Chirality plays a very important role in medicine, biochemistry and other fields. Because the enantiomers of chiral drugs often show different pharmacology activity, metabolism, and toxicity, therefore, the recognition of chiral molecules is very important, and has become a hot spot and frontier of modern chemical research. In this paper, a new method for recognizing chiral molecular based on naphthalimide dye(NA)⊂cucurbit[5]uril(CB[7]) assembly is developed. NA as guest can be combined with the host CB[7] to form a 1:1 NA⊂CB[7] assembly. Furthermore, this assembly was used as a fluorescent probe to recognize D/L-phenylalanine and D/L-phenylalaninol by fluorescence titration. When D-phenylalanine or D-phenylalaninol was added to NA⊂CB[7] assembly, the fluorescent intensity of assembly was partially quenched, but when L-phenylalanine or L-phenylalaninol was added to NA⊂CB[7], the fluorescence intensity of the assembly almost unchanged. Herein, chiral recognition platform based on achiral NA⊂achiral CB[7] was constructed.
An in situ self-cleaning covalent organic framework featuring arylbiguanide arms (Aryl-BIG-COF) was first developed to remove emerging organic pollutants such as propranolol (PRO) from water. The main breakthroughs addressed the scarcity of functional active sites, the impracticality of ex situ regeneration, and the rapid recombination of electron hole pairs in the application of COFs. Owing to the directional capture ability and electronic structure regulation of the arylbiguanide arms, the adsorption capacity and photocatalytic degradation rate of the newly synthesized COF increased by nearly four and seven times, respectively. Its self-cleaning ability, driven by the photocatalytic regeneration of active sites, enabled in situ removal of PRO and sustained over 90 % removal efficiency after six cycles. Moreover, it demonstrated broad applicability for removing PRO and other emerging pollutants, such as bisphenol A (BPA), tetracycline (TC), and norfloxacin (NOR), across various water matrices with less residual toxicity. The coexisting organic matter and ions in natural water promoted the removal of PRO. The enhancement mechanism involved arylbiguanide arms narrowing the band gap and inducing local charge polarization, thereby increasing the separation efficiency of electron hole pairs. This work provides significant insights into the structural design and practical applications of COFs for purifying water.
Hydrogenations achieved on supported metal catalysts are normally structure sensitive, and comprehensive understandings on such sensitivity are pivotal for gaining insights into the active sites as well as the design of catalysts. Herein, a serials of differently sized Ru nanoparticles supported on carbon nanotube (CNT) were prepared and employed as catalysts for L-alanine hydrogenation to examine the structure sensitivity of amino acid hydrogenation. The reaction rates for L-alanine conversion and the formation of alaninol are demonstrated to be strongly dependent on the sizes of Ru nanoparticles, highlighting the structure sensitivity of the L-alanine hydrogenation. The activation energies extracted from kinetics studies are insensitive to the sizes of Ru nanoparticles on the Ru catalysts sized ≥1.3 nm with similar electronic properties, pointing to a predominant type of active site for L-alanine hydrogenation. By further combining model calculations with the shape of Ru nanoparticles determined by transmission electron microscopy, the Ru(101) sites are identified as the dominant active sites for L-alanine conversion and alaninol formation, which is further rationalized by density functional theory calculations. The kinetics insights into such structure sensitivity are believed to be important for the design and optimization of catalysts for the reaction.
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