First-principles investigation of ZnCu2Sn(S1-xSex)4 (x = 0.05–0.25) solid solutions for environmental pollutant adsorption: structural optimization and interaction with cement industry pollution (CO2, CO, and SO2)

To solve the increasingly serious issue of global environmental pollution, this study aims to explore the applicability of ZnCu 2 Sn(S 1-x Se x ) 4 (x = 0.05–0.25) solid solutions for industrial waste gas control by adsorption, primarily originating from the cement industry, such as CO 2 , CO, and SO 2 . Using high-level density functional theory (DFT) regarding generalized gradient approximation (GGA), the present work has investigated in detail structural optimization, electronic structure, mechanical stability and adsorption performance against harmful gases such as CO 2 , CO and SO 2 on six different catalyst compositions: ZnCu 2 SnS 4 , ZnCu 2 Sn(S 0.95 Se 0.05 ) 4 , ZnCu 2 Sn(S 0.90 Se 0.10 ) 4 , ZnCu 2 Sn(S 0.85 Se 0.15 ) 4 , ZnCu 2 Sn(S 0.80 Se 0.20 ) 4 , and ZnCu 2 Sn(S 0.75 Se 0.25 ) 4 . The introduction of selenium into the ZCTS matrix enables the selective tuning of the bandgap, favoring light absorption and enhancing photocatalytic activity through visible light. From the several compositions examined, ZnCu 2 Sn(S 0.75 Se 0.25 ) 4 was identified as the best catalyst, with higher adsorption efficiency for pollutants (especially SO 2 and CO 2 ) and better ease of movement for charge carriers due to its low effective electron (hole) mass. In the meantime, selenium replacement not only enhanced the adsorption intensity but also improved the mechanical stability and thermodynamic properties of Se-doped catalysts, providing stable performance for long-term operation. This work not only emphasizes the potential of ZnCu 2 Sn(S 1-x Se x ) 4 as an environmentally friendly solution for multi-pollutant remediation, but also provides a pathway to tune newly designed material properties towards widespread and sustainable industrial applications. The results offer an advanced future in which engineered materials will help to clean the environment by storing toxic waste products.