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The electronic conductivity (EC) of metal–organic frameworks (MOFs) is sensitive to strongly oxidizing guest molecules. Water is a relatively mild species, however, the effect of H2O on the EC of MOFs is rarely reported. We explored the effect of H2O on the EC in the MOFs (NH2)2‐MIL‐125 and its derivatives with experimental and theoretical investigations. Unexpectedly, a large EC increase of 107 on H2SO4@(NH2)2‐MIL‐125 by H2O was observed. Brønsted acid–base pairs formed with the −NH2 groups, and H2SO4 played an important role in promoting the charge transfer from H2O to the MOF. Based on H2SO4@(NH2)2‐MIL‐125, a high‐performance chemiresistive humidity sensor was developed with the highest sensitivity, broadest detection range, and lowest limit of detection amongst all reported sensing materials to date. This work not only demonstrated that H2O can remarkably influence the EC of MOFs, but it also revealed that post‐modification of the structure of MOFs could enhance the influence of the guest molecule on their EC to design high‐performance sensing materials. [ABSTRACT FROM AUTHOR]

Porous organic polymers (POPs) with high porosity and tunable functionalities have been widely studied for use in gas separation, catalysis, energy conversion and energy storage. However, the high cost of organic monomers, and the use of toxic solvents and high temperatures during synthesis pose obstacles for large‐scale production. Herein, we report the synthesis of imine and aminal‐linked POPs using inexpensive diamine and dialdehyde monomers in green solvents. Theoretical calculations and control experiments show that using meta‐diamines is crucial for forming aminal linkages and branching porous networks from [2+2] polycondensation reactions. The method demonstrates good generality in that 6 POPs were successfully synthesized from different monomers. Additionally, we scaled up the synthesis in ethanol at room temperature, resulting in the production of POPs in sub‐kilogram quantities at a relatively low cost. Proof‐of‐concept studies demonstrate that the POPs can be used as high‐performance sorbents for CO2 separation and as porous substrates for efficient heterogeneous catalysis. This method provides an environmentally friendly and cost‐effective approach for large‐scale synthesis of various POPs. [ABSTRACT FROM AUTHOR]

Designing porous materials for C2H2 purification and safe storage is essential research for industrial utilization. We emphatically regulate the metal‐alkyne interaction of PdII and PtII on C2H2 sorption and C2H2/CO2 separation in two isostructural NbO metal–organic frameworks (MOFs), Pd/Cu‐PDA and Pt/Cu‐PDA. The experimental investigations and systematic theoretical calculations reveal that PdII in Pd/Cu‐PDA undergoes spontaneous chemical reaction with C2H2, leading to irreversible structural collapse and loss of C2H2/CO2 sorption and separation. Contrarily, PtII in Pt/Cu‐PDA shows strong di‐σ bond interaction with C2H2 to form specific π‐complexation, contributing to high C2H2 capture (28.7 cm3 g−1 at 0.01 bar and 153 cm3 g−1 at 1 bar). The reusable Pt/Cu‐PDA efficiently separates C2H2 from C2H2/CO2 mixtures with satisfying selectivity and C2H2 capacity (37 min g−1). This research provides valuable insight into designing high‐performance MOFs for gas sorption and separation. [ABSTRACT FROM AUTHOR]

The hydrolysis of earth‐abundant AlIII has implications in mineral mimicry, geochemistry and environmental chemistry. Third‐order nonlinear optical (NLO) materials are important in modern chemistry due to their extensive optical applications. The assembly of AlIII ions with π‐conjugated carboxylate ligands is carried out and the hydrolysis and NLO properties of the resultant material are studied. A series of Al32‐oxo clusters with hydrotalcite‐like cores and π‐conjugated shells are isolated. X‐ray diffraction revealed boundary hydrolysis occurs at the equatorially unsaturated coordination sites of AlIII ions. Charge distribution analysis and DFT calculations support the proposed boundary substitution. The Al32‐oxo clusters possess a significant reverse saturable absorption (RSA) response with a minimal normalized transmittance up to 29 %, indicating they are suitable candidates for optical limiting (OL) materials. This work elucidates the hydrolysis of AlIII and provides insight into layered materials that also have strong boundary activity at the edges or corners. [ABSTRACT FROM AUTHOR]

Many metal–organic cages (MOCs) and a few hydrogen‐bonded organic cages (HOCs) have been investigated, but little is reported about cooperative self‐assembly of MOCs and HOCs. Herein, we describe an unprecedented MOC&HOC co‐crystal composed of tetrahedral Ti4L6 (L=embonate) cages and in‐situ‐generated [(NH3)4(TIPA)4] (TIPA=tris(4‐(1H‐1,2,4‐triazol‐1‐yl)phenyl)amine) cages. Chiral transfer is observed from the enantiopure Ti4L6 cage to enantiopure [(NH3)4(TIPA)4] cage. Two homochiral supramolecular frameworks with opposite handedness (PTC‐235(Δ) and PTC‐235(Λ)) are formed. Such MOC&HOC co‐crystal features high stability in water and other solvents, affording single‐crystal‐to‐single‐crystal transformation to trap CH3CN molecules and identify disordered NH4+ cations. A tablet pressing method is developed to test the third‐order nonlinear optical property of KBr‐based PTC‐235 thin film. Such a thin film exhibits an excellent optical limiting effect. [ABSTRACT FROM AUTHOR]