3flex apparatus

The gel microspheres were dried under supercritical CO₂ conditions (74 bar, 31.5 °C) using a PolaronE3100 Critical Point Dryer (Quorum Technologies). Thermo-gravimetric analysis (TGA) was conducted under air using TA Instrument Q500 apparatus, with a 10 °C min⁻¹ ramp between 25 and 1000 °C. Fourier transform infrared (FT-IR) spectra of samples in KBr pellets were measured on a Bruker Vector 22 spectrometer. X-ray diffraction patterns of the uncalcined and calcined xerogel and aerogel spheres were recorded on a Bruker AXS D-8 diffractometer using Cu-Kα radiation in Bragg–Brentano geometry (θ–2θ). Scanning electron microscopy (SEM) micrographs were obtained using an FEI Quanta 200 microscope after carbon metallization. TEM micrographs were obtained on a Tecnai G2 microscope at 120 kV. Nitrogen adsorption/desorption isotherms were recorded using Micromeritics 3Flex apparatus at 77 K after outgassing the sample at 150 °C overnight. The surface areas were determined from the nitrogen adsorption/desorption isotherms, using the BET (Brunauer–Emmett–Teller) method. The pore size distributions were determined according to the BJH (Barrett–Joyner–Halenda) method. RTPL analysis was performed using a Horiba Yvon Jobin spectrophotometer.

The measurement of H₂O adsorption isotherms was performed using the manometric equipment, a 3 Flex apparatus from Micromeritics. Water adsorption isotherm data were collected at 298 K from 0 to 2.1 kPa. Prior to each measurement, the material samples were degassed under a dynamic vacuum at 393 K for 12 h, and the sample holder dead volume was measured from helium expansion.
Material aging and stability to moisture were assessed during storage under atmospheric humid conditions by leaving the adsorbent samples inside a room at a controlled temperature of 25 ± 5 °C and at a relative humidity (RH) of 40 ± 5% for a duration of 3 months. The properties of the stored samples were then re-characterized via measurements of the N₂ adsorption isotherms at 77 K and CO₂ adsorption isotherms up to 1 bar at 298 K.

All TiO₂ nanopowders were purchased from US Research Nanomaterials (≥99.5% purity). The samples included both pristine allotropic forms of TiO₂ (rutile and anatase) and their defined mixtures. According to the manufacturer, the particle size varied from 5 to 800 nm. Aeroxide P25 was purchased from Evonik (≥99.5% purity). In the labeling of the samples, the letters A, R, A+R, and AM designate anatase, rutile, anatase+rutile mixed phases, and “amorphous” TiO₂ as well as the number indicating the nominal particle size, as given by the producer.
The structural and textural properties of the nanoparticles were determined by a combination of several techniques. Surface morphology was followed with scanning electron microscopy (SEM, JEOL JSM 5500LV) combined with high-resolution transmission electron microscopy (HR-TEM, JEOL JEM-2100Plus). Crystallinity (structure and phase composition) of the titania dioxide samples was evaluated by powder X-ray diffraction (pXRD) using PANalytical X′Pert PRO diffractometer equipped with Co anode in the Bragg-Brentano geometry and multichannel X′Celerator detector. The surface area of powders was determined from nitrogen sorption isotherms at the boiling point of liquid nitrogen using a Micromeritics 3Flex apparatus. Prior to the measurements, the samples were degassed at 250 °C overnight.

Sorption isotherms of Kr were measured at the boiling point of liquid nitrogen (ca. 77 K) using a 3Flex apparatus (Micromeritics, Norcross, GA, USA). The surface area was calculated by the BET equation.