Influence of ZIF-8 polymorphism catalysts and nanosizes in p-nitrophenyl ester hydrolysis

Three ZIF-8 polymorphism structures (ZIF-L, n(21)ZIF-8 and n(35)ZIF) were synthesised by varying molar ratios of 2-methylimidazole and zinc nitrate hexahydrate (8:1, 21:1 and 35:1) in water at room temperature without any modulator. A high yield of up to 88% was produced for ZIF-L. Based on their distinct physicochemical characteristics, all were tested as catalysts for the hydrolysis reaction of p-nitrophenyl palmitate (p-NPPal) into p-nitrophenol (p-NP). The polymorphisms exhibited varying catalytic performance, which was related to altering the imidazolate linker. ZIF-L outperformed others up to 94 mu mol/min/g of p-NPPal hydrolysis at optimum conditions (1 w/v % of catalyst, incubated at 90 degrees C, 300 rpm for 15 min). Meanwhile, n(35)ZIF-8 with nanoscale particle (150 nm) demonstrated a good kinetics (R-2 = 0.99921) and recovery rate up to 78% by maintaining 50% activity until the fifth cycle.

Automated summary

Three different ZIF-8 polymorphism structures were synthesized with varying molar ratios of 2-methylimidazole and zinc nitrate hexahydrate. These structures were tested as catalysts for the hydrolysis reaction of p-nitrophenyl palmitate, with ZIF-L demonstrating the highest catalytic performance. Meanwhile, n(35)ZIF-8 exhibited good kinetics and recovery rate, maintaining 50% activity until the fifth cycle.