Enhanced Optical Nonlinearity in Highly Conjugated Triply Fused Porphyrin-Anchored Ti₃C₂T_x Nanosheets

Ultrafast interfacial charge transfer in functionalized two-dimensional semiconductors enables precise modulation of their optical and electronic properties. Herein, we report the axial integration of a triply fused porphyrin dimer (TFP) onto few-layer MXene (Ti₃C₂T_x) nanosheets via a stepwise covalent strategy comprising initial pyridine anchoring followed by metal-coordination-driven TFP assembly. Z-scan measurements conducted under nanosecond (532 nm) and femtosecond (800 nm) laser excitation both reveal significantly enhanced nonlinear optical absorption relative to the pristine constituents. This enhancement is mainly attributed to the photoinduced charge transfer from the TFP donor to the Ti₃C₂T_x acceptor matrix, as corroborated by steady-state and transient absorption spectroscopy in conjunction with theoretical calculations. Beyond the demonstration of a high-performance optical limiter, this work establishes a molecular-level design paradigm for engineering interfacial electronic coupling in hybrid two-dimensional architectures subjected to intense optical fields.