Porous aromatic frameworks (PAFs), which are well-known for their large surface areas, associated porosity, diverse structures, and superb stability, have recently attracted broad interest. Taking advantage of widely available building blocks and various coupling strategies, customized porous architectures can be prepared exclusively through covalent bonding to satisfy necessary requirements. In addition, PAFs are composed of phenyl-ring-derived fragments that are easily modified with desired functional groups with the help of established synthetic chemistry techniques. On the basis of material design and preparative chemistry, this review mainly focuses on recent advances in the structural and chemical characteristics of PAFs for potential utilizations, including molecule storage, gas separation, catalysis, and ion extraction. Additionally, a concise outlook on the rational construction of functional PAFs is discussed in terms of developing next-generation porous materials for broader applications.

Ammonia (NH₃) is a commonly used industrial gas, but its corrosiveness and toxicity are hazardous to human health. Although many adsorbents have been investigated for NH₃ sorption, limited ammonia uptake remains an urgent issue yet to be solved. In this article, a series of multivariate covalent organic frameworks (COFs) are explored which are densely functionalized with various active groups, such as —N—H, —C═O, and carboxyl group. Then, a metal ion (Ca²⁺, Mn²⁺, and Sr²⁺) is integrated into the carboxylated structure achieving the first case of an open metal site in COF architecture. X-ray photoelectron spectroscopy reveals conclusive evidence for the multiple binding interactions with ammonia in the modified COF materials. Infrared spectroscopy indicates a general trend of binding capability from weak to strong along with —N—H, —C═O, carboxyl group, and metal ion. Through the synergistic multivariate and open metal site, the COF materials show excellent adsorption capacities (14.3 and 19.8 mmol g^–1 at 298 and 283 K, respectively) and isosteric heat (Q_st) of 91.2 kJ mol^–1 for ammonia molecules. This novel approach enables the development of tailor-made porous materials with tunable pore-engineered surface for ammonia uptake.

Tetrakis(4-bromophenyl)methane (TBPM) as a tetrahedral unit and a diboronic acid as a linker were selected to couple the phenyl rings into a porous aromatic framework, PAF-11. PAF-11 was polymerized via a Suzuki coupling reaction. A TG analysis showed that PAF-11 is thermally stable up to 400 °C in air. PAF-11 also has a high chemical stability and cannot be dissolved or decomposed in common solvents or concentrated hydrochloric acid. A N₂ sorption measurement on activated PAF-11 revealed a surface area of 952 m² g⁻¹ in the Langmuir model. PAF-11 also shows a considerable adsorption capacity for H₂. Interestingly, PAF-11 is a highly hydrophobic material but with a high methanol uptake (654 mg g⁻¹ at saturated vapour pressure and room temperature). PAF-11 also exhibits high adsorption abilities for small aromatic molecules such as benzene and toluene (874 and 780 mg g⁻¹, respectively, at saturated vapour pressure and room temperature) due to its aromatic framework. This ability of PAF-11 could be very useful to eliminate harmful small aromatic molecules produced by industry.