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Research news from our group





Review article in the prestigious journal Progr. Mater. Sci.:


P. KumarA. PournaraK.-H. KimV. BansalS. RaptiM. J. Manos, “Metal-organic frameworks: Challenges and opportunities for ion-exchange/sorption applications”, Prog. Mater. Sci. 2017, 86, 25.



Exposure to common ionic pollutants, such as heavy metal ions and toxic anions, is a major concern throughout the world due to their potential impacts on human health and the environment. Recently, metal-organic frameworks (MOFs) with ion-exchange properties have attracted great interest with respect to the capture of diverse hazardous cationic and anionic species. In fact, according to the investigations on these ion exchangers, their sorption capacities are recognized to be considerably superior to conventional materials. This review focused on metal-organic materials as sorbents for ions by surveying MOFs with respect to their exchange/sorption capacities in association with their synthesis and structural characteristics. We also described the recent development in MOF composites and their practical applications toward wastewater treatment. The sorption characteristics were also evaluated among the reported MOFs and then between MOFs and other sorbents. Finally, we described the future prospects for the research and development in materials for ion-exchange based on MOF technology.

Invited article in the themed collection of Inorg. Chem. Front. in the honour of Prof. M. Kanatzidis:


E. Papazoi,   A. Douvali,   S. Rapti,  E. Skliri,   G. S. Armatas,  G. S. Papaefstathiou,   X. Wang,  Z.-F. Huang ,   S. Kaziannis,  C. Kosmidis,   A. Hatzidimitriou,  T. Lazarides, M. J. Manos   “A microporous Mg2+ MOF with cation exchange properties in a single-crystal-to-single-crystal fashion” Inorg. Chem. Front. 2017, 4, 530. 












We report here a new alkaline earth metal ion organic framework [Mg2(NH2BDC)2(HNO3)]∙9H2O (AEMOF-7), which shows a 3-D microporous structure with several unusual features, such as the rare trigonal prismatic coordination geometry of one of the crystallographically unique Mg2+ centers and the existence of a bridging HNO3 ligand. The H+ ions of the HNO3 ligand are dissosiable as demonstrated via proton conductivity measurements. AEMOF-7 displays relatively high selectivity for CO2 vs. CH4 and negliglibe N2 uptake. Interestingly, this compound was found capable for single-crystal-to-single-crystal (SCSC) exchange of Mg2+ by Cu2+ ions, first time observed in a MOF material. AEMOF-7 is also luminescent and its photophysical properties were investigated via solid state UV-Vis, steady-state and time-resolved luminescence studies.

The most efficient sorbent and sensor for Cr(VI) ever reported:


S. Rapti, D. Sarma,S. Diamantis, E. Skliri, G. S. Armatas, A. Tsipis, Y. S. Hassan, M. H. Alkordi, C. D. Malliakas, M. Kanatzidis, T. Lazarides*, J. C. Plakatouras*, M. J. Manos*, “All in one porous material:Exceptional sorption and selective sensing of hexavalent chromium by a Zr4+ MOF”, J. Mater. Chem. A, 2017, 5, 14707.



















We report a new microporous  metal-organic framework (MOF) H16[Zr6O16(H2PATP)4]Cl8∙xH2O (H2PATP =2-((pyridin-1-ium-2-ylmethyl)ammonio)terephthalate),  denoted as MOR-2 (metal organic resin-2).  MOR-2 represents the first Zr4+-terephthalate MOF with an 8-connected net and also the first example where a bulky functional group was intoduced into the terephalate scaffold prior the MOF synthesis. MOR-2 shows extraordinary capability to rapidly capture (within 1 min) hexavalent chromium with a sorption capacity up to 194 mg Cr(VI)/g, which far exceeds those reported for the known Cr(VI) sorbents. Moreover, MOR-2 in its composite form with alginic acid (HA) can be utilzed in ion exchange columns, which are highly efficient for removal of Cr(VI) from aqueous solutions including industrial waste samples and also can be regenerated and reused several times with minimal loss (<20%) of their capacity. Besides an excellent sorbent, MOR-2 is also a highly efficient sensor for  real time detectiion of Cr(VI) species as revealed by fluorescence titration experiments in acidic aqueous media. The Cr(VI) detection limits were found as low as 4  ppb, while the system exhibited excellent sensitivity when real world, instead of standard, samples were employed. Thus, MOR-2 material is a unique example combining both excellent sorption and exceptional luminescence sensing of Cr(VI) species in aqueous solutions.

Metal organic material first time used in ion exchange column for removal of organic dyes from water:


A. Pournara, S. Rapti, E. Skliri, G. S. Armatas, A. Tsipis, M. J. Manos*, “Highly efficient sorption of methyl orange by a metal organic resin-alginic acid composite”, ChemPlusChem 2017, 82, 1188  (Special issue: Early Career Series).


















