Three UiO-66 samples were prepared by solvothermal synthesis using the defect engineering approach with benzoic acid as a modulator. They were characterized by different techniques and their acidic properties were assessed by FTIR spectroscopy of adsorbed CO and CD₃CN. All samples evacuated at room temperature contained bridging μ₃-OH groups that interacted with both probe molecules. Evacuation at 250 °C leads to the dehydroxylation and disappearance of the μ₃-OH groups. Modulator-free synthesis resulted in a material with open Zr sites. They were detected by low-temperature CO adsorption on a sample evacuated at 200 °C and by CD₃CN even on a sample evacuated at RT. However, these sites were lacking in the two samples obtained with a modulator. IR and Raman spectra revealed that in these cases, the Zr⁴⁺ defect sites were saturated by benzoates, which prevented their interaction with probe molecules. Finally, the dehydroxylation of all samples produced another kind of bare Zr sites that did not interact with CO but formed complexes with acetonitrile, probably due to structural rearrangement. The results showed that FTIR spectroscopy is a powerful tool for investigating the presence and availability of acid sites in UiO-66, which is crucial for its application in adsorption and catalysis.

The remediation of heavy metals (HMs) in soil is always an important topic, as environmental contamination by HMs is of serious concern. Numerous potential advantages, especially integrated with biochar produced from various biomass, might provide an ecologically beneficial tool for achieving the UN’s sustainable development objectives for greener soil remediation. The aim of this study was to address how the soil-science professions may best successfully utilize biochar for greener remediation of HMs-contaminated soils. In this context, the biochar preparation method from different agricultural feedstock, and its use as a soil amendment for remediation of HMs-contaminated soil, were discussed. Furthermore, biochar-based nanocomposites containing functional materials have lately attracted much interest because of the unique properties emerging from their nanoscale size compartment, and present good promise in terms of reactivity and stability. The utility and potency of biochar-based nanocomposites, on the other hand, are determined by their ability to adapt to particular site circumstances and soil qualities. This overview summarized the current advances in the application for the remediation of HMs-polluted soils. Future views on the usage and possibilities for deploying biochar-based nanocomposites in polluted soils were discussed.

We report here fast (15 min) microwave-assisted solvothermal synthesis of zeolitic imidazolate framework material (ZIF-7). We have optimized solvent composition to achieve high porosity and hydrogen capacity and narrow particle size distribution. It was shown that synthesis in N,N-diethylformamide (DEF) results in a layered ZIF-7 III phase, while N,N-dimethylformamide (DMF) as solvent leads to a pure ZIF-7 phase in microwave conditions. A mixture of toluene with DMF allows the production of pure ZIF-7 material only with the triethylamine additive. Obtained materials were comprehensively characterized. We have pointed out that both X-ray diffraction and infrared spectroscopy could be used for the identification of ZIF-7 or ZIF-7 III phases. Although samples obtained in DMF, and in a mixture of DMF, toluene, and triethylamine were assigned to the pure ZIF-7 phase, solvent composition significantly affected the size of particles in the material and nitrogen and hydrogen adsorption process.

Here, we report a new photosensitive metal–organic framework (MOF) that was constructed via the modification of UiO-66-NH₂ with diarylethene molecules (DAE, 4-(5-Methoxy-1,2-dimethyl-1H-indol-3-yl)-3-(2,5-dimethylthiophen-3-yl)-4-furan-2,5-dione). The material that was obtained was a highly crystalline porous compound. The photoresponse of the modified MOF was observed via UV–Vis and IR spectroscopy. Most of the DAE molecules inside of the UiO-66-pores had an open conformation after synthesis. However, the equilibrium was able to be shifted further toward an open conformation using visible light irradiation with a wavelength of 520 nm. Conversely, UV-light with a wavelength of 450 nm initiated the transformation of the photoresponsive moieties inside of the pores to a closed modification. We have shown that this transformation could be used to stimulate hydrogen adsorption–desorption processes. Specifically, visible light irradiation increased the H₂ capacity of modified MOF, while UV-light decreased it. A similar hybrid material with DAE moieties in the UiO-66 scaffold was applied for hydrogen storage for the first time. Additionally, the obtained results are promising for smart H₂ storage that is able to be managed via light stimuli.

Synchrotron-based X-ray absorption spectroscopy and scattering are known in situ probes of metal nanoparticles (NPs). A limited number of laboratory techniques allow post-synthesis diagnostics of the active metal surface area. This work demonstrates the high potential of infrared spectroscopy as an in situ laboratory probe for the growth of metal NPs on a substrate. We introduce a small fraction of CO molecules into the reaction mixture as a probe to monitor the reduction kinetics of the Pd²⁺ precursor on ceria in hydrogen.