Many factories in the United States use materials called catalysts to speed up chemical reactions to make fuels, plastics, and other everyday products. A major cost in these manufacturing processes is managing heat inside chemical reactors. Some reactions require heat to occur, but others release heat. The heat that is produced is often wasted instead of being reused. This project will study how heat moves inside chemical reactors so that heat produced by one reaction can be used to power another reaction, making the process more efficient and lowering costs. The project will use special nanoparticles to develop better ways to measure temperature inside reactors, which can vary greatly in large systems filled with catalysts. The project will also help train students in catalysis and energy science and will include a hands-on activity that teaches high school students how heat-producing and heat-absorbing reactions can work together. This project will establish a mechanistic understanding and transferable design principles for thermally coupling tandem catalytic reactions to reduce external heating requirements. To investigate thermal coupling at the micro- and nanoscale, the project will study the exothermic reaction of CO methanation as a localized heat source to drive the endothermic reverse water–gas shift (RWGS) reaction for CO₂ conversion to CO. The research will have three aims: (1) identifying catalysts that selectively promote RWGS and CO methanation on distinct active sites; (2) elucidating the mechanistic linkages that govern their thermal coupling; and (3) tuning reaction parameters, including catalyst intimacy, bed composition, and reactant partial pressures, to precisely control heat flow while minimizing undesired byproducts. A key innovation is the use of in situ microthermometry based on photoluminescent upconverting nanoparticles (UCNPs), which enable spatially resolved measurements of local thermal gradients within the catalyst bed and quantif