desorbed from the pristine biphenylene sheet even at 100 K but remains attached to metal (Pd, Ti) decorated biphenylene sheets at room temperature by performing the ab-initio molecular dynamics simulations. The Ti-decorated biphenylene sheet has more sensitivity toward catechol adsorption while the Pd-decorated biphenylene sheet has a suitable recovery time at 500 K. The results suggest that the Pd and Ti-decorated biphenylene sheets are promising materials for catechol detection.

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By performing the density functional theory simulations, we have studied the H2 adsorption and desorption properties of the Ti‐functionalized holey graphyne system. The simulation results revealed that the Ti atom is bonded strongly to the holey graphyne sheet with a binding energy of −4.16 eV through the Dewar interaction. The Ti‐functionalized holey graphyne can capture 7H2 molecules with an average H2 adsorption energy of −0.38 eV/H2, leading to a hydrogen gravimetric density of 10.52 wt%. The average desorption temperature is computed by the Van't Hoff relation and obtained to be 486 K, optimum for practical applications. The adsorbed H2 molecules are attached with the Ti‐functionalized holey graphyne via the Kubas interactions involving charge donation and back donation between Ti‐3d orbitals and H‐1 s orbital. Subsequently, the ab initio molecular dynamics simulations have been conducted to verify the structural constancy of the storage media. We have found a sufficiently high energy barrier of 2.3 eV that prevents the system from metal‐metal clustering. Therefore, the Ti‐functionalized holey graphyne can be utilized as a promising high‐capacity reversible hydrogen storage medium.

Catechol is a toxic biomolecule due to its low degradability to the ecosystem and unpredictable impact on human health. In this work, we have investigated the catechol sensing properties of pristine and transition metal (Ag, Au, Pd, and Ti) decorated γ-graphyne (GY) systems by employing the density functional theory and first-principles molecular dynamics approach. Simulation results revealed that Pd and Ti atom is more suitable than Ag and Au atom for the decoration of the GY structure with a large charge transfer of 0.29e and 1.54e from valence d-orbitals of the Pd/Ti atom to the carbon-2p orbitals of GY. The GY + Ti system offers excellent electrochemical sensing towards catechol with charge donation of 0.14e from catechol O-p orbitals to Ti-d orbitals, while the catechol molecule is physisorbed to pristine GY with only 0.04e of charge transfer. There exists an energy barrier of 5.19 eV for the diffusion of the Ti atom, which prevents the system from metal–metal clustering. To verify the thermal stability of the sensing material, we have conducted the molecular dynamics simulations at 300 K. We have reported feasible recovery times of 2.05 × 10−5 s and 4.7 × 102 s for sensing substrate GY + Pd and GY + Ti, respectively, at 500 K of UV light.