Covalent Functionalization of MXenes with Porphyrin for Visible-Light Activation in Energy Conversion Nanodevices

MXenes such as Ti₃C₂ and Ti₃CN are 2D materials characterized by the presence of a T_x phase that passivates the reactive titanium surface. Modifying their chemical composition to anchor target molecules is of great interest for addressing key challenges, such as enhancing the conversion of visible light into electricity. In this study, a covalent functionalization strategy is developed to modify the T_x phase of Ti₃C₂ or Ti₃CN with alkyl amines, followed by coupling with Zn-porphyrin. This process activates the optical properties of MXenes without causing any damage. X-ray photoelectron spectroscopy and infrared spectroscopy are pivotal in confirming the covalent functionalization, while thermogravimetric analysis, transmission electron microscopy, and additional techniques provided further insights into structural and chemical features. Spectroelectrochemical investigations reveal carrier injection into MXenes under light illumination, potentially enhancing conductivity. Photodetectors fabricated from these films demonstrate responsivities of 1.4-15.0 A W^-1 and external quantum efficiencies ranging from 1300 to 2830% in the visible range, making them comparable to well-established hybrid 2D nanomaterials like MoS₂ and WS₂.