Recent developments in NO_x capture and conversion using nano-structured materials: A comprehensive review

Controlling emissions of nitrogen oxides () from stationary and mobile sources is an area of increasing interest due to their significant environmental and health impact. This control can be in the form of converting to the benign N₂ or to valuable chemicals such as NH₃ and HNO₃. Several conversion methods exist to accomplish this goal, including Selective Catalytic Reduction (SCR), photocatalysis methods, the electrochemical pathway, etc. Additionally, capture and storage can serve as a means for directly mitigating emissions or as a enrichment process for downstream conversion. In both conversion and storage processes, nano-structured materials achieve high de- performance. These materials include the traditional transition metal oxides, MOFs, the novel MXenes, and many other classes. The present review paper provides an overview of these materials, outlines their use cases, highlights their strengths and drawbacks, and delineates the operating conditions in which each excels. Additionally, this work identifies existing trends and future research opportunities to enhance control using nano-structured materials. These trends include safety enhancements through phasing-out toxic substances, an expansion of adsorption operating windows to low temperatures and concentrations, and economic improvements with novel non-precious metals adsorbers as well as improved poison resistance.