Nonlinear optical limiting effect and charge transfer dynamics in a Fe-porphyrin metal-organic framework

The nonlinear absorption effect in a Fe-porphyrin metal-organic framework (Co-TCPP(Fe) MOF) was studied using the nanosecond Z-scan technique, which showed an enhanced reverse saturation absorption (RSA) compared with TCPP(Fe) ligand. By femtosecond transient absorption (fs-TA) measurements, the charge transfer dynamics of MOF are unveiled. Compared with TCPP(Fe) ligand, the ultrafast formation of charge separation states (CSSs) with extra-long lifetime (> 3.5 ns) detracts the recombination of electron-hole pairs, resulting in an enhanced excited state absorption (ESA). Based on the strong ESA caused by CSSs absorption, the MOF nanosheets showed an excellent optical limiting (OL) effect with the OL threshold of 0.89 J/cm 2 .