A metakaolin/slag-based porous geopolymer (non-sintered ceramic) was prepared using a simple direct molding method, and the copper metal–organic frameworks (Cu-MOFs) were grown in situ via a solvothermal process. The Cu-MOFs/geopolymer composites achieve a ~98% degradation rate for tetracycline hydrochloride (TCH) within 10 min via peroxymonosulfate (PMS) activation at pH = 11. Radicals (·OH, SO₄^•−, and O₂^•−) and non-radicals (¹O₂) were identified as the dominant reactive oxygen species (ROS) participating in the catalytic process. Cu-MOFs/geopolymer acts as an electron transfer medium between TCH molecules and PMS molecules, enabling the efficient degradation of TCH. Furthermore, the catalytic system exhibited excellent cyclic stability, pH adaptability, and resistance to ionic interference, demonstrating superior performance in a flow-through fixed-bed reactor simulating real wastewater. The practical application of this system in wastewater treatment can be beneficial for reducing energy consumption, enhancing environmental sustainability, and lowering catalyst costs.

Porous geopolymer precursors were firstly prepared by the direct foaming method using bauxite, fly ash (FA), and metakaolin (MK) as raw materials, and porous mullite ceramics were prepared after ammonium ion exchange and then high-temperature sintering. The effects of chemical foaming agent concentration, ion-exchange time, and sintering temperature on porous geopolymer-derived mullite ceramics were studied, and the optimal preparation parameters were found. Studies have shown that the concentration of blowing agent had great influence on open porosity (q) and porosity and cell size distributions of geopolymer samples, which in turn affected their compressive strength (σ). Duration of the ion exchange had no obvious effect on the sintered samples, and the amount of mullite phase increased with the increase in the sintering temperature. Mullite foams, possessing an open-celled porous structure, closely resembling that of the starting porous geopolymers produced by directly foaming, were obtained by firing at high temperatures. Stable mullite (3Al₂O₃·2SiO₂) ceramic foams with total porosity (ε) of 83.52 vol%, high open porosity of 83.23 vol%, and compressive strength of 1.72 MPa were produced after sintering at 1400 ℃ for 2 h in air without adding any sintering additives using commercial MK, bauxite, and FA as raw materials.