Here, we use surface-sensitive 2nd-order nonlinear Sum and Diference Frequency Generation Spectrocopies (SFG&DFG), to study the water vibrational dynamics during in situ photocatalytic water splitting. We initially photoexcite the samples and subsequently the SFG&DFG probes the interfacial dynamics of water molecules. The aim is to understand the processes undergone by interfacial water molecules during photocatalysis and connect them with the properties of novel photocatalytic materials, like the family of semiconducting Metal-Organic Frameworks (MOFs), as well as the overall efficiency of the process. For this project we are strongly collaborating with the group of Dr. Jose Sánchez Costa at IMDEA, synthetizing for us the MOF samples, as well as the group of Dr. Rosa Arán Ais in the University of Alicante, performing for us the photocatalytic water splitting efficiency measurements in operando.