A series of porous aromatic frameworks (PAFs) were synthesized via a Yamamoto-type Ullmann reaction containing quadricovalent Si (PAF-3) and Ge (PAF-4). These PAFs are thermally stable up to 465 °C for PAF-3 and 443 °C for PAF-4, corresponding to a 5% weight loss according to the TG pattern. As PAF-1, they exhibit high surface areas (up to 2932 m² g⁻¹) and excellent adsorption ability to hydrogen, methane and carbon dioxide. Low pressure gas uptake experiments on PAFs show PAF-3 has the highest heat of adsorption (Qst) of hydrogen (6.6 kJ mol⁻¹) and carbon dioxide (19.2 kJ mol⁻¹), while PAF-4 has the highest Qst for methane adsorption (23.2 kJ mol⁻¹) among PAFs. Gas molecule recognition at 273 K was performed and results show only greenhouse gases such as carbon dioxide and methane could be adsorbed onto PAFs.

We present two porous organic frameworks (POFs), PAF-1 and JUC-Z2, with ultrahigh iodine capture capacity. The iodine vapor uptake of PAF-1 and JUC-Z2 were 1.86 g g⁻¹ and 1.44 g g⁻¹ respectively at 298 K per 40 Pa, which is extremely high for such low pressure sorption conditions. In addition, PAF-1 and JUC-Z2 could adsorb iodine over water with the selectivity of 5.1 and 6.5 respectively. The isosteric enthalpy at zero surface coverage, calculated by a virial equation with the iodine vapor sorption isotherms at 298 K and 313 K of JUC-Z2, reached −51.1 kJ mol⁻¹, which was much higher than the coverage of PAF-1 (−14.9 kJ mol⁻¹). Raman measurement confirmed the polyiodide to be I₅ ⁻ in POFs. Furthermore, solvents with different polarities, such as n-hexane, chloroform, and methanol, were chosen to conduct iodine binding measurements on PAF-1 and JUC-Z2. The formation constant K_f for POFs in n-hexane, chloroform and methanol drastically decreased with the increase in polarity, thus illustrating the important role of solvents in iodine binding.

The creation of ultrahigh surface area materials are of great interest in academia and industry. In recent years, porous aromatic frameworks (PAF) were discovered and their porosity and properties were also explored. They are characterized by a rigid aromatic open-framework structure constructed by covalent bonds. The building block design, network formation method and relationship between functions and secondary building units were compiled in this highlight. In addition, advantages and challenges of predicted PAF derivatives were also discussed.