Synthesis of JUC-557. A solution of BCTB-4CHO (37.4 mg, 0.05 mmol 1.0 equiv.) and PDAN (31.2 mg, 0.1 mmol 1.0 equiv.) in dioxane (1.0 mL) containing NaOH (4 M, 0.1 mL) was degassed in a glass tube using three freeze/pump/thaw cycles. The tube was sealed off by flame and heated at 120 °C for 5 days. After cooling to room temperature, the tube was opened and the precipitate was filtered off and washed with acetone (extracted with Soxhlet). The solid was dried under vacuum at 100 °C overnight to afford the JUC-557 as a yellow powder (48.7 mg, yield 71%). Solid-state Synthesis of JUC-557-nanosheet. JUC-557 (100.0 mg) was dispersed into the methanol (200.0 mL), sonicated for 10 h, and took out the supernatant after centrifugation. The obtained supernatant was sonicated for 2 h and took out the supernatant after centrifugation again. Then, ultrathin JUC-557nanosheet was dried by a vacuum. Solid-state Fluorescence recognition. The titration experiments were conducted in a 3 mL standard quartz reactor equipped with the excitation wavelength of 352 nm. Typically, JUC-557 or JUC-557-nanosheet (180.0 µg) was dispersed in 3.0 mL of water/EtOH (v: v = 9: 1) solution with different analytes. The concentrations of cation and anion ions, I 2 , and aromatic nitro compounds were 1.0 × 10 -2 M, 5 × 10 -3 M, and 5 × 10 -4 M, respectively.