Wet hydrogen peroxide catalytic oxidation (WHPCO) is one of the most important industrially applicable advanced oxidation processes (AOPs) for the decomposition of organic pollutants in water. It is demonstrated that manganese functionalized silicate nanoparticles with interparticle porosity act as a superior Fenton‐type nanocatalyst in WHPCO as they can decompose 80% of a test organic compound in 30 minutes at neutral pH and room temperature. By using X‐ray absorption spectroscopic techniques it is also shown that the superior activity of the nanocatalyst can be attributed uniquely to framework manganese, which decomposes H2O2 to reactive hydroxyls and, unlike manganese in Mn3O4 or Mn2O3 nanoparticles, does not promote the simultaneous decomposition of hydrogen peroxide. The presented material thus introduces a new family of Fenton nanocatalysts, which are environmentally friendly, cost‐effective, and possess superior efficiency for the decomposition of H2O2 to reactive hydroxyls (AOP), which in turn readily decompose organic pollutants dissolved in water.

Structural dynamics of Ca(BDC)(DMF)(H 2 O) with rhombic-shaped channels and 4 4 net topology upon heating and hydration were elucidated by using complementary methods of diffraction (XRD) and spectroscopy (FT-IR, MAS NMR, EXAFS, XANES). During heating the Ca(BDC)-(DMF)(H 2 O) framework underwent structural changes in two steps. The first change at 150 °C includes breaking of Ca−O bonds with H 2 O and DMF molecules. In this step, DMF is removed from the surface or near the surface of the crystals. The affected parts of the crystals are transformed to a new nonporous Ca-BDC(400) phase that prevents the diffusion of DMF from the cores of the crystals. Second transition at 400 °C led to the complete transformation to Ca-BDC(400). This phase is reversibly transformed to a pseudo-3-D framework Ca(BDC)(H 2 O) 3 upon exposure to humid environment. We proposed mechanisms of Ca-BDC(RT) → Ca-BDC(400) and Ca-BDC(400) → Ca(BDC)(H 2 O) 3 transformations, which include breaking of the bonds between Ca 2+ and carboxylate groups, rotating of BDC ligand, and recoordination of COO − groups to Ca 2+ centers. The crystal-to-crystal transformations are driven by the tendencies to change the bonding modes between COO − and Ca 2+ with the change of Ca 2+ coordination number. Thus the decrease in Ca 2+ coordination number, which is usually a consequence of activation, does not lead to the expansion or contraction of the pores, but it leads to pronounced structural rearrangement. Such behavior can explain the lack of porosity in Ca-MOF systems.

Four new magnesium 1,3,5-benzenetricarboxylate metal−organic framework materials (NICS-n; n = 3−6) were synthesized solvothermally in the presence of solvents with different EtOH/H 2 O ratios. We showed that the crystallization process of the Mg−1,3,5-benzentricarboxylate system strongly depends on the solvent composition, and that dimensionality of their structures can be tuned by changing the EtOH/water ratios in the reaction mixture. The presence of only water as a solvent yields the zero-dimensional molecular structure of Mg(structures were crystallized from EtOH/H 2 O mixtures with molar ratios of 0.3 and 0.4−0.7, respectively. The crystallization in pure ethanol yields Mg 3 (BTC) 2 material (NICS-6) with three-dimensional structure. Nuclear magnetic resonance investigations indicated that bulkier clusters of Mg species are formed in ethanol-rich solutions, even in the absence of the BTC ligand, and that the starting precursors formed with the reaction of Mg species and the BTC ligand at room temperature does not represent the final structures obtained by solvothermal reactions. NICS-4 and NICS-5 are formed from similar starting precursors but slightly different EtOH/H 2 O ratios causing the crystallization to go in two different directions. Systematic investigation of phase formation using different EtOH/H 2 O ratios, times, and temperatures of the synthesis along with the computational DFT studies confirmed that the 2D NICS-5 structure represents a thermodynamically more stable phase than 1D chainlike NICS-4. We showed that solvothermal reaction between Mg-precursors and the BTC ligand in EtOH/water mixture represents a complex and sensitive thermodynamic process.

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