A new [Ca(H2O)6]2+ cations‐templated coordination polymer, namely {[Ca(H2O)6][Cu4(btec)2(μ3‐OH)2]}n (1, H4btec=1,2,4,5‐benzenetetracarboxylic acid), has been prepared via the solvothermal reactions of CuCl2 ⋅ 2H2O, CaCl2, and H4btec. X‐ray structural analysis revealed that it features a tetranuclear [Cu4(COO)6(μ3‐OH)2] cluster‐based 3D anionic framework with (4,8)‐connected scu topology that was further balanced by the isolated [Ca(H2O)6]2+ cations. The framework of 1 shows high thermostability under air atmosphere. Moreover, such compound shows high photocatalytic activity for the degradation of methyl blue (MB) with the degradation efficiency of 94.5 %, and the possible photocatalytic mechanism was also clarified.