First principles study on adsorptive separation and detection of toxic gases by metal-organic framework M-MOF-74 (M=Mg, Zn, Cu)

This study investigates the adsorptive separation and detection of toxic gases (CO, H 2 S, NH 3 , SO 2 , NO, and NO 2 ) on M-MOF-74 (M = Mg, Zn, Cu) using first-principles density functional theory. Periodic PBE-D2 calculations and hybrid-DFT (B3LYP and M06) are employed to evaluate adsorption and detection-related electronic properties. Electronic structure analysis reveals that Mg and Zn-MOF-74 are non-magnetic, whereas Cu-MOF-74 exhibits a 1 μ B magnetic moment, with corresponding band gaps of 1.50, 1.58, and 0.80 eV, confirming their semiconducting nature. Adsorption analysis reveals physisorption for CO, H 2 S, and NH 3 , while SO 2 , NO, and NO 2 undergo chemisorption, except SO 2 on Cu-MOF-74, which also shows physisorption. Detection potential, evaluated through HOMO-LUMO gap variations, density of states, and orbital distributions, indicates promising sensor applications. For Mg and Zn-MOF-74, the HOMO-LUMO gaps decrease substantially by approximately 50-75% upon adsorption of SO 2 , NO, and NO 2 , indicating enhanced electronic interactions and high sensitivity. In contrast, Cu-MOF-74 shows an increase of about 35-55% in the HOMO-LUMO gap for NO and NO 2 adsorption, demonstrating selective detection behavior. Overall, Mg and Zn-MOF-74 exhibit strong potential for detecting SO 2 , NO, and NO 2 , while Cu-MOF-74 shows selective sensitivity toward NO and NO 2 , highlighting their suitability for MOF-based toxic gas sensor applications.