Hydrolytic dehydrogenation of ammonia borane in neat water using recyclable zeolite-supported cyclic alkyl amino carbene (CAAC)–Ru catalysts. (9th August 2022)

• Record Type: Journal Article
• Authors: Balla, Áron; Nagyházi, Márton; Turczel, Gábor; Solt, Hanna E.; Mihályi, Magdolna R.; Hancsók, Jenő; Valyon, József; Nagy, Tibor; Kéki, Sándor; Anastas, Paul T.; Tuba, Róbert
• Is Part Of: New journal of chemistry. Volume 46:Number 34(2022)
• Page Start: 16309
• Page End: 16316
• Publication Date: 2022-08-09
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/d2nj03334h
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : Highly effective ammonia borane dehydrogenation was carried out using a heterogenized ruthenium-CAAC complex in water. Abstract : Cyclic alkyl amino mono- and bis-carbene ruthenium (CAAC–Ru) complexes were immobilized on mesoporous Y zeolite (catalysts 3 and 4 ) and showed high activity and stability in ammonia borane (AB ) hydrolytic dehydrogenation. Both catalysts have a Ru content as low as 0.1 wt%. Catalysts 3 and 4 provide a reasonable activity even at a loading of 10 ppm (0.001 mol%) giving a turnover number (TON) of 79 000 molH2 molcat −1 . The optimal loading, however, was found to be slightly higher for catalyst 4, at around 50 ppm (0.005 mol%), giving a turnover frequency (TOF) of 8500 molH2 molcat −1 h −1 and a TON of 49 375 molH2 molcat −1 whilst retaining a high n H2 / n AB ratio (2.51). This value is higher than those observed for its homogeneous analogue 2 (TOF, 7500 molH2 molcat −1 h −1 ; TON, 43 600 molH2 molcat −1 ; released n H2 / n AB ratio, 2.18). Interestingly, it was found that the zeolite-supported catalyst gave a better performance than the non-supported water-soluble derivatives. No ruthenium leaching was detected for any of the zeolite-supported systems. Catalyst 4 showed a significantly higher activity than catalyst 3 and could be recycled up to 10 times. Catalyst 4 demonstrated a reasonable hydrolytic dehydrogenation activity even after three days in water upon exposure to air. The highest TON (79 000 molH2 molcat −1 ) obtained with catalyst 4 is equal to 1.68 kg H2 per gram of ruthenium metal.