Anastasia Pournara

Rapid, green and inexpensive synthesis of high quality UiO-66 amino-functionalized materials with exceptional capability for removal of hexavalent chromium from industrial waste

We describe a new synthetic method for the isolation of the UiO-66 amino-functionalized material (called metal organic resin-1, MOR-1) and its composite with alginic acid (HA). MOR-1 can be prepared in high yield (∼70%) and purity within an hour via a reflux reaction of ZrCl4 and 2-amino-terephthalic acid in acifidied aqueous solution, whereas addition of sodium alginate to the fine suspension of MOR-1 resulting from the reflux synthesis affords the MOR-1-HA composite. This inexpensive, green and fast preparation method results in UiO-66 amino-functionalized materials (MOR-1 and MOR-1-HA) of the same quality and microporous features as those of compounds isolated with the slower solvothermal synthesis involving toxic and costly organic solvents. Field Emission-Scanning Electron Microscopy (FE-SEM) studies revealed that MOR-1 consists of spongy nanoparticles (150–300 nm in size), whereas MOR-1-HA nanoparticles are relatively compact. Thus, for the first time we could visualize the effect of alginic acid partially coating the surface of the MOR particles. The composite prepared by this method can be successfully utilized as a stationary phase, mixed with sand, in an anion-exchange column. The column shows excellent hexavalent chromium sorption properties and can be easily regenerated and reused several times with almost no loss of its initial Cr(VI) removal capacity. Remarkably, this ion exchange column is capable of eliminating Cr(VI) ions from chrome plating wastewater samples, thus indicating its potential for applications in industrial wastewater treatment.

Luminescent metal–organic frameworks as chemical sensors: common pitfalls and proposed best practices

The ever-increasing need to determine and monitor the chemical constituents of the constantly evolving environment has led the global scientific community to invest considerable research effort in the development of efficient and user-friendly chemical sensors. The development of improved chemical sensors largely depends on the synthesis of novel materials with the ability to transform a molecular recognition event into a readable signal. Among the various types of sensory materials, those where analyte detection is based on the change of a luminescence signal are gaining increasing attention due to the extremely high sensitivities which can be achieved in combination with new technological advances enabling the integration of optical detection systems in small, portable and easy to use devices. In this critical review we approach the emerging field of sensory materials based on luminescent metal–organic frameworks (LMOFs) by beginning with a survey of the general principles of luminescence-based sensing. In particular, after a brief overview, we first focus on the working principles and successes of well established sensory materials based on small molecules and conjugated polymers. Subsequently, we concentrate on the special features of LMOFs which make them promising sensory materials and we discuss best practices which researchers in the field should follow in order to prove the sensing ability of LMOFs and avoid common misconceptions and errors. We continue with presenting selected examples of LMOF-based sensors for nitroaromatics, humidity and heavy metal ions from the recent literature and we conclude with a summary of the state-of-the-art of LMOF sensors. Finally, we propose some directions for future research on LMOF sensors.

Exceptional TcO4− sorption capacity and highly efficient ReO4− luminescence sensing by Zr4+ MOFs

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 ± 0.4 mmol g−1) 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.

Correction: Selective capture of hexavalent chromium from an anion-exchange column of metal organic resin-alginic acid (Chem. Sci. (2016) DOI: 10.1039/c5sc03732hcomposite)

Correction for ‘Selective capture of hexavalent chromium from an anion-exchange column of metal organic resin–alginic acid composite’ by Sofia Rapti et al., Chem. Sci., 2016, DOI: 10.1039/c5sc03732h.