Sintesis MOF Bimetal Berbasis Nikel-Kobalt dengan Ligan Asam Benzena 1,4-Dikarboksilat dan Modifikasinya dengan Etilendiamin sebagai Adsorben Campuran Gas CO2/CH4 = Synthesis of Nickel-Cobalt Based Bimetal MOF with 1,4-dicarboxylic Benzene Ligand and Its Modification with Ethylenediamine as Adsorbent for CO2/CH4 Gas Mixture