Nonlinear Metal-Organic Framework Crystals for Efficient Multicolor Coherent Optical Emission

Non-centrosymmetric metal-organic frameworks (MOFs) have recently emerged as a promising class of coordination polymers for nonlinear optics and light conversion. Nevertheless, achieving high endurance and efficiency for the light conversion within the whole visible range by a single crystal of MOF remains a challenge. This article reports on the design of two non-centrosymmetric MOFs based on a 1,3,5-benzenetricarboxylic acid ligand and Er/Co ions, providing an efficient and simultaneous multiple second and third optical harmonic generations (SHG, THG) from 400 to 750 nm with a high endurance (over 100 cycles or 3 h of continuous operation). Optical experiments and quantum chemical modeling of the MOF single crystals confirm the polarization and chemistry-dependent efficiency of SHG and THG, associated with the varied MOFs' symmetry and dipole moment. The observed coherent light conversion within the whole visible range by MOF single crystals at ambient conditions makes it possible to achieve the multicolor (up to three) coherent emission required for modern laser technologies, making MOFs highly competitive and sustainable materials for nonlinear optics.