Water-soluble ruthenium complexes [(η6-arene)­Ru­(κ2-L)] n+ (n = 0,1) ([Ru]-1–[Ru]-9) ligated with pyridine-based ligands are synthesized, and the molecular structure of the representative complex [Ru]-2 is confirmed by X-ray crystallography. The studied complexes are employed for the catalytic dehydrogenation of formic acid in water. Screening of these complexes inferred that [Ru]-1 [(η6-C10H14)­Ru­(κ2-NpyOH-L1)­Cl]+ (L1 = pyridine-2-ylmethanol) outperformed others with an initial turnover frequency of 1548 h–1. Complex [Ru]-1 also exhibited high stability in water and can be recycled up to seven times with a total turnover number of 6050. In addition to formic acid dehydrogenation, [Ru]-1 also catalyzed the conversion of formaldehyde to hydrogen gas in water under base-free conditions. The effects of temperature, pH, formic acid, and catalyst concentration on the reaction kinetics are investigated in detail. Mass and NMR based mechanistic investigations inferred the presence of several important intermediate species, such as ruthenium-formate species [Ru]-1B and ruthenium-hydride species [Ru]-1C, involved in the catalytic dehydrogenation reaction. Moreover, the molecular structure of a diruthenium species [Ru]-1A′ is also authenticated by single-crystal X-ray crystallography.

Dehydrogenation of formic acid over various Ru‐arene complexes containing N‐donor chelating ligands was investigated in H2O and isolated and characterized several important catalytic intermediate species to elucidate the reaction pathway for formic acid dehydrogenation. Among the studied complexes, Ru‐arene complexes, namely [(η6‐C6H6)Ru(κ2‐NpyNH2‐AmQ)Cl]+ (C‐2), [(η6‐C10H14)Ru(κ2‐NpyNH2‐AmQ)Cl]+ (C‐3) and [(η6‐C6H6)Ru(κ2‐NpyNHMe‐MAmQ)Cl]+ (C‐4) [AmQ = 8‐aminoquinoline and MAmQ = 8‐(N‐methylamino)quinoline] were proved to be the efficient catalysts for formic acid dehydrogenation at 90 °C, even in the absence of base. With an initial TOF of 940 h–1, complex C‐4 displayed the highest catalytic activity for formic acid dehydrogenation in H2O and it can be recycled up to 5 times with a TON of 2248. Effect of temperature, pH, formic acid and catalyst concentration on the reaction kinetics were also investigated in detail. Extensive mechanistic investigations using mass spectrometry and NMR evidenced the formation of a coordinatively unsaturated species [(η6‐C6H6)Ru(κ2‐NpyNH‐AmQ)]+ (C‐2A)/[(η6‐C6H6)Ru(κ2‐NpyNMe‐MAmQ)]+ (C‐4A) as the active component during the catalytic dehydrogenation of formic acid. We further characterized the dimer‐form of C‐2A, possibly the catalyst resting state, by single‐crystal X‐ray crystallography.

To understand critical problems associated with solid waste and its consequences for the environment, a laboratory experiment is presented on the synthesis of aluminum-based metal−organic framework (MOF) MIL-53(Al) from household waste (PET bottles and aluminum foil/can), for undergraduate students of chemistry. This work is designed to teach students the research methodology and basic understanding of MOFs and their application in carbon capture and storage (CCS). Students also learnt several instrumentation techniques such as UV−vis spectroscopy, powder X-ray diffraction (P-XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and gas sorption to characterize the physicochemical properties of . The facile production of MIL-53(Al) enabled the students to investigate its applicability in CO 2 sorption. The calculations of essential parameters such as CO 2 over N 2 selectivity and the use of statistical tools in data processing are also explained to the students. In the end, the instructor presented his/her feedback by evaluating the answer sheets (pre-and postlab work) and by demonstrating the overall lab work through a model presentation.

A series of half sandwich arene–ruthenium complexes [(η 6-arene)­RuCl­(κ 2-L)]+ ([Ru]-1–[Ru]-10) containing bis-imidazole methane-based ligands {4,4′-(phenylmethylene)­bis­(2-ethyl-5-methyl-1H-imidazole)} (L1), {4,4′-((4-methoxyphenyl)­methylene)­bis­(2-ethyl-5-methyl-1H-imidazole)} (L2), {4,4′-((2-methoxyphenyl)­methylene)­bis­(2-ethyl-5-methyl-1H-imidazole)} (L3), {4,4′-((4-chlorophenyl)­methylene)­bis­(2-ethyl-5-methyl-1H-imidazole)} (L4), and {4,4′-((2-chlorophenyl)­methylene)­bis­(2-ethyl-5-methyl-1H-imidazole)} (L5) are synthesized. The synthesized and purified complexes ([Ru]-1–[Ru]-10) are further employed for hydrogen production from formic acid in aqueous medium. Among the investigated complexes, [(η 6-p-cymene)­RuCl­(κ 2-L2)]+ [Ru]-2, having Ru­(II) coordinated 4-methoxy phenyl substituted bis-imidazole methane ligand (L2), outperformed over others, displaying a higher catalytic turnover of 8830 and high efficiency (TOF = 1545 h–1) with appreciably high long-term stability for formic acid dehydrogenation in water.

Efficient catalytic systems based on arene-Ru(II) complexes bearing bisimidazole methane-based ligands were developed to achieve additive-free hydrogen generation from formaldehyde and paraformaldehyde in water. Our findings inferred the influential role of bis-imidazole methane ligands in the observed catalytic performance of the studied catalysts. Among the screened complexes, [(η 6 -p-cymene)RuCl(L)] + Cl − ([Ru]-2) (L = 4,4′-((2-methoxyphenyl)methylene)bis(2-ethyl-5-methyl-1H-imidazole) outperformed others to generate hydrogen gas from paraformaldehyde in water with an exceptionally high turnover number (TON) of >20,000. A detailed mechanistic pathway for hydrogen gas generation from formaldehyde has been proposed on the basis of identified several crucial catalytic intermediate species involved in the hydrogen production process.