A Water-Stable Cationic Metal–Organic Framework with Hydrophobic Pore Surfaces as an Efficient Scavenger of Oxo-Anion Pollutants from Water

Abstract

Water contamination due to heavy metal-based toxic oxo-anions (such as CrO4 2– and TcO4 –) is a critical environmental concern that demands immediate mitigation. Herein, we present an effort to counter this issue by a novel chemically stable cationic metal–organic framework (iMOF-2C) with strategic utilization of a ligand with hydrophobic core, known to facilitate such oxo-anion capture process. Moreover, the compound exhibited very fast sieving kinetics for such oxo-anions and a very high uptake capacity for CrO4 2– (476.3 mg g–1) and ReO4 – (691 mg g–1), while the latter being employed as a surrogate analogue for radioactive TcO4 – anions. Notably, the compound showed excellent selectivity even in the presence of other competing anions such as NO3 –, Cl–, SO4 2–, ClO4 –. etc.. Furthermore, the compound possesses excellent reusability (up to 10 cycles) and is also employed to a stationary phase ion column to decontaminate the aforementioned oxo-anions from water.

Recognition and Sequestration of Toxic Inorganic Water Pollutants with Hydrolytically Stable Metal‐Organic Frameworks

“…With experience gathered from our previous works we have tried to improve upon the issues faced in order to design a better suited sorbent material by strategic choice of a benzene centered tripodal organic linker (L=1,1′‐(5′‐(4‐(1H‐imidazol‐1‐yl)phenyl)‐[1,1′:3′,1′′‐terphenyl]‐4,4′′‐diyl)bis(1H‐imidazole)) (Figure 9). [86] Assembled with Ni 2+ as the metal node iMOF‐2C [{Ni(L) 2 } ⋅ (SO 4 ) ⋅ x(G)] n (L=ligand); G=DMF, H 2 O) is 2D cationic with free tetrahrdral SO 4 2− anions to balance out the framework charge. A closer look at the structural features of this MOF reveals octahedral coordination around the Ni 2+ center coming from six independent imidazole N atoms creating steric crowding that acts as shield rendering enhanced chemical stability.…”

Functionalized Ionic Porous Organic Polymers Exhibiting High Iodine Uptake from Both the Vapor and Aqueous Medium

“…Furthermore, we probed the selectivity of i POPs for I 3 – capture to get an idea regarding the applicability of the solid adsorbent in real-time. Typically, contaminated water contains several counter anions, including chloride (Cl – ), bromide (Br – ), nitrate (NO 3 – ), and sulphate (SO 4 2– ), which may cause hindrance in the uptake of I 3 – by i POPs . To check this, the capture of I 3 – was investigated from a binary mixture of anions (equimolar solution of I 3 – and other competing ions viz.…”

“…At first, we prepared 1,1′-(5′-(4-(1 H -Imidazol-1-yl)­phenyl)-[1,1′:3′,1″-terphenyl]-4,4″-diyl)­bis­(1 H -imidazole) (ligand 1) as per the literature protocol . Furthermore, compound-1 was synthesized via invoking a reported protocol with slight modification .…”

“…At first, we prepared 1,1′-(5′-(4-(1H-Imidazol-1-yl)phenyl)-[1,1′:3′,1″-terphenyl]-4,4″-diyl)bis(1H-imidazole) (ligand 1) as per the literature protocol. 43 Furthermore, compound-1 was synthesized via invoking a reported protocol with slight modification. 44 1,1′-(5′-(4-(1H-Imidazol-1-yl)phenyl)-[1,1′,3′,1″-terphenyl]-4,4″-diyl)bis(1H-imidazole) (0.3986 mmol, 201 mg) was reacted with 1,4-bis-bromomethyl-benzene (0.7955 mmol, 210 mg) in 20 mL N,N-dimethylformamide (DMF) at 100 °C for 24 h. After cooling this mixture to room temperature, 1 mL benzyl bromide was added, and the reaction mixture was further heated at 80 °C for 12 h. The solid crude product obtained was collected and thoroughly washed with different solvents viz.…”

Neutral Nitrogen Donor Ligand‐based MOFs for Sensing Applications

“…Accordingly, an expansive library of thousands of MOF structures (∼99,000) has been uncovered since their discovery in the late 20 th century, as per the latest CSD study [14] . The myriad possibilities for network tailoring in MOFs have resulted in potential application in diverse fields, including molecular sensing, pollutant capture, clean energy, heterogeneous catalysis, gas separation, conductivity, and drug delivery [15–32] …”