Severity: Warning
Message: file_get_contents(https://...@gmail.com&api_key=61f08fa0b96a73de8c900d749fcb997acc09&a=1): Failed to open stream: HTTP request failed! HTTP/1.1 429 Too Many Requests
Filename: helpers/my_audit_helper.php
Line Number: 197
Backtrace:
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 197
Function: file_get_contents
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 271
Function: simplexml_load_file_from_url
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 3165
Function: getPubMedXML
File: /var/www/html/application/controllers/Detail.php
Line: 597
Function: pubMedSearch_Global
File: /var/www/html/application/controllers/Detail.php
Line: 511
Function: pubMedGetRelatedKeyword
File: /var/www/html/index.php
Line: 317
Function: require_once
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Reticular materials constructed from chiral building blocks have garnered significant attention; however, the influence of their absolute configurations on framework structures and properties has yet to be elucidated. Herein, we report the stereoselective synthesis of covalent organic frameworks (COFs) through precise manipulation of the absolute configurations of chiral precursors. By selectively linking axially chiral binaphthalene-functionalized precursors with defined stereochemistry, we synthesized four ultrastable, highly crystalline isomeric three-dimensional COFs. Remarkably, two COFs are enantiomeric and adopt a chiral quartz () topology, while the other two exhibit an achiral diamondoid () topology─both outcomes governed solely by the specific pairing of absolute configurations. Moreover, these structural distinctions, particularly in framework chirality and pore environments, result in divergent chiral separation behaviors: the COFs effectively resolve racemates, whereas the COFs show no chiral separation ability. Our findings provide direct experimental evidence that absolute configuration can dictate not only framework chirality but also topology and function, offering new insights into the stereochemical control of reticular materials.
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Source |
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http://dx.doi.org/10.1021/jacs.5c09266 | DOI Listing |