RESUMEN
A newly synthesized series of bimetallic CPM-37(Ni,Fe) metal-organic frameworks with different iron content (Ni/Fe ≈ 2, 1, 0.5, named CPM-37(Ni2Fe), CPM-37(NiFe) and CPM-37(NiFe2)) demonstrated high N2-based specific SBET surface areas of 2039, 1955, and 2378 m2 g-1 for CPM-37(Ni2Fe), CPM-37(NiFe), and CPM-37(NiFe2), having much higher values compared to the monometallic CPM-37(Ni) and CPM-37(Fe) with 87 and 368 m2 g-1 only. It is rationalized that the mixed-metal nature of the materials increases the structural robustness due to the better charge balance at the coordination bonded cluster, which opens interesting application-oriented possibilities for mixed-metal CPM-37 and other less-stable MOFs. In this work, the CPM-37-derived α,ß-Ni(OH)2, γ-NiO(OH), and, plausibly, γ-FeO(OH) phases obtained via decomposition in the alkaline medium demonstrated a potent electrocatalytic activity in the oxygen evolution reaction (OER). The ratio Ni : Fe ≈ 2 from CPM-37(Ni2Fe) showed the best OER activity with a small overpotential of 290 mV at 50 mA cm-2, low Tafel slope of 39 mV dec-1, and more stable OER performance compared to RuO2 after 20 h chronopotentiometry at 50 mA cm-2.
RESUMEN
In this study, four pozzolan-based geopolymers GP0, GP5, GP10, and GP20 were synthesized by alkaline activation and by substituting 0, 5, 10, and 20% of the precursor with sugarcane bagasse-derived biochar, respectively. The composites were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM/EDX), and Brunauer-Emmett-Teller (BET) surface area analyses, and applied to sequester methylene blue (MB) dye in an aqueous medium in batch mode. The alkaline activation of pozzolan-biochar blends resulted in the formation of poly (Ferro-sialate-siloxo)-biochar chains. The adsorption capacity increased with an increase in biochar content from 24.44 to 455.46 mg/g (18-fold) for GP0 and GP10, respectively. The sorption kinetics of MB onto the composites followed pseudo-second-order kinetics while the equilibrium data were best described by the Sips isotherm model. The adsorption process was thermodynamically spontaneous, endothermic (ΔH = 14.32-32.20 kJ/mol), and physical. The amount of adsorbent required for the removal of 99% of a fixed amount of MB in different volumes of effluent was predicted. Cost-analysis indicates that the composites are efficient and cheaper eco-adsorbents than commercial activated carbon and are suitable alternative candidates for the removal of dyes from water.