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The covalent organic frameworks (COFs) with olefin linkages are attractive materials for nonlinear optics due to their small energy band gap and large π‐electron separation domain. In this paper, a post‐synthetic modification (PSM) by applying a heck coupling reaction on olefin‐linked COFs was applied for the first time to obtain five functionalized triazine‐based covalent organic framework materials. The synthesized materials were tested for their relevant photophysical and electrochemical properties, and their third‐order nonlinear optical properties were tested using the Z‐scan technique. The experimental results indicate that the post‐modified COF (W4‐2) exhibits third‐order nonlinear polarizability χ3 that is 1.51 times higher than the unmodified COF (W4). [ABSTRACT FROM AUTHOR]

The structural diversity of three‐dimensional (3D) covalent organic frameworks (COFs) are limited as there are only a few choices of building units with multiple symmetrically distributed connection sites. To date, 4 and 6‐connected stereoscopic nodes with Td, D3h, D3d and C3 symmetries have been mostly reported, delivering limited 3D topologies. We propose an efficient approach to expand the 3D COF repertoire by introducing a high‐valency quadrangular prism (D4h) stereoscopic node with a connectivity of eight, based on which two isoreticular 3D imine‐linked COFs can be created. Low‐dose electron microscopy allows the direct visualization of their 2‐fold interpenetrated bcu networks. These 3D COFs are endowed with unique pore architectures and strong molecular binding sites, and exhibit excellent performance in separating C2H2/CO2 and C2H2/CH4 gas pairs. The introduction of high‐valency stereoscopic nodes would lead to an outburst of new topologies for 3D COFs. [ABSTRACT FROM AUTHOR]

Summary: Graph is one of the most important data structures to model social networks and becomes popular to find interesting relationships between individuals. Since graphs may contain sensitive information, data curators usually need to anonymize the graph before publication to prevent individual re‐identification, which thus leads to plenty of anonymized graphs for data sharing and exploration. However, the new structures and properties of anonymized graphs make the traditional graph indexing method inefficient or even invalid for query processing. To address the subgraph query problem over anonymized graph database, in this paper, we first introduce basic concepts about anonymized graphs and subgraph queries, then propose an index structure named Closure+‐tree to process the subgraph query efficiently. In particular, graphs were organized hierarchically that each node is an union of its child nodes under some specified mapping functions. During the processing of subgraph queries, the whole graph descendants will be pruned if their union does not contain the query graph. To evaluate the performance of our proposed Closure+‐tree, extensive experiments are performed on both real and synthetic graph data sets. The experimental results revealed that our index structure can prune up to 80% unqualified graphs with variable size of queries. Furthermore, the size of our index structure is only around a quarter of the entire anonymized graph data set, which indicates good scalability over large data sets. [ABSTRACT FROM AUTHOR]