We report the first one-dimensional tubular metal-organic framework (MOF) [Ni(Cu-H6TPPA)]∙2DMA (H8TPPA = 5,10,15,20-tetrakis[p-phenylphosphonic acid] porphyrin) in the literature. The structure of this MOF, known as GTUB4, was solved using single crystal X-ray diffraction and its surface area was calculated to be 1102 m2/g, making it the phosphonate MOF with the highest reported surface area. GTUB4 also possesses a narrow indirect band gap of 1.9 eV and a direct band gap of 2.16 eV, making it a semiconducting MOF. Thermogravimetric analysis of GTUB4 suggests that it is thermally stable up to 400°C. Owing to its high surface area, low band gap, and thermal stability, GTUB4 could find applications as electrodes in supercapacitors.