A historical overview of the activation and porosity of MOFs including strategies to design and preserve permanent porosity in MOFs.

Novel dual physically cross-linked (DPC) hydrogels with great tensile strength, ultrahigh elongation, and promising repairability are designed by introducing cellulose nanocrystal (CNC) or hydrophobized CNC (CNC-C8) into polymers physically cross-linked by hydrophobic forces. C18 alkyl chain is grafted to N-[3-(dimethylamino)propyl]methacrylamide (DMAPMA) for hydrophobic monomer (DMAPMA-C18), and C8 to CNC surface for hydrophobic CNC (CNC-C8). CNC-C8 (or CNC) DPC hydrogels are synthesized, with monomers N,N-dimethylacrylamide (DMAc) and DMAPMA-C18 polymerized to form the first network physically cross-linked by hydrophobic interactions, on which the secondary cross-linking points are formed by hydrophobic interactions between CNC-C8 and DMAPMA-C18, electrostatic interactions between CNC-C8 (or CNC) and DMAPMA, as well as hydrogen bonding between CNC-C8 (or CNC) and DMAc. Compared with optimum CNC DPC hydrogels of the highest tensile strength (238 ± 8 kPa), the optimum CNC-C8 DPC hydrogel with 0.0675 w/v% DMAPMA-C18 and 0.4 w/v% CNC-C8 possesses stronger tensile strength of 331 ± 32 kPa and excellent elongation of 4268% ± 1446% as well, demonstrating the enhanced mechanical property of the hydrogel by introduced hydrophobic interactions. In addition, such DPC hydrogel can be facilely repaired with tetrahydrofuran (THF) on the cut surfaces while retaining good tensile stress and elongation behaviors.

Metal−organic frameworks (MOFs) have emerged as a highly tunable class of porous materials, and in particular, zirconium-based MOFs (Zr-MOFs) have demonstrated the potential to address challenges in a variety of practical applications due to their excellent chemical and thermal stabilities. However, Zr-MOFs are typically synthesized using flammable and toxic organic solvents. An effective, green, scalable route to obtain high-quality Zr-MOFs has yet to be developed as these procedures typically yield Zr-MOFs with relatively lower crystallinities and porosities than those obtained via the former route. Herein, we report the aqueous synthesis of MOF-808, a versatile Zr-MOF, that yields products with high crystallinities and porosities that are comparable to those of solvothermally synthesized MOF-808. We demonstrate that modifying the carboxylic acid-based modulator used in this hydrothermal procedure enables the straightforward tuning of the pore environment in MOF-808. This approach can be leveraged to tune both the water adsorption properties of MOF-808 and the solid-state catalytic performance of MOF-808 toward the hydrolysis of a nerve agent simulant. We anticipate that the insight gained here extends beyond MOF-808 and that it will lead to similar advancements for other Zr-MOFs.