Try to compile it with
yum install git plesk-php70-devel make gcc openssl-devel
git clone https://github.com/mongodb/mongo-php-driver.git
cd mongo-php-driver/
git submodule update --init
/opt/plesk/php/7.0/bin/phpize
./configure --with-php-config=/opt/plesk/php/7.0/bin/php-config --with-mongodb-ssl=openssl
make
cp /root/mongo-php-driver/modules/mongodb.so /opt/plesk/php/7.0/lib/php/modules/
plesk bin php_handler --reread
After that in phpinfo() you will see:
libmongoc SSL enabled
libmongoc SSL library OpenSSL
libmongoc crypto enabled
libmongoc crypto library libcrypto