Covalent organic frameworks (COFs) are crystalline porous solids with well-defined two- or three-dimensional molecular structures. Although the structural regularity provides this new type of porous material with high potentials in catalysis, no example has been presented so far. Herein, we report the first application of a new COF material, COF-LZU1, for highly efficient catalysis. The easily prepared imine-linked COF-LZU1 possesses a two-dimensional eclipsed layered-sheet structure, making its incorporation with metal ions feasible. Via a simple post-treatment, a Pd(II)-containing COF, Pd/COF-LZU1, was accordingly synthesized, which showed excellent catalytic activity in catalyzing the Suzuki-Miyaura coupling reaction. The superior utility of Pd/COF-LZU1 in catalysis was elucidated by the broad scope of the reactants and the excellent yields (96-98%) of the reaction products, together with the high stability and easy recyclability of the catalyst. We expect that our approach will further boost research on designing and employing functional COF materials for catalysis.

The periodic layers and ordered nanochannels of covalent organic frameworks (COFs) make these materials viable open catalytic nanoreactors, but their low stability has precluded their practical implementation. Here we report the synthesis of a crystalline porous COF that is stable against water, strong acids and strong bases, and we demonstrate its utility as a material platform for structural design and functional development. We endowed a crystalline and porous imine-based COF with stability by incorporating methoxy groups into its pore walls to reinforce interlayer interactions. We subsequently converted the resulting achiral material into two distinct chiral organocatalysts, with the high crystallinity and porosity retained, by appending chiral centres and catalytically active sites on its channel walls. The COFs thus prepared combine catalytic activity, enantioselectivity and recyclability, which are attractive in heterogeneous organocatalysis, and were shown to promote asymmetric C-C bond formation in water under ambient conditions.

Purpose:To evaluate the value of diffusion-weighted imaging (DWI) in distinguishing between benign and malignant breast lesions. Materials and Methods:Fifty-two female subjects (mean age ϭ 58 years, age range ϭ 25-75 years) with histopathologically proven breast lesions underwent DWI of the breasts with a single-shot echo-planar imaging (EPI) sequence using large b values. The computed mean apparent diffusion coefficients (ADCs) of the breast lesions and cell density were then correlated. Results:The ADCs varied substantially between benign breast lesions ((1.57 Ϯ 0.23) ϫ 10 -3 mm 2 /second) and malignant breast lesions ((0.97 Ϯ 0.20) ϫ 10 -3 mm 2 /second). In addition, the mean ADCs of the breast lesions correlated well with tumor cellularity (P Ͻ 0.01, r ϭ -0.542). Conclusion:The ADC would be an effective parameter in distinguishing between malignant and benign breast lesions. Further, tumor cellularity has a significant influence on the ADCs obtained in both benign and malignant breast tumors.