Catalyzes the reversible oxidation of CO(2) and methanofuran (MFR) to N-formylmethanofuran (CHO-MFR). This enzyme is oxygen-labile. H2O + N-formylmethanofuran + 2 oxidized [2Fe-2S]-[ferredoxin] = CO2 + H(+) + methanofuran + 2 reduced [2Fe-2S]-[ferredoxin] One-carbon metabolism; methanogenesis from CO(2); 5,10-methenyl-5,6,7,8-tetrahydromethanopterin from CO(2): step 1/3. This enzyme is composed of six subunits FwdA, FwdB, FwdC, FwdD, FwdF and FwdG. By growth on tungsten or molybdenum under anaerobic conditions. Belongs to the FwdC/FmdC family.