I have a best friend in my opposite gender. He is just a friend of mine, I don't have any sexual attraction towards him, we just talk as best buddies without touching each other. Is it haraam in Islam?
Is being friends with the opposite gender Haram? Obviously not but that does't mean anything goes. We also need to be careful when it comes to married couples. Both partners must have a clear understanding on the issue in general and each individual case must be looked at as well.
Beyond the above there is nothing stopping friendship between genders. We still have to to strictly follow the Quranic guidelines where any secret liaisons will have to be eliminated. All social interaction restricted to public places in general but if the intentions are good and the aim is to turn friendship into something more, then even a private meeting is permissible.
There are no restrictions on a work environment. Neither the Quran nor any mutawatir Hadith has placed such restrictions.
Beyond that Quranic laws have more than enough juice to ensure that nobody oversteps their limits.
The relevant verse where private meetings is permissible.
There is no harm in proposing in secret to (any of) these women, or keeping the intention to yourself: God is aware that you will keep them in mind. Yet do not make a promise in secret, unless you speak in a manner that is proper; and do not resolve upon marriage till the fixed term of waiting is over. Remember that God knows what is in your hearts; so be fearful of Him, and remember that God is forgiving and forbearing. Quran 2:235