A proton-transfer complex of 1,2,4, 5-benzenetetracarboxylic acid ( H4 BTC ) with 1,10-phenanthroline ( phen ), [ ( H2 BTC )2-· 2 ( Hphen ) + · ( H4 BTC ) ] was synthesized and characterized by IR, UV-Vis spectra and luminescence. The structure was determined by X-ray single crystal diffraction. It crystallizes inthe triclinic system, space group P-1 with a = 7.3767(15), b = 10.704(2), c = 12.890(3)A, α = 102.96(3) ,β = 105.71(3), γ= 99.68(3)°, V = 926.0(3)A3, Dc = 1. 558 g/cm3, Z = 2, μ ( Mo-Kα ) = 0.121 mm-1 and F(000) = 448. Thefinal R = 0.0401 and wR = 0.0862 for 2983 observe reflections with [ 1 ＞ 2σ(1) ]. It is composed ofdiscrete H4BTC molecules, H2 BTC2- anions and [ Hphen] + cations. The extensive hydrogen-bonding associations formed between the H4 BTC molecules and H2 BTC2- anions result in the formation of a two-dimensional layer, to which the [ Hphen ] + cations are attached through the hydrogen bonds formed between the carboxyl groups of H4 BTC and the NH groups of [ Hphen ] + . Under the excitation of UV light, it emits an intense blue luminescence.