Nickel containing polyoxometalates incorporated in two different metal-organic frameworks for hydrogen evolution reaction

Nickel containing polyoxometalates (POMs) K 6 NiSiW 11 O 39 ·15H 2 O ( 1 ), K 5 NiPW 11 O 39 . 15H 2 O ( 2 ), K 6 NiGeW 11 O 39 ·15H 2 O ( 3 ) are encapsulated in two different metal-organic frameworks (MOFs), i.e. MIL-100 (Fe) ( a ) and UIO-67 ( b ). As a result, six POM-MOF composites i.e. [H 6 NiSiW 11 O 39 ] 0.24 [Fe 3 C 18 H 7 O 14 ]·14H 2 O ( 1a ), [H 5 NiPW 11 O 39 ] 0.23 [Fe 3 C 18 H 7 O 14 ]·14H 2 O ( 2a ), [H 6 NiGeW 11 O 39 ] 0.26 [Fe 3 C 18 H 7 O 14 ]·14H 2 O ( 3a ), [H 6 NiSiW 11 O 39 ] 0.20 [Zr 6 O 4 (OH) 5.4 ][C 14 H 8 O 4 ] 5.3 .15H 2 O ( 1b ), [H 5 NiPW 11 O 39 ] 0.19 [Zr 6 O 4 (OH) 5.4 ] [C 14 H 8 O 4 ] 5.3 ·14H 2 O ( 2b ), [H 6 NiGeW 11 O 39 ] 0.19 [Zr 6 O 4 (OH) 5.4 ] [C 14 H 8 O 4 ] 5.3 ·13H 2 O ( 3b ) are fabricated and characterized via various analytical techniques. These composites are utilized as catalysts in photochemical and electrochemical hydrogen evolution reactions (HER). In photochemical experiments, 1a , 1b , 2a , 2b , 3a and 3b produced 9.2, 8.5, 11, 32, 45 and 30 µmols of hydrogen respectively; whilst generated a current density of 24, 17, 32, 80, 46 and 112 µA, respectively during electrochemical catalysis. Striking results of the detailed study show that when POM 3 is embedded in MIL-100 (Fe), it produces 45 µmols of H 2 compared to when embedded in UIO-67 (30 µmols). • Nickel containing polyoxometalates are encapsulated in MIL-100(Fe) and UIO-67. • Six POM-MOF composites are fabricated and characterized. • The composites are utilized as catalysts in photochemical and electrochemical hydrogen evolution reactions (HER). • K 6 NiGeW 11 O 39 embedded in MIL-100 (Fe) produces maximum 45 µmols of H 2 .