Efficient Ammonia Sequestration by Al-Based MOF Composites: Synergistic Regulation of Supports and Loading Strategies and Investigation of the Adsorption Mechanism

This study employed 3,5-pyrazoledicarboxylic acid (PZDC) as a ligand to synthesize aluminum-based metal-organic frameworks (Al-PZDC) via an in-situ hydrothermal method. Al-PZDC composites were constructed using two loading methods—preloading and postloading—with 13X molecular sieves, activated carbon, and γ-Al 2 O 3 as carriers, respectively. The physicochemical properties of the materials were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), BET specific surface area analysis , scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The NH 3 adsorption mechanism was investigated by combining adsorption kinetic models, pre- and post-adsorption spectral analysis, and in situ differential Raman infrared spectroscopy (Insitu DRIFTS). The results indicate that Al-PZDC was successfully loaded onto each carrier; Composites prepared by the pre-loading method exhibited superior adsorption performance compared to those from the post-loading method. The composite (13X molecular sieve @Al-PZDC-0.4) prepared using 13X molecular sieve as the carrier and the pre-loading method demonstrated the most outstanding NH 3 adsorption performance, achieving a saturation adsorption capacity of 100.57 mg·g -1 at 25°C and 1% NH 3 concentration. Kinetics analysis indicates that NH 3 adsorption is primarily chemical adsorption supplemented by physical adsorption. The adsorption mechanism involves physical adsorption, pore filling, hydrogen bonding interactions, and the synergistic effects of Lewis acid (L-acid) and Brønsted acid (B-acid) sites.