Contrasting-functionality-decked robust MOF for moisture-tolerant and variable-temperature CO2 adsorption with in-built urea group mediated mild condition cycloaddition

Manpreet Singh, Partha Pratim Mondal, Sonal Rajput, Subhadip Neogi

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

The dire need to reduce the atmospheric carbon dioxide (CO2) concentration has attracted worldwide attention to the capture of this greenhouse gas and its conversion into useful chemicals. Nevertheless, it is still difficult to achieve variable-temperature and humid-condition adsorption with mild condition fixation of CO2 in metal-organic frameworks (MOFs) due to difficulties in positioning assorted task-specific sites. We introduced open metal site (OMS), hydrogen-bond operative functionality, and free amine moiety inside the pore wall of a mixed-ligand robust Cd(ii) framework. Two-fold interpenetration generated high-density acid-base functionalization promotes appreciable CO2 adsorption in the guest-free structure at elevated temperature with considerable MOF-CO2 interaction. The aqua-robust MOF exhibits minimum loss in CO2 uptake during multiple capture-release cycles under variable temperature and retains the adsorption capacities even upon exposure to 75% RH. The atomistic-level snapshots of temperature-induced inclusion of gas molecules inside this microporous vessel are rationalized from simulation studies, and portray diverse CO2-philic sites. Particularly, the four-fold increased CO2 adsorption compared to that of an un-functionalized MOF validates the prime role of pore surface engineering. Moreover, the CO2 selectivity shows a drastic improvement upon gradually increasing the temperature, attaining a CO2/N2 value of 380 at 313 K. The framework further demonstrates solvent-free CO2 conversion to cyclic carbonates in high yield with broad substrate scope and satisfactory reusability under less harsh conditions and in a rather short time. In addition to typical OMS/co-catalyst synergism, the mutual participation of antagonistic active sites in substrate interaction and activation is validated by juxtaposing the performance of a urea-free isoskeletal framework and by the relative fluorescence modification in the presence of epoxide. The results corroborate the unique organic-functionality-mediated cycloaddition mechanism, which provides important structure-function synergy in this unconventional route to non-redox CO2 fixation.

Original languageEnglish
Pages (from-to)3605-3620
Number of pages16
JournalInorganic Chemistry Frontiers
Volume10
Issue number12
DOIs
StatePublished - 4 May 2023
Externally publishedYes

ASJC Scopus subject areas

  • Inorganic Chemistry

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