The composite anion-exchange material MOR-1-HA (metal organic resin 1-alginic acid) was investigated as sorbent for the capture of the methyl orange anion (MO-) from aqueous solutions. MOR-1-HA shows a remarkably high sorption capacity (up to 859 mg/g) and very rapid sorption kinetics, the fastest among the reported metal organic sorbents. It shows capability to absorb MO- within a wide pH range (1-8) and in addition, it exhibits significant MO- sorption affinity even in the presence of large excess of competitive anions (Cl-, NO3 -, SO42- etc.). The exceptional MO- sorption properties of MOR-1-HA are due not only to its highly porous structure and easily exchangeable Cl- anions, but also to a multitude of interaction effects such as electrostatic interactions between MO- and NH3 +-functional groups of the material, hydration/dehydration, hydrophobicity/hydrophilicity, size and capacity of generating lateral interactions, and intercalation as revealed by theoretical studies. An ion exchange column with a stationary phase containing MOR-1-HA and silica sand showed high efficiency for the removal of MO- from various types of aqueous samples. The column can be easily regenerated and reused for many runs with minimal loss (2.3-9.3%) of its exchange capacity. The simplicity of MOR-1–HA/sand column and its high regeneration capability and reusability make it particularly attractive for application in the remediation of MO--contaminated industrial wastewater.

The most efficient TcO4-/ReO4- MOF sorbent reported and the demonstration of ReO4- luminescence sensing for MOF materials for the first time:

S. Rapti, S. A. Diamantis, A. Dafnomili, A. Pournara, E. Skliri, G. S. Armatas, A. C. Tsipis, I. Spanopoulos, C. D. Malliakas, M. G. Kanatzidis, J. C. Plakatouras*, F. Noli*, T. Lazarides*, M. J. Manos*, “Exceptional TcO4- sorption capacity and highly efficient ReO4- luminescence sensing by Zr4+ MOFs”, J. Mater. Chem. A, 2018, 6, 20813.



















The sorption properties of [Zr6O4(OH)4(NH3+-BDC)6]Cl6.xH2O (MOR-1) and H16[Zr6O16(H2PATP)4]Cl8.xH2O (MOR-2) towards ReO4- and TcO4- were studied in detail. Both MOR-1 and MOR-2 are very effective sorbents for ReO4- and TcO4- anions, with MOR-2 showing the highest sorption capacity (up to 4.1 mmol/g) among the known metal organic materials. Importantly, the exceptional sorption capacity of MOR-2 is retained even under conditions simulating acidic nuclear waste. In addition, MOR-1 and MOR-2 exhibit selective luminescence ReO4- sensing properties, demonstrated for the first time for MOF materials.

The first example of MOF capable of sorption and electrochemical sensing of heavy metal ions:

A. D. Pournara, A. Margariti, G. D. Tarlas, A. Kourtelaris, V. Petkov, C. Kokkinos, A. Economou, G. S. Papaefstathiou*, M. J. Manos*, “A Ca2+ MOF combining highly efficient sorption and capability for voltammetric determination of heavy metal ions in aqueous media”, J. Mater. Chem. A, 2019, 7, 15432.











We recently discovered that the Ca2+ two-dimensional framework, namely [Ca(H4L)(DMA)2]·2DMA (Ca-MOF) was capable of exchanging the Ca2+ ions by Cu2+ almost quantitatively in a matter of seconds in aqueous solution. Herein, we report that the Ca-MOF exhibits capability for both removal and voltammetric determination of heavy metal ions in aqueous media. Ca-MOF shows one of the highest Pb2+ sorption capacities (~522 mg g-1) reported for MOFs. More importantly, a column filled with Ca-MOF (1% wt.) particles dispersed in silica sand (99% wt.) can quantitatively remove traces of Pb2+ (~100 ppb) from a relatively large volume of a wastewater simulant solution (containing large excess of competitive ions). Ca-MOF is also highly efficient for sorption of Cd2+, Ni2+ and Zn2+, even in the presence of several competitive cations. Actually, the Cd2+ sorption capacity (~220 mg g-1) of Ca-MOF is one of the largest reported for MOFs. Furthermore, detailed Ni2+ and Zn2+ sorption studies of MOFs have not been described prior to this work.  The mechanism of the M2+ (M2+= Pb2+, Cd2+, Ni2+, Zn2+) exchange process was elucidated based on a series of spectroscopic, analytical and X-ray diffraction methods. In addition, a simple ready-to-use electrochemical sensor based on modified graphite paste with Ca-MOF was fabricated and successfully utilized for the determination of Pb2+, Cd2+, Cu2+ and Zn2+ at µg L-1 levels in aqueous solutions by anodic stripping voltammetry (ASV).  Overall, this work demonstrates, for the first time, a dual function of a MOF as a sorbent and as an electrochemical sensor for heavy metal ions, thus opening a new window for materials with appllication in both envirnomental remediation and monitoring.

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