Synthesis, Structure and Optical Studies of a Family of Three‐Dimensional Rare‐Earth Aminoisophthalates [M(μ 2 ‐OH)(C 8 H 5 NO 4 )] (M = Y 3+ , La 3+ , Pr 3+ , Nd 3+ , Sm 3+ , Eu 3+ , Gd 3+ , Dy 3+ , and Er 3+ )

A hydrothermal reaction of the acetate salts of the rare‐earths, 5‐aminoisophthalic acid (H 2 AIP), and NaOH at 150 °C for 3 days gave rise to a new family of three‐dimensional rare‐earth aminoisophthalates, [M(μ 2 ‐OH)(C 8 H 5 NO 4 )] [M = Y 3+ ( I ), La 3+ ( II ), Pr 3+ ( III ), Nd 3+ ( IV ), Sm 3+ ( V ), Eu 3+ ( VI ), Gd 3+ ( VII ), Dy 3+ ( VIII ), and Er 3+ ( IX )]. The structures contain M–O(H)–M chains connected by AIP anions. The AIP ions are connected to five metal centers and each metal center is connected with five AIP anions giving rise to a unique (5,5) net. To the best of our knowledge, this is the first observation of a (5,5) net in metal‐organic frameworks that involve rare‐earth elements. The doping of Eu 3+ /Tb 3+ ions in place of Y 3+ /La 3+ in the parent structures gave rise to characteristic metal‐centered emission (red = Eu 3+ , green = Tb 3+ ). Life‐time studies indicated that the excited emission states in the case of Eu 3+ (4 mol‐% doped) are in the range 0.287–0.490 ms and for Tb 3+ (4 mol‐% doped) are in the range of 1.265–1.702 ms. The Nd 3+ ‐containing compound exhibits up‐conversion behavior based on two‐photon absorption when excited using λ = 580 nm.