A copper(I) 3,5-diphenyltriazolate metal-organic framework (CuTz-1) was synthesized and extensively characterized by using a multi-technique approach. The combined results provided solid evidence that CuTz-1 features an unprecedented Cu tz cluster as the secondary building unit (SBU) with channels approximately 8.3 Å in diameter. This metal-organic framework (MOF) material, which is both thermally and chemically (basic and acidic) stable, exhibited semiconductivity and high photocatalytic activity towards the degradation of dyes in the presence of H O . Its catalytic performance was superior to that of reported MOFs and comparable to some composites, which has been attributed to its high efficiency in generating OH, the most active species for the degradation of dyes. It is suggested that the photogenerated holes are trapped by Cu , which yields Cu , the latter of which behaves as a catalyst for a Fenton-like reaction to produce an excess amount of OH in addition to that formed through the scavenging of photogenerated electrons by H O . Furthermore, it was shown that a dye mixture (methyl orange, methyl blue, methylene blue, and rhodamine B) could be totally decolorized by using CuTz-1 as a photocatalyst in the presence of H O under the irradiation of a Xe lamp or natural sunlight.