Porous aromatic frameworks (PAFs) represent an important category of porous solids. PAFs possess rigid frameworks and exceptionally high surface areas, and, uniquely, they are constructed from carbon−carbon−bond−linked aromatic-based building units. Various functionalities can either originate from the intrinsic chemistry of their building units or are achieved by postmodification of the aromatic motifs using established reactions. Specially, the strong carbon−carbon bonding renders PAFs stable under harsh chemical treatments. Therefore, PAFs exhibit specificity in their chemistry and functionalities compared with conventional porous materials such as zeolites and metal organic frameworks. The unique features of PAFs render them being tolerant of severe environments and readily functionalized by harsh chemical treatments. The research field of PAFs has experienced rapid expansion over the past decade, and it is necessary to provide a comprehensive guide to the essential development of the field at this stage. Regarding research into PAFs, the synthesis, functionalization, and applications are the three most important topics. In this thematic review, the three topics are comprehensively explained and aptly exemplified to shed light on developments in the field. Current questions and a perspective outlook will be summarized. CONTENTS 3. General Strategies and Examples For PAF Functionalization 8951 3.1. Direct Synthesis 8951 3.2. Postsynthetic Modification 8952 3.3. Post Modification of PAFs with Preanchored Sites 8953 3.4. PAFs with Charged Frameworks 8953 3.5. Wettability and Polarity of PAF Frameworks 8953 4. State-of-the-Art of PAF Applications 8954 4.1. Gas Adsorption 8954 4.1.1. Hydrogen Storage 8954 4.1.2. Methane Adsorption 8958 4.1.3. CO 2 Capture 8960 4.1.4. Adsorptive Separation of Hydrocarbon Mixtures 8965 4.1.5. Capture of Ammonia 8966 4.2. Membrane Separation 8966 4.3. Adsorption of Hazardous Organic Compounds 8968 4.3.1. Capture of Hazardous Organic Chemicals 8968 4.3.2. Enrichment of Trace Organic Compounds for Analysis 8969

The targeted synthesis of a series of novel charged porous aromatic frameworks (PAFs) is reported. The compounds PAF-23, PAF-24, and PAF-25 are built up by a tetrahedral building unit, lithium tetrakis(4-iodophenyl)borate (LTIPB), and different alkyne monomers as linkers by a Sonogashira-Hagihara coupling reaction. They possess excellent adsorption properties to organic molecules owing to their "breathing" dynamic frameworks. As these PAF materials assemble three effective sorption sites, namely the ion bond, phenyl ring, and triple bond together, they exhibit high affinity and capacity for iodine molecules. To the best of our knowledge, these PAF materials give the highest adsorption values among all porous materials (zeolites, metal-organic frameworks, and porous organic frameworks) reported to date.

The separation of acetylene from ethylene is a crucial process in the petrochemical industry, as even small acetylene impurities can lead to premature termination of ethylene polymerization. Herein, we present the synthesis of a robust, crystalline naphthalene diimide porous aromatic framework via imidization of linear naphthalene-1,4,5,8-tetracarboxylic dianhydride and triangular tris­(4-aminophenyl)­amine. The resulting material, PAF-110, exhibits impressive thermal and long-term structural stability, as indicated by thermogravimetric analysis and powder X-ray diffraction characterization. Gas adsorption characterization reveals that PAF-110 has a capacity for acetylene that is more than twice its ethylene capacity at 273 K and 1 bar, and it exhibits a moderate acetylene selectivity of 3.9 at 298 K and 1 bar. Complementary computational investigation of each guest binding in PAF-110 suggests that this affinity and selectivity for acetylene arises from its stronger electrostatic interaction with the carbonyl oxygen atoms of the framework. To the best of our knowledge, PAF-110 is the first crystalline porous organic material to exhibit selective adsorption of acetylene over ethylene, and its properties may provide insight into the further optimized design of porous organic materials for this key gas separation.

Enhancing the activity and stability of enzymes and improving their reusability are critical challenges in the field of enzyme immobilization. Here we report a facile and efficient biomimetic mineralization to embed thermophilic lipase QLM in zeolite imidazolate framework-8 (ZIF-8). Systematic characterization indicated that the entrapment of lipase molecules was successfully achieved during the crystal growth of ZIF-8 with an enzyme loading of ∼72.2 ± 1.88 mg/g lipase@ZIF-8, and the enzymes could facilitate the construction of framework building blocks. Then the composite lipase@ZIF-8 was observed to possess favorable catalytic activity and stability in the ester hydrolysis, using the hydrolysis of p-nitrophenyl caprylate as a model. Finally, the composite was successfully applied in the kinetic resolution of (R,S)-2-octanol, with favorable catalytic activity and enantioselectivity during 10 cycle reactions. Thus, the biomimetic mineralization process can be potentially used as an effective technique for realizing the entrapment of biomacromolecules and constructing efficient catalysts for industrial biocatalysis.

Structure transformation of germanosilicate zeolites ITH, ITR, and IWR containing hydrolytically unstable interlayer Ge–O bonds was investigated and is related to the conditions of acidic treatment (i.e., concentration of hydrochloric acid, temperature, duration). The disassembly of ITH (Si/Ge = 2.5), ITR (Si/Ge = 2.4), and IWR (Si/Ge = 6.9) zeolites under appropriate acidic treatment was demonstrated. Low-concentration acid solutions (e.g., 0.01 M HCl) and low temperatures favor the hydrolysis of the zeolites under study. The chemical composition of the parent zeolites strongly influences the efficiency of hydrolysis. For zeolites having sufficient fraction (ca. 50%) of Ge in D4R units (Si/Ge ≤ 6 for ITH and IWR, Si/Ge ≤ 3.7 for ITR), transformation into layered materials (two-dimensional zeolites) was successful while the lowering of Ge concentration resulted in only a partial separation of the ITH and ITR crystalline layers. The acidic treatment of medium-pore ITR and ITH zeolites with HCl at ambient temperature for 24 h is optimal for selective cleavage of almost all interlayer Ge–O bonds, while transformation of large-pore IWR zeolite into layered material was observed even after only 5 min of the treatment. These results evidence the general applicability of the ADOR mechanism for the synthesis of new zeolites.