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An alarming increase in the use of pesticides and organoarsenic compounds and their toxic impacts on the environment have inspired us to develop a selective and highly sensitive sensor for the detection of these pollutants. Herein, a bio-friendly, low-cost Al-based luminescent metal-organic framework ( 1' )-based fluorescent material is demonstrated that helps in sustaining water quality by rapid monitoring and quantification of a long-established pesticide (pendimethalin) and a widely employed organoarsenic feed additive (roxarsone). A pyridine-functionalized porous aluminum-based metal-organic framework (Al-MOF) was solvothermally synthesized. After activation, it was used for fast (<10 s) and selective turn-off detection of roxarsone and pendimethalin over other competitive analytes. This is the first MOF-based recyclable sensor for pendimethalin with a remarkably low limit of detection (LOD, 14.4 nM). Real-time effectiveness in detection of pendimethalin in various vegetable and food extracts was successfully verified. Moreover, the aqueous-phase recyclable detection of roxarsone with an ultralow detection limit (13.1 nM) makes it a potential candidate for real-time application. The detection limits for roxarsone and pendimethalin are lower than the existing luminescent material based sensors. Furthermore, the detection of roxarsone in different environmental water and a wide pH range with a good recovery percentage was demonstrated. In addition, a cheap and bio-friendly 1'@chitosan@paper strip composite was prepared and successfully employed for the hands-on detection of pendimethalin and roxarsone. The turn-off behavior of 1' in the presence of pendimethalin and roxarsone was examined systematically, and plausible mechanistic pathways were proposed with the help of multiple experimental evidences.

The metal-organic framework (MOF) Hf-DUT-52 was prepared with diamino functionality by the solvothermal method. This material displayed fluorometric sensing ability toward a nerve agent simulant (diethyl chlorophosphate (DCP)) and 3-diethylaminophenol (3-DEAP). It is the first-ever reported fluorescent MOF sensor for DCP and 3-DEAP. Apart from a fast response (<5 s), the sensor had a very low detection limit for both DCP and DEAP (limit of detection (LOD) values for DCP and 3-DEAP sensing were 9 and 125 nM, respectively). The obtained detection limit is the second lowest among all of the reported optical sensors for DCP. The sensor also displayed its capability to identify the presence of trace amount of DCP in various natural water specimens with good selectivity. Moreover, MOF@cotton composites were developed for visual, on-site, nanomolar-level detection of both targeted analytes. Furthermore, a MOF@PVA thin film was fabricated and successfully utilized for the detection of highly volatile and deadly poisonous DCP in the vapor phase. The sensor was also recyclable for up to five cycles without losing appreciable efficiency. Density functional theory (DFT)-based periodic and cluster calculations were performed to shed light on the sensing ability of the MOF by studying the interactions of DCP and DEAP with the MOF. Our theoretical results reveal the importance of linker defects and water chemisorption on the adsorption/complexation of the analytes at uncoordinated Hf sites.

Adsorbents able to uptake large amounts of gases within a narrow range of pressure, i.e. , phase-change adsorbents, are emerging as highly interesting systems to achieve excellent gas separation performances with little energy input for regeneration. A recently discovered phase-change metal-organic framework (MOF) adsorbent is F4&#95;MIL-140A(Ce), based on Ce IV and tetrafluoroterephthalate. This MOF displays a non-hysteretic step-shaped CO 2 adsorption isotherm, reaching saturation in conditions of temperature and pressure compatible with real life application in post-combustion carbon capture, biogas upgrading and acetylene purification. Such peculiar behaviour is responsible for the exceptional CO 2 /N 2 selectivity and reverse CO 2 /C 2 H 2 selectivity of F4&#95;MIL-140A(Ce). Here, we combine data obtained from a wide pool of characterisation techniques - namely gas sorption analysis, in situ infrared spectroscopy, in situ powder X-ray diffraction, in situ X-ray absorption spectroscopy, multinuclear solid state nuclear magnetic resonance spectroscopy and adsorption microcalorimetry - with periodic density functional theory simulations to provide evidence for the existence of a unique cooperative CO 2 adsorption mechanism in F4&#95;MIL-140A(Ce). Such mechanism involves the concerted rotation of perfluorinated aromatic rings when a threshold partial pressure of CO 2 is reached, opening the gate towards an adsorption site where CO 2 interacts with both open metal sites and the fluorine atoms of the linker., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

The novel Zr IV -based perfluorinated metal-organic framework (PF-MOF) [Zr 6 O 4 (OH) 4 ( TFS ) 6 ] ( ZrTFS ) was prepared under solvent-free conditions using the commercially available tetrafluorosuccinic acid ( H 2 TFS ) as a bridging ditopic linker. Since H 2 TFS can be seen as the fully aliphatic and perfluorinated C 4 analogue of fumaric acid, ZrTFS was found to be isoreticular to zirconium fumarate ( MOF-801 ). The structure of ZrTFS was solved and refined from X-ray powder diffraction data. Despite this analogy, the gas adsorption capacity of ZrTFS is much lower than that of MOF-801 ; in the former, the presence of bulky fluorine atoms causes a considerable window size reduction. To have PF-MOFs with more accessible porosity, postsynthetic exchange (PSE) reactions on (defective) MOF-801 suspended in H 2 TFS aqueous solutions were carried out. Despite the different H 2 TFS concentrations used in the PSE process, the exchanges yielded two mixed-linker materials of similar minimal formulae [Zr 6 O 4 (μ 3 -OH) 4 (μ 1 -OH) 2.08 (H 2 O) 2.08 ( FUM ) 4.04 ( HTFS ) 1.84 ] ( PF-MOF1 ) and [Zr 6 O 4 (μ 3 -OH) 4 (μ 1 -OH) 1.83 (H 2 O) 1.83 ( FUM ) 4.04 ( HTFS ) 2.09 ] ( PF-MOF2 ) ( FUM 2- = fumarate), where the perfluorinated linker was found to fully replace the capping acetate in the defective sites of pristine MOF-801 . CO 2 and N 2 adsorption isotherms collected on all samples reveal that both CO 2 thermodynamic affinity (isosteric heat of adsorption at zero coverage, Q st ) and CO 2 /N 2 adsorption selectivity increase with the amount of incorporated TFS 2- , reaching the maximum values of 30 kJ mol -1 and 41 (IAST), respectively, in PF-MOF2 . This confirms the beneficial effect coming from the introduction of fluorinated linkers in MOFs on their CO 2 adsorption ability. Finally, solid-state density functional theory calculations were carried out to cast light on the structural features and on the thermodynamics of CO 2 adsorption in MOF-801 and ZrTFS . Due to the difficulties in modeling a defective MOF, an intermediate structure containing both linkers in the framework was also designed. In this structure, the preferential CO 2 adsorption site is the tetrahedral pore in the "UiO-66-like" structure. The extra energy stabilization stems from a hydrogen bond interaction between CO 2 and a hydroxyl group on the inorganic cluster.