Powder X-ray diffraction (XRD) patterns were collected on a Rigaku ATX-G workstation. Scanning electron microscopy (SEM) images and energy dispersive X-ray spectroscopy (EDS) measurements were collected on a Hitachi SU8030. N2 adsorption-desorption isotherms were collected at 77K on an ASAP 2020 instrument (Micromeritics). Inductively coupled plasma optical emission spectroscopy (ICP-OES) measurements were conducted on a Thermo iCAP 7600. UVvisible (UV-vis) absorption spectra of the digested thin films were collected on a Shimadzu 1601 UV-vis spectrometer. Diffuse reflectance UV-vis spectra (Shimadzu UV-3600) were collected from 1600 to 360 nm with a Harrick Praying Mantis diffuse reflectance accessory. Polytetrafluoroethylene (PTFE) powder was used as a reflector for baseline measurement. Diffuse reflectance infrared Fourier transform (DRIFT) spectra were collected on a Nicolet 6700 spectrometer equipped with an MCT detector. Liquid N2 was used to cool the detector during the measurements, and all DRIFT measurements were conducted at room temperature with Ar flow. KBr was used as a background spectrum. The steady-state emission spectra of NU-1000 and FeCN@NU-1000 were measured on a Photon Technology International (PTI) QuantaMaster 400 fluorometer. The samples were excited at 380 nm and emission spectra were monitored from 400 to 700 nm. Finely ground MOF crystals were used for the measurements. Cyclic voltammetry (CV) experiments were performed with CHI 900 potentiostat. A platinum coil and Ag/AgCl/KCl (3 M) electrode (BASi) were used as the counter electrode and reference electrode, respectively. The spin-coated thin film of FeCN@NU-1000 or NU-1000 deposited on an FTO substrate was served as the working electrode. The electrolyte was composed of 0.1 M NaClO4 aqueous solution.