Phthalocyanine-Based 2D Polymer for Ultrafast Nonlinear Optical Application

Strong ultrafast nonlinear optical (NLO) responses in near-infrared (NIR) regions and favorable solution processability are two urgent requirements for practical NLO applications, especially for optical limiting (OL) applications. However, simultaneously optimizing these properties remains significant challenging. In this study, the successful synthesis of a phthalocyanine-based 2D polymer (Pc-2DP) is reported; its structure features extended π-electrons delocalization space constructed by topologically integrating the phthalocyanine units into the 2D framework. The as-prepared few-layered Pc-2DP not only exhibits power- and wavelength-dependent NLO properties toward 35 fs ultrafast pulsed laser, but it also demonstrates excellent ultrafast reverse saturable absorption (RSA) responses in NIR regions. The nonlinear absorption coefficients of Pc-2DP dispersion reach up to 0.12 and 0.19 cm GW⁻¹ at 800 and 1550 nm, respectively, which are much higher than those of the typical MXene (Ti₃C₂T_X) and molybdenum disulfide with hexagonal structure (2H-MoS₂). The obtained NLO devices exhibit remarkable OL performance at 800 nm and, particularly, in the telecommunication region (1300 to 1550 nm), which is highly desired but seldom reported. The study demonstrates that the as-prepared Pc-2DP featuring a highly conjugated aromatic framework is a very promising OL material and that this research provides a new strategy for developing high-performance 2D organic NLO polymers.