NIR‐II Emitted Er(III) Coordination Polymers with P‐Nitrobenzoic Acid

{[Er(NBA) 3 (H 2 O) 3 ].2DMF} n coordination polymers (Er‐NBA, NBA = 4‐nitrobenzoic acid, DMF = N,N‐dimethylformamide) are synthesized by hydrothermal methods, and the corresponding crystal structures and photoluminescence properties are systemically studied. Er‐NBA coordination polymers exhibit 1D chain structures, which are formed by linking the adjacent Er 3+ ions using bidentate bridging carboxylate groups of the NBA ligands and show superior thermal stability below 400 °C. Under the characteristic excitation of NBA ligand, Er‐NBA coordination polymers show the characteristic near infrared II (NIR‐II) emission at 1532 nm of Er 3+ owing to the efficient NBA → Er 3+ energy transfer process. The results provided significant theoretical support for developing NIR‐II emitted lanthanide coordination polymers.