**2. Materials and Methods**

#### *2.1. General Procedures*

Elemental analyses of (C, H, N) were performed on a PE 2400 series II CHNS/O (PerkinElmer Instruments, Shelton, CT, USA) or an Elementar Vario EL III analyzer (Elementar Analysensysteme GmbH, Hanau, German). Infrared spectra were obtained from a JASCO FT/IR-460 Plus spectrometer with pressed KBr pellets (JASCO, Easton, MD, USA). Thermal gravimetric analyses (TGA) were carried out on an SII Nano Technology Inc. TG/DTA 6200 over the temperature range of 30 to 900 ◦C at a heating rate of 10 ◦C min−<sup>1</sup> under N2 (SEIKO Instruments Inc., Chiba, Japan). UV–vis spectrum was performed on a UV-2450 spectrophotometer (Dongguan Hongcheng Optical Products Co., Dongguan, China). Emission spectra for the solid samples were determined with a Hitachi F-4500 fluorescence spectrophotometer (Hitachi, Tokyo, Japan). Gas sorption measurements were conducted using a Micromeritics ASAP 2020 system (Micromeritics Instruments Co., Norcross, GA, USA). Powder X-ray diffraction patterns were carried out with a Bruker D8-Focus Bragg-Brentano X-ray powder diffractometer equipped with a CuKα sealed tube (λ<sup>α</sup> = 1.54178 Å) at 40 kV and 40 mA (Bruker Corporation, Karlsruhe, Germany).

#### *2.2. Materials*

The reagent Zn(OAc)2·2H2O was purchased from SHOWA Co. (Saitama, Japan), Cd(OAc)2·2H2O from Fisher Scientific Co. (Hampton, NY, USA), Co(OAc)2·4H2O from J. T. Baker Co. (Phillipsburg, NJ, USA), and naphthalene-1,4-dicarboxylic acid (1,4-H2NDC) from Alfa Aesar Co. (Ward Hill, MA, USA). The ligand 4,4 -oxybis(N-(pyridine-4-yl) benzamide) (**L**) was prepared according to a published procedure with some modification [15].
