Tunable Nonlinear Optical Properties Based on Metal-Organic Framework Single Crystals

Solid-state hybrid materials with designability in topology and tunable photo-responsiveness hold great promise for multitudinous applications from optoelectronics to information storage/communication. However, the judicious design and synthesis of metal-organic frameworks (MOFs) with intrinsically custom-made nonlinear optical (NLO) properties including multiple photon absorption and harmonic generation effects suitable for miniaturized devices remain highly challenging. Herein, the design and synthesis of a novel pillared framework named after Zn-TCPE-DPNI MOF coordinated by zinc ions (Zn2+), aggregation induced emission (AIE) featured [1,1 '-biphenyl]-4-carboxylic acid (H4TCPE), and N,N '-di(4-pyridyl)-1,4,5,8-naphthalenetetracarboxydiimide (DPNI) are reported. The highly ordered Zn-TCPE-DPNI MOF single crystal exhibits tunable NLO responses by switching incident excitation wavelengths of a femtosecond laser from 900 to 1500 nm. The noticeable transformation from two- or three-photon excited photoluminescence (2PL or 3PL) to the concurrent occurrence of 3PL and third harmonic generation (THG), and eventually to the mere emergence of THG with a high effective susceptibility chi(3) (3 omega) of 2.9 x 10-12 esu is observed. This study paves a novel avenue for the design and synthesis of photoluminescent MOF crystals with tunable NLO responses toward the fabrication of multifunctional NLO devices targeted for optoelectronics and information communication. The design and synthesis of Zn-TCPE-DPNI MOF single crystals exhibiting tunable NLO responses is presented. Noticeable transformation from two- or three-photon excited photoluminescence (2PL or 3PL) to the concurrent occurrence of 3PL and third harmonic generation (THG), and eventually to the mere emergence of THG with a high effective susceptibility chi(3) (3 omega) of 2.9 x 10-12 esu is observed.image