Solvent-assisted ligand incorporation (SALI) of the ditopic linker 5-carboxy-3-(4-carboxybenzyl)thiazolium bromide [(H 2 PhTz)Br] into the zirconium metal−organic framework NU-1000 [Zr 6 O 4 (OH) 8 (H 2 O) 4 (TBAPy) 2 , where NU = Northwestern University and H 4 TBAPy = 1,3,6,8-tetrakis(p-benzoic-acid)pyrene], led to the SALIed NU-1000-PhTz material of minimal formula [Zr 6 O 4 (OH) 6 (H 2 O) 2 (TBAPy) 2 (PhTz)]Br. NU-1000-PhTz has been thoroughly characterized in the solid state. As confirmed by powder X-ray diffraction, this material keeps the same three-dimensional architecture of NU-1000 and the dicarboxylic extra linker bridges adjacent [Zr 6 ] nodes ca. 8 Å far apart along the crystallographic c-axis. The functionalized MOF has a BET specific surface area of 1560 m 2 /g, and it is featured by a slightly higher thermal stability than its parent material (T dec = 820 vs. 800 K, respectively). NU-1000-PhTz has been exploited for the capture and separation of two pollutant gases: carbon dioxide (CO 2 ) and nitrous oxide (N 2 O). The high thermodynamic affinity for both gases [isosteric heat of adsorption (Q st ) = 25 and 27 kJ mol −1 for CO 2 and N 2 O, respectively] reasonably stems from the strong interactions between these (polar) "stick-like" molecules and the ionic framework. Intriguingly, NU-1000-PhTz shows an unprecedented temperature-dependent adsorption capacity, loading more N 2 O in the 298 K ≤ T ≤ 313 K range but more CO 2 at temperatures falling out of this range. Grand canonical Monte Carlo simulations of the adsorption isotherms confirmed that the preferential adsorption sites of both gases are the triangular channels (micropores) in close proximity to the polar pillar. While CO 2 interacts with the thiazolium ring in an "end-on" fashion through its O atoms, N 2 O adopts a "side-on" configuration through its three atoms simultaneously. These findings open new horizons in the discovery of functional materials that may discriminate between polluting gases through selective adsorption at different temperatures.

Mercury is one of the most toxic heavy metals. By virtue of its triple bond, the novel ligand 1,2-bis(1H-pyrazol-4-yl)ethyne (H2BPE) was expressly designed and synthesized to devise metal–organic frameworks (MOFs) exhibiting high chemical affinity for mercury. Two MOFs, Zn(BPE) and Zn(BPE)·nDMF [interpenetrated i-Zn and noninterpenetrated ni-Zn·S, respectively; DMF = dimethylformamide], were isolated as microcrystalline powders. While i-Zn is stable in water for at least 15 days, its suspension in HgCl2 aqueous solutions prompts its conversion into HgCl2@ni-Zn. A multitechnique approach allowed us to shed light onto the observed HgCl2-triggered i-Zn-to-HgCl2@ni-Zn transformation at the molecular level. Density functional theory calculations on model systems suggested that HgCl2 interacts via the mercury atom with the carbon–carbon triple bond exclusively in ni-Zn. Powder X-ray diffraction enabled us to quantify the extent of the i-Zn-to-HgCl2@ni-Zn transition in 100–5000 ppm HgCl2 (aq) solutions, while X-ray fluorescence and inductively coupled plasma-mass spectrometry allowed us to demonstrate that HgCl2 is quantitatively sequestered from the aqueous phase. Irradiating at 365 nm, an intense fluorescence is observed at 470 nm for ni-Zn·S, which is partially quenched for i-Zn. This spectral benchmark was exploited to monitor in real time the i-Zn-to-HgCl2@ni-Zn conversion kinetics at different HgCl2 (aq) concentrations. A sizeable fluorescence increase was observed, within a 1 h time lapse, even at a concentration of 5 ppb. Overall, this comprehensive investigation unraveled an intriguing molecular mechanism, featuring the disaggregation of a water-stable MOF in the presence of HgCl2 and the self-assembly of a different crystalline phase around the pollutant, which is sequestered and simultaneously quantified by means of a luminescence change. Such a case study might open the way to new-conception strategies to achieve real-time sensing of mercury-containing pollutants in wastewaters and, eventually, pursue their straightforward and cost-effective purification.

