SHANGHAI, June 16 (Reuters) – China and the Asia Development Bank (ADB) have launched a green financing platform to support efforts by small- and medium-sized enterprises to cut pollution in the smog-hit Beijing-Tianjin-Hebei region, ADB said on Friday. The area, home to six of China’s 10 smoggiest cities in the first quarter of this year, has promised to upgrade or shut vast swathes of polluting industry as it tries to meet 2017 air quality targets. But financing the transition to cleaner energy has proved one of its biggest challenges, especially in poorer rural regions of Hebei, where the switch from coal to natural gas is expected to cost at least 300 billion yuan ($44.04 billion) over the 2016-2020 period. The financing platform was launched by the ADB and the China National Investment and Guaranty Corporation (I&G), the…