Visible‐Light‐Driven Photocatalytic CO2 Reduction to CO/CH4 Using a Metal–Organic "Soft" Coordination Polymer Gel. Issue 16 (21st February 2022)

• Record Type: Journal Article
• Authors: Verma, Parul; Rahimi, Faruk Ahamed; Samanta, Debabrata; Kundu, Arup; Dasgupta, Jyotishman; Maji, Tapas Kumar
• Is Part Of: Angewandte Chemie international edition. Volume 61:Issue 16(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-02-21
• Subjects: CO and CH4 Formation -- Coordination Polymer Gel -- Organogel -- Photocatalytic CO2 Reduction; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202116094
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: The self‐assembly of a well‐defined and astutely designed, low‐molecular weight gelator (LMWG) based linker with a suitable metal ion is a promising method for preparing photocatalytically active coordination polymer gels. Here, we report the design, synthesis, and gelation behaviour of a tetrapodal LMWG based on a porphyrin core connected to four terpyridine units (TPY‐POR ) through amide linkages. The self‐assembly of TPY‐POR LMWG with Ru II ions results in a Ru‐TPY‐POR coordination polymer gel (CPG), with a nanoscroll morphology. Ru‐TPY‐POR CPG exhibits efficient CO2 photoreduction to CO (3.5 mmol g −1 h −1 ) with >99 % selectivity in the presence of triethylamine (TEA) as a sacrificial electron donor. Interestingly, in the presence of 1‐benzyl‐1, 4‐dihydronicotinamide (BNAH) with TEA as the sacrificial electron donor, the 8e − /8H + photoreduction of CO2 to CH4 is realized with >95 % selectivity (6.7 mmol g −1 h −1 ). In CPG, porphyrin acts as a photosensitizer and covalently attached [Ru(TPY)2 ] 2+ acts as a catalytic center as demonstrated by femtosecond transient absorption (TA) spectroscopy. Further, combining information from the in situ DRIFT spectroscopy and DFT calculation, a possible reaction mechanism for CO2 reduction to CO and CH4 was outlined. Abstract : A porphyrin‐based coordination polymer gel (CPG) has been developed for visible/sunlight‐driven CO2 reduction. Notably, the product of CO2 reduction can be modulated by changing the sacrificial electron donor (SED). Ru‐TPY‐POR CPG upon photocatalytic CO2 reduction produces CO (3.5 mmol g −1 h −1 with >99 % selectivity in presence of TEA as SED), whereas in presence of both BNAH and TEA as SED, Ru‐TPY‐POR CPG produces CH4 (6.7 mmol g −1 h −1 with >95 % selectivity).