Novel curcumin@HKUST-1 composite with enhanced visible light harvesting capacities for photocatalytic applications

The HKUST-1 and related MOFs have been proposed as photocatalysts, nevertheless they presented certain limitations, <i>e.g.</i> poor visible light absorption. Thus, we propose the encapsulation of the photosensitizer curcumin (Cur) in HKUST-1 as a strategy to improve light absorption in the resultant Cur@HKUST-1 composite. The Cur@HKUST-1 was characterized by XRD, FTIR, TGA, UV-Vis, BET, SEM, and electrochemical experiments confirming the Cur infiltration in 2.5%, preserving crystalline structure of HKUST-1. DFT calculations for Cur@HKUST-1 in periodic boundary conditions were employed to elucidate the chemical structure, corroborating experimental evidence. Chronoamperometry experiments in dark and visible light irradiation showed 48% photocurrent density enhancement for Cur@HKUST-1<i>vs.</i>HKUST-1, corroborating the sensitization effect derived from Cur inclusion. As a result, Cur@HKUST-1, presented 1.2 times (20% higher) photocatalytic hydrogen evolution than free HKUST-1 under visible light irradiation, just by 2.5% Cur loading into the HKUST-1, demonstrating infiltration as a suitable, nonlinear, strategy to produce active MOFs for photocatalytic purposes.