Three metal−organic frameworks with the general formula Co(BPZX) (BPZX 2− = 3-X-4,4′-bipyrazolate, X = H, NH 2 , NO 2 ) constructed with ligands having different functional groups on the same skeleton have been employed as heterogeneous catalysts for aerobic liquid-phase oxidation of cumene with O 2 as oxidant. O 2 adsorption isotherms collected at p O2 = 1 atm and T = 195 and 273 K have cast light on the relative affinity of these catalysts for dioxygen. The highest gas uptake at 195 K is found for Co(BPZ) (3.2 mmol/g (10.1 wt % O 2 )), in line with its highest BET specific surface area (926 m 2 /g) in comparison with those of Co(BPZNH 2 ) (317 m 2 /g) and Co(BPZNO 2 ) (645 m 2 /g). The O 2 isosteric heat of adsorption (Q st ) trend follows the order Co(BPZ) > Co(BPZNH 2 ) > Co(BPZNO 2 ). Interestingly, the selectivity in the cumene oxidation products was found to be dependent on the tag present in the catalyst linker: while cumene hydroperoxide (CHP) is the main product obtained with Co(BPZ) (84% selectivity to CHP after 7 h, p O2 = 4 bar, and T = 363 K), further oxidation to 2-phenyl-2-propanol (PP) is observed in the presence of Co(BPZNH 2 ) as the catalyst (69% selectivity to PP under the same experimental conditions).

Aiming at extending the tagged zinc bipyrazolate metal–organic frameworks (MOFs) family, the ligand 3,3’‐diamino‐4,4’‐bipyrazole (3,3’‐H2L) has been synthesized in good yield. The reaction with zinc(II) acetate hydrate led to the related MOF Zn(3,3’‐L). The compound is isostructural with its mono(amino) analogue Zn(BPZNH2) and with Zn(3,5‐L), its isomeric parent built with 3,5‐diamino‐4,4’‐bipyrazole. The textural analysis has unveiled its micro‐/mesoporous nature, with a BET area of 463 m2 g−1. Its CO2 adsorption capacity (17.4 wt. % CO2 at pCO2 = 1 bar and T = 298 K) and isosteric heat of adsorption (Qst = 24.8 kJ mol−1) are comparable to that of Zn(3,5‐L). Both Zn(3,3’‐L) and Zn(3,5‐L) have been tested as heterogeneous catalysts in the reaction of CO2 with the epoxides epichlorohydrin and epibromohydrin to give the corresponding cyclic carbonates at T = 393 K and pCO2 = 5 bar under solvent‐ and co‐catalyst‐free conditions. In general, the conversions recorded are higher than those found for Zn(BPZNH2), proving that the insertion of an extra amino tag in the pores is beneficial for the epoxidation catalysis. The best catalytic match has been observed for the Zn(3,5‐L)/epichlorohydrin couple, with 64 % conversion and a TOF of 5.3 mmol(carbonate) (mmolZn)−1 h−1. To gain better insights on the MOF‐epoxide interaction, the crystal structure of the [epibromohydrin@Zn(3,3’‐L)] adduct has been solved, confirming the existence of Br⋅⋅⋅(H)−N non‐bonding interactions. To our knowledge, this study represents the first structural determination of a [epibromohydrin@MOF] adduct.

The UiO-67-type MIXMOF [Zr6O4(OH)4(PhPh)5(TzTz)], containing a blue-emitting bithiazole linker, is a potential multifunctional material for environmental remediation, being both a luminescent sensor and an adsorbent for diclofenac in aqueous solutions.