Metal organic framework as “turn-on” fluorescent sensor for Zr(IV) ions and selective adsorbent for organic dyes

A new cobalt-based mixed ligand metal–organic framework (MOF), [Co2(L1)(obc)2].DMF (MOF1), (where L1 = 2,7-bis (3-(1H-imidazole-1-yl)propyl)benzo-[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone and H2obc = 4,4-oxybisbenzoic acid) was prepared solvothermally that simultaneously exhibits sensing and adsorption capability. The single-crystal X-ray structural analysis revealed that MOF1 exhibits an interpenetrated three-dimensional framework, of pcu topology, comprising classic paddlewheel-type units. The synthesized MOF1 was found to be luminescent with an emission/excitation peak at 402/275 nm that is enhanced by Zr4+ ions due to absorbance-caused enhancement (ACE). The fluorescence studies displayed the highly selective and sensitive behavior of MOF1 towards Zr4+ ions through the turn-on fluorescence effect with a short response time and detection limit of 0.067 μM. Furthermore, MOF1 was successfully applied for the treatment of commercial dyes Reactive Black 5 and Orange G with adsorption capacity of 33.79 and 22.32 mg/g, respectively, thus showing rapid adsorption for these dyes.