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 (Qst) 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.

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Uranium capture from seawater could solve increasing energy demand and enable a much needed relaxing from fossil fuels. Low concentration (∼3 ppb), competing cations (especially vanadium) and pH-dependent speciation prohibit highly efficient uranium uptake. Despite intensive research, selective extraction of uranyl ions over vanadyl units remains a tremendous challenge. Here, we adopted a molecular coordination template strategy to design a uranyl-specific bis-salicylaldoxime entity and decorated it into a highly porous aromatic framework (PAF-1) by programmable assembly. The superstructure (MISS-PAF-1) gives a strong affinity that removes 99.97% of uranium in 120 min. Notably, it binds to the uranyl ion at least 100 times more selectively than 14 different cations tested, including the vanadyl ion, in simulated seawater at ambient pH. Real seawater samples collected from the Bohai Sea achieve 5.79 mg g –1 of uranium capacity over 56 days without PAF degradation, exceeding a 4-fold higher amount than commercial adsorbents.

opportunities, including facile separation and circulation of catalyst, easy purification of product, and continuous or multiple operations to address the tremendous requirements encountered in homogeneous catalysis. [7] One important characteristic is the confinement effect originating from the rigid cavity/channel of the solid platform. [8] In essence, as the pore size is adjusted to a reasonable range, the specific interaction between concave surface and substrate induces the subtle change of transition states and exerts great influence on the enantioselectivity in chiral synthesis. [9,10] It has been shown that some classical porous skeletons, such as inorganic solids (zeolites) and inorganic-organic hybrid solids (MOFs) have revealed a considerable substrate confinement effect. [11] However, the high proportion of inorganic constituents strongly disrupts the aromaticity of phenyl molecules due to the limitation of orbital spatial extension induced by the proximity of the pore walls. [12,13] The relatively low affinity results in an inadequate enantioselectivity for asymmetric catalysis, which cannot satisfy the strict standards for pure chiral substances put forth by the U.S. Food and Drug Administration. [12][13][14][15] As a novel type of crystalline solid, porous organic frameworks (POFs) have attracted a great deal of attention due to their promising applications in the fields of gas adsorption, [16] molecule separation, [17,18] optoelectronics, [19][20][21] etc. [22][23][24][25][26] In particular, POFs have shown great potential to serve as catalyst scaffolds due to their especially catalysis-friendly features, such as high permanent porosity, well-defined channels, and tuneable surfaces. [27][28][29][30][31][32][33] Their high proportions of conjugated components differ from the conventional porous matrices and will create specific affinities, such as hydrogen-π and π-π interactions for organic substances. Accordingly, the special confining reaction fields generated by POF channels may provide a new confinement effect for high-performance in asymmetric catalysis (Scheme 1).Herein, four 2D POF materials were synthesized with the same geometry and composition but with different pore diameters within the range of 1.2-2.9 nm by tuning the length of linkers (Figure 1). Through a facile post-modification, a chiralThe asymmetric hydrogenation of biomass-derived molecules for the preparation of single enantiomer compounds is an effective method to reduce the rapid consumption of fossil resources. Porous organic frameworks (POFs) with pure organic surfaces may provide unusual confinement effects for organic substrates in chiral catalysis. Here, a series of POF catalysts are designed with chiral active centers decorated into sharply defined onedimensional channels with diameters in the range of 1.2-2.9 nm. Due to the synergistic effect originating from the conjugated inner wall, the POF material (aperture size 2.4 nm) concentrates over 90% of aromatic species into the porous architecture, and its affinity is one...

Fully reduced polyoxometalates are predicted to give rise to broad and strong absorption spectrum, suitable energy levels, unparalleled electronic and optical properties, however, they are not available to date. Here,...