You can do FTIR analysis, but remember that FTIR generally do not recognize metals specifically as metal peaks appear below 600 cm-1. Here you can explain it through oxygen bond as changes occur before and after hydrothermal treatment. it could useful and beneficial while publishing a paper as well. You have to consider all the aspects. To further understand metal interaction with surface entities through FTIR, consult to the following paper; https://www.nature.com/articles/s41598-023-33902-9