Two-Photon Absorption and Fluorescence in Micrometer-Sized Single Crystals of a Rhodamine B Coordinated Metal–Organic Framework

A Rhodamine B (RhB) dye coordinated, 2D metal–organic framework (MOF), {[Zn2(L)­(RhB)]·5DMF}n (1; DMF = N,N-dimethylformamide), was constructed solvothermally from a −NH2-functionalized ligand and ZnII ions. The MOF features interlayer π···π interaction between the RhB molecules with an overlap of almost 100%. One- and two-photon-excited fluorescence measurements were carried out on micrometer-sized single crystals of varied thickness with continuous-wave and femtosecond pulsed lasers, respectively. The two-photon absorption coefficient was measured relative to the CdS crystal and found to be 7.1 ± 0.7 cm/GW at a wavelength of 1030 nm. Our findings demonstrate a new way of achieving solid-state dye microlasers or microsized light-frequency upconverters.