One-pot Construction of Metal Nanoparticles Loaded COF Catalysts for Aqueous Hydrogenation Reactions.

The catalysis performance of metal nanoparticles (NPs) will be significantly deteriorated because of their spontaneous agglomeration during practical applications. Covalent-organic frameworks (COFs) materials with functional groups and well-defined channels benefit for the dispersion and anchor of metal ions and the confined growth of metal NPs, working as an ideal platform to compose catalytic systems. In this article, we report a one-pot strategy for the preparation of metal NPs loaded COFs without the need of post-modification. During the polymerization process, the pre-added metal ions were stabilized by the rapidly formed COF oligomers and hardly disturb the construction of COFs. After reduction, metal NPs are uniformly anchored on the COF matrix. Eventually, a wide spectrum of metal NPs, including Au, Pd, Pt, AuPd, CuPd, CuPt and CuPdPt, loaded COFs are successfully prepared. The versatility and metal ions anchoring mechanism are verified with four different COF matrixes. Taking AuPd NPs as example, the resultant AuPd NPs loaded COF materials can selectively decompose ammonium formate and produce hydrogen in-situ, exhibiting over 99 % conversion of hydrodechlorination for chlorobenzenes and nitro-reduction reaction for nitroaromatic compounds under ambient temperature in aqueous solution.

A Thermally Promoted Homogenous-Floating-Concentrating Strategy Synthesizing Highly Crystalline Triazine/hydroxyl-Rich COFs for 4-Nitrophenol Adsorption.

In this work, a "thermally promoted homogenous-floating-concentrating" strategy is reported for the rapid synthesis of highly crystalline triazine/hydroxyl-rich COFs under mild conditions, using for the effectively adsorbing 4-nitrophenol (4-NP) in aqueous solutions. This strategy originates from an optimized "homogenous-floating-concentrating" method as reported in the previous work. Both gradually improving concentration and heat treatment promote the condensation reaction between amino and aldehyde groups, resulting in high crystallinity and shorter reaction time. The obtained COFs demonstrate better crystallinity and higher surface area in comparison with the counterparts prepared by solvothermal strategy. A maximum surface area of 2391 m2 g-1 is achieved. The COFs exhibit excellent 4-NP adsorption capacity (Qmax = 1402.0 mg g-1 ), which is attributed to abundant triazine/hydroxyl-groups on the COF skeleton and their strong H-bonding interaction with 4-NP.

A selective sensing platform for the simultaneous detection of ascorbic acid, dopamine, and uric acid based on AuNPs/carboxylated COFs/Poly(fuchsin basic) film.

In this study, an electrochemical sensing strategy was developed based on the synergies of gold nanoparticles (AuNPs) doped carboxylated covalent organic frameworks (ACOFs) and poly(fuchsin basic) film for the simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). This strategy not only took advantage of the adopted materials but also made use of the H-bonding and electrostatic interaction between the three compounds and materials. For this sensing, a poly-BFu film was formed on the surface of bare glass carbon electrode (GCE) under a constant potential. AuNPs was highly dispersed and immobilized on the constructed ACOF-TaTp to obtain AuNPs@ACOF. The constructed sensor AuNPs@ACOF/p-BFu/GCE combined the merits of high surface area, hydrophilicity, conductivity, and selective affinity, consequently exhibiting high sensitivity and selectivity toward the simultaneous detection of AA, DA, and UA with wide linear response ranges of 25-1500 µM, 0.75-40 µM, and 1-200 µM, respectively. The corresponding detection limits were 12.0 µM, 0.15 µM, and 0.22 µM. The simultaneous determination of UA in real human urine sample further confirmed the practicability of the designed electrode.

Homogeneous Polymerization of Self-standing Covalent Organic Framework Films with High Performance in Molecular Separation.

Covalent organic frameworks (COFs) are typically isolated as microcrystalline powders. It remains fundamentally challenging to fabricate COFs into high-quality self-standing films to take full advantage of their ordered pore channels for molecular separation. Here, we report a new strategy for fabricating self-standing imine-linked COF films via homogeneous polymerization where films emerge from clear solutions without forming amorphous precipitates. The abundant basic nitrogen atoms of the monomers acted as a reaction controller to realize the homogeneous polymerization and also promoted the tight self-aggregation of COF crystallites to form compact films via H-bonding. The chemically supported self-standing COF films on nylon membranes were also developed via an in situ growth method. The resulting films showed an unprecedentedly ultrafast permeance of 2822 L m-2 h-1 MPa-1 with a high rejection rate (99.8%) in the filtration of a congo red (CR) solution, demonstrating the advantage of this new strategy in fabricating high-quality self-standing COF films.