Direct q 5 uv water purification system

O-salicylaldehyde; 3-amino pyridine; ethanol; nitrate salts of Al(III), Ba(II), Cd(II), Co(II), Cu(II), Fe(III), Mn(II), Ni(II), and Zn(II), and sulfate salt of Fe(II) were all purchased from Sigma-Aldrich (Steinheim, Germany) and dissolved in ultrapure water (Direct-Q 5 UV water purification system, Millipore, Burlington, MA, USA). The microwave reactions were carried out in a Biotage Initiator system (Biotage, Sweden), the temperature and time were preset as required, and the pressure was monitored and indicated. The identity of the products was determined by FTIR and NMR. FTIR analysis was performed on a Spectrum BX FTIR spectrometer (PerkinElmer, Waltham, MA, USA). The ¹H- and ¹³C-NMR spectra were recorded on a JNM-ECZR series 600 MHz spectrometer (JEOL, Tokyo, Japan) operating at 600 and 100 MHz, respectively, using DMSO-d6 as a solvent. The NMR is equipped with a Delta™ NMR data processing software. UV–VIS spectra were carried out using an Agilent 8453 spectrophotometer (Agilent, Santa Clara, CA, USA) in a 1.0 cm quartz cuvette. Fluorescence studies were performed on a PerkinElmer LS 45 Fluorescence spectrometer (PerkinElmer, Waltham, MA, USA) using a 1.0 cm quartz cuvette with a scan speed of 700 nm min⁻¹, and an excitation and emission slit of 10 nm each.

AgNO₃ (99.8%) and NaOH (99%) were purchased from Aladdin Industrial Co. Ltd. Cs₂CO₃ (99.9%), isopropyl alcohol (≥99.5%) and ethanol (HPLC, ≥99.8%) were purchased from Macklin Biochemical Co. Ltd. Sodium citrate anhydrous (99%) was purchased from J&K Scientific Ltd. L (+) − Ascorbic acid (≥99.7%) was purchased from Tianjin Kemiou Chemical Reagent Co. Ltd. All chemical reagents were utilized without further purification. Commercially available carbon-based GDLs (AvCarb GDS3250) were purchased from Xima Laya Photo-Electric Technology Co. Ltd., China. PiperION-A5-HCO₃ anion exchange resin, Fumion FAA anion exchange resin, PiperION-A15-HCO₃ and FAA-3-50 were purchased from SCI Materials Hub. CO₂, N₂, Ar and H₂ were all purchased from Air Liquide (≥99.999%). The ultrapure water (18.25 MΩ·cm) was supplied by a Millipore Direct-Q5 UV water purification system.

N-Methyl-d-glucaminemethylcalix[4]resorcinarenes were synthesized in two steps starting from calix[4]resorcinarenes with sulfonate and methyl groups on the lower rim obtained by a published method [20 (link),21 (link)]. N-Methyl-d-glucamine (99%, Acros Organics, Fair Lawn, NJ, USA) and 1-phenylazo-2-naphthol (Sudan I, Acros Organics) were used as received. Sample solutions were prepared in the deionized water (18.2 MΩ) obtained from a Direct-Q 5 UV water purification system (Millipore, Molsheim, France). The accurate pH was measured with a HI 2110 pH meter (Hanna Instruments, Woonsocket, RI, USA) calibrated using buffers according to the manufacturer’s instructions.