A Multifunctional Mn^II Phosphonate for Rapid Separation of Methyl Orange and Electron‐Transfer Photochromism

Abstract

A Mn(II) phosphonate of the general formula [Mn(H2 L)2 (H2 O)2 (H2 bibp)] adopts a layered motif with protonated H2 bibp(2+) cations embedded in the channels (H4 L=thiophene-2-phosphonic acid; bibp=4,4'-bis(1-imidazolyl)biphenyl). The title compound exhibits excellent adsorptive removal of methyl orange (MO) dye from aqueous solution. Its advantageous features include fast adsorption, high uptake capacity, selective removal, and reusability, which are of great significance for practical application in wastewater treatment. Meanwhile, the compound displays rapid photochromism upon irradiation with visible light at room temperature. Extensive research has demonstrated that such behavior is based on a ligand-to-ligand charge-transfer (LLCT) mechanism. The irradiated sample possesses an ultra-long-lived charge-separated state. Moreover, not only is the compound the first Mn-based photochromic MOF, but it is also one of the very few examples showing LLCT with non-photochromic components.

Optically actuating ultra-stable radicals in a large π-conjugated ligand constructed photochromic complex

“…This phenomenon should be due to the generation of free radicals. Interestingly, no visible color bleaching was observed for QDU-12A even after thermal annealing at 290°C, different from the common photochromic complexes with easy discoloration by heating, but still similar with other rarely reported works [19]. Solid-state UV-vis diffuse-reflectance spectra could give more information about the photochromic phenomenon.…”

“…are substituted to the radical centers, also importantly influence the stabilization of generated radicals [17]. Moreover, intermolecular interactions could form condensed coordination networks, further preventing the contact of the generated radicals with oxygen at ambient conditions [18,19].…”

Base-Resistant Ionic Metal-Organic Framework as a Porous Ion-Exchange Sorbent

“…Thus the development of newer sorbents that can overcome the bottlenecks of existing/conventional adsorbents such as poor selectivity, slow kinetics, and stability are desired. Notably, majority of the studies using i-MOFs as sorbent of dyes have been performed in organic solvents or water at neutral pH ( Nickerl et al., 2013 , Zhao et al., 2013 , Zhao et al., 2017 , Chen et al., 2015 , Song et al., 2015 , Gao et al., 2016 , Yu et al., 2016 , Jia et al., 2016 , Li et al., 2017b , Li et al., 2017c , Nath et al., 2017 ). Dyes released as industrial wastewaters can have varying pH, and hence the stability and investigation of MOF-based adsorption at varying pH is more pertinent for seeking real-time applicability.…”

“…To extend this behavior even further, we checked the efficacy of IPM-MOF-201 to entrap anionic dyes of similar sizes, viz., indigo carmine (IC) and alizarin red S (ARS). It has been observed in the literature that the dye molecules with dimensions between the minimum and maximum pore windows in porous frameworks can undergo ion exchange ( Nickerl et al., 2013 , Zhao et al., 2013 , Zhao et al., 2017 , Chen et al., 2015 , Song et al., 2015 , Gao et al., 2016 , Yu et al., 2016 , Jia et al., 2016 , Li et al., 2017b , Li et al., 2017c , Nath et al., 2017 ). Thus linear ions having suitable dimensions can be expected to undergo uptake.…”

Efficient Capture of Organic Dyes and Crystallographic Snapshots by a Highly Crystalline Amino‐Acid‐Derived Metal–Organic Framework

“…Indeed, a good number of MOFs show efficient, and sometimes selective, adsorption and/or degradation through AOPs of both inorganic and organic contaminants . In particular, the use of MOFs for the elimination of organic dyes from water has been explored, and several examples of MOFs that can degrade dyes by means of AOPs have been reported, as well as water‐resistant functional MOFs capable of capturing anionic and/or cationic organic dyes, sometimes in a selective manner, from water …”